Capnography for Paramedics

2010 AHA Capnography Guidelines

2010-11-29T07:15:00.001-08:00

The new 2010 American Heart Association Guidelines now endorse wave form capnography as a Level I recommendation for ET tube verification, a Level IIa reccomendation for detecting return of spontaneous circulation and a IIb for monitoring CPR quality.

Part 8: Adult Advanced Cardiovascular Life Support

Here are the excerpts:

On ET Confirmation

Continuous waveform capnography is recommended in addition to clinical assessment as the most reliable method of confirming and monitoring correct placement of an endotracheal tube (Class I, LOE A).

Notes:

Waveform capnography should be used "to confirm and monitor endotracheal tube placement in the field, in the transport vehicle, on arrival at the hospital, and after any patient transfer to reduce the risk of unrecognized tube misplacement or displacement."

Studies on wave form capnography "have shown 100% sensitivity and 100% specificity in identifying correct endotracheal tube placement."

Colormetric ETCO2 devices should only be used "when waveform capnography is not available (Class IIa, LOE B)."

On Monitoring CPR Quality

It is reasonable to consider using quantitative waveform capnography in intubated patients to monitor CPR quality, optimize chest compressions, and detect ROSC during chest compressions or when rhythm check reveals an organized rhythm (Class IIb, LOE C).

On Indicating ROSC

If PETCO2 abruptly increases to a normal value (35 to 40 mm Hg), it is reasonable to consider that this is an indicator of ROSC (Class IIa, LOE B).

10 Things Every Paramedic Should Know About Capnography

2006-08-02T03:12:00.000-07:00

Capnography is the vital sign of ventilation.

By tracking the carbon dioxide in a patient’s exhaled breath, capnography enables paramedics to objectively evaluate a patient’s ventilatory status (and indirectly circulatory and metabolic status), as the medics utilize their clinical judgement to assess and treat their patients.

Part One: The Science

Definitions:

Capnography – the measurement of carbon dioxide (CO2) in exhaled breath.

Capnometer – the numeric measurement of CO2.

Capnogram – the wave form.

End Tidal CO2 (ETCO2 or PetCO2) - the level of (partial pressure of) carbon dioxide released at end of expiration.

Oxygenation Versus Ventilation

Oxygenation is how we get oxygen to the tissue. Oxygen is inhaled into the lungs where gas exchange occurs at the capillary-alveolar membrane. Oxygen is transported to the tissues through the blood stream. Pulse oximetry measures oxygenation.

At the cellular level, oxygen and glucose combine to produce energy. Carbon dioxide, a waste product of this process (The Krebs cycle), diffuses into the blood.

Ventilation (the movement of air) is how we get rid of carbon dioxide. Carbon dioxide is carried back through the blood and exhaled by the lungs through the alveoli. Capnography measures ventilation.

Capnography versus Pulse Oximetry

Capnography provides an immediate picture of patient condition. Pulse oximetry is delayed. Hold your breath. Capnography will show immediate apnea, while pulse oximetry will show a high saturation for several minutes.

Circulation and Metabolism

While capnography is a direct measurement of ventilation in the lungs, it also indirectly measures metabolism and circulation. For example, an increased metabolism will increase the production of carbon dioxide increasing the ETCO2. A decrease in cardiac output will lower the delivery of carbon dioxide to the lungs decreasing the ETCO2.

“CO2 is the smoke from the flames of metabolism.”– Ray Fowler, M.D. Dallas, Street Doc’s Society

PaCO2 vs. PeTCO2

PaCO2= Partial Pressure of Carbon Dioxide in arterial blood gases. The PaCO2 is measured by drawing the ABGs, which also measure the arterial PH.

If ventilation and perfusion are stable PaCO2 should correlate to PetCO2.
In a study comparing PaCO2 and PetCO2 in 39 patients with severe asthma, the mean difference between PaCO2 and PetCO2 was 1.0 mm Hg, the median difference was 0 mm Hg. Only 2 patients were outside the 5 mg HG agreement (1-6, 1-12). -Jill Corbo, MD, et al, Concordance Between Capnography and Arterial Blood Gas Measurements of Carbon Dioxide in Acute Asthma, Annals of Emergency Medicine, October 2005

“Research has (also) shown good concordance...in patients with normal lung function, upper and lower airway disease, seizures, and diabetic ketoacidosis.” –ibid.

V/Q Mismatch

If ventilation or perfusion are unstable, a Ventilation/Perfusion (V/Q) mismatch can occur. This will alter the correlation between PaC02 and PetCO2.

This V/Q mismatch can be caused by blood shunting such as occurs during atelectasis (perfusing unventilated lung area) or by dead space in the lungs (Ventilating unperfused lung area) such as occurs with a pulmonary embolisim or hypovolemia.

Normal Capnography Values

ETCO2 35-45 mm Hg is the normal value for capnography. However, some experts say 30 mm HG - 43 mm Hg can be considered normal.

Cautions: Imperfect positioning of nasal cannula capnofilters may cause distorted readings. Unique nasal anatomy, obstructed nares and mouth breathers may skew results and/or require repositioning of cannula. Also, oxygen by mask may lower the reading by 10% or more.

Capnography Wave Form

The normal wave form appears as straight boxes on the monitor screen:

But the wave form appears more drawn out on the print out because the monitor screen is compressed time while the print out is in real time.

The capnogram wave form begins before exhalation and ends with inspiration. Breathing out comes before breathing in.

A to B is post inspiration/dead space exhalation, B is the start of alveolar exhalation, B-C is the exhalation upstroke where dead space gas mixes with lung gas, C-D is the continuation of exhalation, or the plateau(all the gas is alveolar now, rich in C02). D is the end-tidal value – the peak concentration, D-E is the inspiration washout.

Abnormal Values and Wave Forms

ETCO2 Less Than 35 mmHg = "Hyperventilation/Hypocapnia"
ETC02 Greater Than 45 mmHg = "Hypoventilation/Hypercapnia"

Caution:

“End Tidal CO2 reading without a waveform is like a heart rate without an ECG recording.” – Bob Page “Riding the Waves”

However, unlike ECGs, there are only a few capnography wave forms. The main abnormal ones -- hyperventilation, hypoventilation, esophageal intubation and obstructive airway/shark fin -- are described below.

Part Two: Clinical Uses of Capnography

1. Monitoring Ventilation

Capnography monitors patient ventilation, providing a breath by breath trend of respirations and an early warning system of impending respiratory crisis.

Hyperventilation

When a person hyperventilates, their CO2 goes down.

Hyperventilation can be caused by many factors from anxiety to bronchospasm to pulmonary embolus. Other reasons C02 may be low: cardiac arrest, decreased cardiac output, hypotension, cold, severe pulmonary edema.

Note: Ventilation equals tidal volume X respiratory rate. A patient taking in a large tidal volume can still hyperventilate with a normal respiratory rate just as a person with a small tidal volume can hypoventilate with a normal respiratory rate.

Hypoventilation

When a person hypoventilates, their CO2 goes up.

Hypoventilation can be caused by altered mental status such as overdose, sedation, intoxication, postictal states, head trauma, or stroke, or by a tiring CHF patient. Other reasons CO2 may be high: Increased cardiac output with increased breathing, fever, sepsis, pain, severe difficulty breathing, depressed respirations, chronic hypercapnia.

Some diseases may cause the CO2 to go down, then up, then down. (See asthma below).

Pay more attention to the ETCO2 trend than the actual number.

A steadily rising ETCO2 (as the patient begins to hypoventilate) can help a paramedic anticipate when a patient may soon require assisted ventilations or intubation.

Heroin Overdoses - Some EMS systems permit medics to administer narcan only to unresponsive patients with suspected opiate overdoses with respiratory rates less than 10. Monitoring ETCO2 provides a better gauge of ventilatory status than respiratory rate. ETCO2 will show a heroin overdose with a respiratory rate of 24 (with many shallow ineffective breaths) and an ETCO2 of 60 is more in need of arousal than a patient with a respiratory rate of 8, but an ETCO2 of 35.

2. Confirming, Maintaining , and Assisting Intubation

Continuous end-tidal CO2 monitoring can confirm a tracheal intubation. A good wave form indicating the presence of CO2 ensures the ET tube is in the trachea.

A 2005 study comparing field intubations that used continuous capnography to confirm intubations versus non-use showed zero unrecognized misplaced intubations in the monitoring group versus 23% misplaced tubes in the unmonitored group. -Silverstir, Annals of Emergency Medicine, May 2005

“When exhaled CO2 is detected (positive reading for CO2) in cardiac arrest, it is usually a reliable indicator of tube position in the trachea.” - The American Heart Association 2005 CPR and ECG Guidelines

Reasons ETCO2 is zero: The tube is in the esophagus.*

* True as a general rule, but may not hold for cases of greatly prolonged down time prior to initiation of CPR or cases of massive pulmonary embolism where blood flow to the lungs is completely blocked. Also, in patients in arrest, CPR is neccessary to generate a waveform.

Caution: In patients with a prolonged down time, the ETCO2 reading may be so low (sometimes less than 6mm HG) that some monitor's apnea alarms may go off even though the monitor is still providing an ETCO2 reading and a small wave form. If the apnea alarm goes off and you continue to bag without resistance and have equal lung sounds and negative epigatric sounds, do not automatically pull your tube. A small but distinct square wave form along with even a marginal EtCO2 reading is still verification the tube is in the trachea.

ETCO2 can also be used to assist in difficult intubations of spontaneously breathing patients.

Paramedics can attach the capnography filter to the ET tube prior to intubation and, in cases where it is difficult to visualize the chords, use the monitor to assist placement. This includes cases of nasal tracheal intubation.

You're out (missed the chords).

You're in.

Paramedics who utilize this method during cardiac arrests with cardiac compressions continuing while they intubate may see CPR oscillations on the monitor screen immediately upon intubating, replaced by larger wave forms once the ambu-bag has been attached and ventilations begun. The oscillations provide proof that compressions alone can produce some ventilation.

Note: You must still assess for equal lung sounds. Capnography cannot detect right main-stem intubations.

Capnography can also be used for combitubes and LMAs.

Paramedics should document their use of continuous ETCO2 monitoring and attach wave form strips to their PCRs. Print a strip on intubation, periodically during care and transport, and then just prior to moving the patient from your stretcher to the hospital table and then immediately after transfer. This will timestamp and document your tube as good.

Continuous Wave Form Capnography Versus Colorimetric Capnography

In colorimetric capnography a filter attached to an ET tube changes color from purple to yellow when it detects carbon dioxide. This device has several drawbacks when compared to waveform capnography. It is not continuous, has no waveform, no number, no alarms, is easily contaminated, is hard to read in dark, and can give false readings.

Paramedics should encourage their services to equip them with continuous wave form capnography.

3. Measuring Cardiac Output During CPR

Monitoring ETC02 measures cardiac output, thus monitoring ETCO2 is a good way to measure the effectiveness of CPR.

In 1978, Kalenda “reported a decrease in ETC02 as the person performing CPR fatigued, followed by an increase in ETCO2 as a new rescuer took over, presumably providing better chest compressions.” –Gravenstein, Capnography: Clinical Aspects, Cambridge Press, 2004

“Reductions in ETCO2 during CPR are associated with comparable reductions in cardiac output....The extent to which resuscitation maneuvers, especially precordial compression, maintain cardiac output may be more readily assessed by measurements of ETCO2 than palpation of arterial pulses.” -Max Weil, M.D., Cardiac Output and End-Tidal carbon dioxide, Critical Care Medicine, November 1985

With the new American Heart Association Guidelines calling for quality compressions ("push hard, push fast, push deep"), rescuers should switch places every two minutes. Set the monitor up so the compressors can view the ETCO2 readings as well as the ECG wave form generated by their compressions. Encourage them to keep the ETCO2 number up as high as possible.

Note: Patients with extended down times may have ETCO2 readings so low that quality of compressions will show little difference in the number.

Return of Spontaneous Circulation (ROSC)

ETCO2 can be the first sign of return of spontaneous circulation (ROSC). During a cardiac arrest, if you see the CO2 number shoot up, stop CPR and check for pulses.

End-tidal CO2 will often overshoot baseline values when circulation is restored due to carbon dioxide washout from the tissues.

A recent study found the ETCO2 shot up on average 13.5 mmHg with sudden ROSC before settling into a normal range.-Grmec S, Krizmaric M, Mally S, Kozelj A, Spindler M, Lesnik B.,Resuscitation. 2006 Dec 8

Note: Each bar represents 30 seconds.

“End-tidal CO2 monitoring during cardiac arrest is a safe and effective noninvasive indicator of cardiac output during CPR and may be an early indicator of ROSC in intubated patients.” - American Heart Association Guidelines 2005 CPR and ECG

Loss of Spontaneous Circulation

In a resuscitated patient, if you see the stabilized ETCO2 number significantly drop in a person with ROSC, immediately check pulses. You may have to restart CPR.

The graph below demonstrates three episodes of ROSC, followed by loss of circulation during a cardiac arrest:

4. End Tidal CO2 As Predictor of Resuscitation Outcome

End tidal CO2 monitoring can confirm the futility of resuscitation as well as forecast the likelihood of resuscitation.

"An end-tidal carbon dioxide level of 10 mmHg or less measured 20 minutes after the initiation of advanced cardiac life support accurately predicts death in patients with cardiac arrest associated with electrical activity but no pulse. Cardiopulmonary resuscitation may reasonably be terminated in such patients.” -Levine R, End-tidal Carbon Dioxide and Outcome of Out-of-Hospital Cardiac Arrest, New England Journal of Medicine, July 1997

Likewise, case studies have shown that patients with a high initial end tidal CO2 reading were more likely to be resuscitated than those who didn’t. The greater the initial value, the likelier the chance of a successful resuscitation.

“No patient who had an end-tidal carbon dioxide of level of less than 10 mm Hg survived. Conversely, in all 35 patients in whom spontaneous circulation was restored, end-tidal carbon dioxide rose to at least 18 mm Hg before the clinically detectable return of vital signs....The difference between survivors and nonsurvivors in 20 minute end-tidal carbon dioxide levels is dramatic and obvious.” – ibid.

“An ETCO2 value of 16 torr or less successfully discriminated between the survivors and the nonsurvivors in our study because no patient survived with an ETCO2 less than 16 torr. Our logistic regression model further showed that for every increase of 1 torr in ETCO2, the odds of surviving increased by 16%.” –Salen, Can Cardiac Sonography and Capnography Be Used Independently and in Combination to Predict Resuscitation Outcomes?, Academic Emergency Medicine, June 2001

Caution: While a low initial ETCO2 makes resuscitation less likely than a higher initial ETCO2, patients have been successfully resuscitated with an initial ETCO2 >10 mmHg.

Asphyxic Cardiac Arrest versus Primary Cardiac Arrest

Capnography can also be utilized to differentiate the nature of the cardiac arrest.

A 2003 study found that patients suffering from asphyxic arrest as opposed to primary cardiac arrest had significantly increased initial ETCO2 reading that came down within a minute. These high initial readings, caused by the buildup of carbon dioxide in the lungs while the nonbreathing/nonventilating patient's heart continued pump carbon dioxide to the lungs before the heart bradyed down to asystole, should come down within a minute. The ETCO2 values of asphyxic arrest patients then become prognostic of ROSC.-Grmec S, Lah K, Tusek-Bunc K,Crit Care. 2003 Dec

5. Monitoring Sedated Patients

Capnography should be used to monitor any patients receiving pain management or sedation (enough to alter their mental status) for evidence of hypoventilation and/or apnea.

In a 2006 published study of 60 patients undergoing sedation, in 14 of 17 patients who suffered acute respiratory events, ETCO2 monitoring flagged a problem before changes in SPO2 or observed changes in respiratory rate.

“End-tidal carbon dioxide monitoring of patients undergoing PSA detected many clinically significant acute respiratory events before standard ED monitoring practice did so. The majority of acute respiratory events noted in this trial occurred before changes in SP02 or observed hypoventilation and apnea.” - -Burton, Does End-Tidal Carbon Dioxide Monitoring Detect Respiratory Events Prior to Current Sedation Monitoring Practices, Academic Emergency Medicine, May 2006

In the graph below, the respiratory rate decreases as the ETCO2 rises, and the patient suffers apnea, all the while the SPO2 remains stable.

Note: Each bar represents thirty seconds.

Sedated, Intubated Patients

Capnography is also essential in sedated, intubated patients. A small notch in the wave form indicates the patient is beginning to arouse from sedation, starting to breathe on their own, and will need additional medication to prevent them from "bucking" the tube.

6. ETCO2 in Asthma, COPD, and CHF

End-tidal CO2 monitoring on non-intubated patients is an excellent way to assess the severity of Asthma/COPD, and the effectiveness of treatment. Bronchospasm will produce a characteristic “shark fin” wave form, as the patient has to struggle to exhale, creating a sloping “B-C” upstroke. The shape is caused by uneven alveolar emptying.

Multiple studies have confirmed the sloping shape correlates to bronchospasm and obstructive lung disease.

“The analysis of the capnogram’s shape is a quantitative method for evaluating the severity of bronchospasm.” –You, Expiratory capnography in asthma: evaluation of various shape indicies, European Respiratory Journal, Feb, 1994

Changing Asthma Values

Asthma values change with severity. With a mild asthma, the CO2 will drop (below 35) as the patient hyperventilates to compensate. As the asthma worsens, the C02 levels will rise to normal. When the asthma becomes severe, and the patient is tiring and has little air movement, the C02 numbers will rise to dangerous levels (above 60).

Successful treatment will lessen or eliminate the shark fin shape and return the ETCO2 to normal range (Patient below: capnogram on arrival, after start of 1st combi-vent, after two combivents).

Hypoxic Drive

Capnography will show the hypoxic drive in COPD "retainers." ETCO2 readings will steadily rise, alerting you to cut back on the oxygen before the patient becomes obtunded. Since it has been estimated that only 5% of COPDers have a hypoxic drive, monitoring capnography will also allow you to maintain sufficient oxygen levels in the majority of tachypneic COPDers without worry that they will hypoventilate.

CHF: Cardiac Asthma

It has been suggested that in wheezing patients with CHF (because the alveoli are still, for the most part, emptying equally), the wave form should be upright. This can help assist your clinical judgement when attempting to differentiate between obstructive airway wheezing such as COPD and the "cardiac asthma" of CHF.

(wave form of patient with cardiac asthma)
7. Ventilating Head Injured Patients

Capnography can help paramedics avoid hyperventilation in intubated head injured patients.

“Recent evidence suggests hyperventilation leads to ischemia almost immediately...current models of both ischemic and TBI suggest an immediate period during which the brain is especially vulnerable to secondary insults. This underscores the importance of avoiding hyperventilation in the prehospital environment.” --Capnography as a Guide to Ventilation in the Field, D.P. Davis, Gravenstein, Capnography: Clinical Perspectives, Cambridge Press, 2004

Hyperventilation decreases intracranial pressure by decreasing intracranial blood flow. The decreased cerebral blood flow may result in cerebral ischemia.

In a study of 291 intubated head injured patients, 144 had ETCO2 monitoring. Patients with ETCO2 monitoring had lower incidence of inadvertant severe hyperventilation (5.6%) than those without ETCO2 monitoring (13.4%). Patients in both groups with severe hyperventilation had significantly higher mortality (56%) than those without (30%). –Davis, The Use of Quantitative End-Tidal Capnometry to Avoid Inadvertant Severe Hyperventilation in Patients with Head Injury After Paramedic Rapid Sequence Intubation, Journal of Trauma, April 2004

“A target value of 35 mmHg is recommended...The propensity of prehospital personnel to use excessively high respiratory rates suggests that the number of breaths per minute should be decreased. On the other hand, the mounting evidence against tidal volumes in excessive of 10cc/kg especially in the absence of peep, would suggest the hypocapnia be addressed by lower volume ventilation.” – --Capnography as a Guide to Ventilation in the Field, D.P. Davis, Gravenstein, Capnography: Clinical Perspectives, Cambridge Press, 2004

8. Perfusion Warning Sign

End tidal CO2 monitoring can provide an early warning sign of shock. A patient with a sudden drop in cardiac output will show a drop in ETCO2 numbers that may be regardless of any change in breathing. This has implications for trauma patients, cardiac patients – any patient at risk for shock.

In the study cited below, 5 pigs had hemorrhagic shock induced by bleeding, 5 pigs had septic shock induced by infusion of e-coli, and 6 pigs had cardiogenic shock induced by repeated episodes of v-fib. The pigs' cardiac output was continuously measured as well as their PETCO2.

“Cardiac output and PetCO2 were highly related in diverse experimental models of circulatory shock in which cardiac output was reduced by >40 % of baseline values… measurement of PetC02 is a noninvasive alternative for continuous assessment of cardiac output during low flow circulatory shock states of diverse causes.” -Xiahua, End-tidal carbon dioxide as a noninvasive indicator of cardiac index during circulatory shock, Critical Care Medicine, 2000, Vol 28, No 7

“A patient with low cardiac output caused by cardiogenic shock or hypovolemia resulting from hemorrhage won’t carry as much CO2 per minute back to the lungs to be exhaled. This patient’s ETC02 will be reduced. It doesn’t necessarily mean the patient is hyperventilating or that their arterial CO2 level will be reduced. Reduced perfusion to the lungs alone causes this phenomenon. The patient’s lung function may be perfectly normal.” --Baruch Krauss, M.D, JEMS, November 2003

9. Other Issues:

DKA - Patients with DKA hyperventilate to lessen their acidosis. The hyperventilation causes their PAC02 to go down.

“End-tidal C02 is linearly related to HC03 and is significantly lower in children with DKA. If confirmed by larger trials, cut-points of 29 torr and 36 torr, in conjunction with clinical assessment, may help discriminate between patients with and without DKA, respectively.” –Fearon, End-tidal carbon dioxide predicts the presence and severity of acidosis in children with diabetes, Academic Emergency Medicine, December 2002

Pulmonary Embolus – Pulmonary embolus will cause an increase in the dead space in the lungs decreasing the alveoli available to offload carbon dioxide. The ETCO2 will go down.

Hyperthermia – Metabolism is on overdrive in fever, which may cause ETCO2 to rise. Observing this phenomena can be live-saving in patients with malignant hyperthermia, a rare side effect of RSI (Rapid Sequence Induction).

Trauma - A 2004 study of blunt trauma patients requiring RSI showed that only 5 percent of patients with ETCO2 below 26.25 mm Hg after 20 minutes survived to discharge. The median ETCO2 for survivors was 30.75. - Deakin CD, Sado DM, Coats TJ, Davies G. “Prehospital end-tidal carbon dioxide concentration and outcome in major trauma.” Journal of Trauma. 2004;57:65-68.

Field Disaster Triage - It has been suggested that capnography is an excellent triage tool to assess respiratory status in patients in mass casualty chemical incidents, such as those that might be caused by terrorism.

“Capnography…can serve as an effective, rapid assessment and triage tool for critically injured patients and victims of chemical exposure. It provides the ABCs in less than 15 seconds and identifies the common complications of chemical terrorism. EMS systems should consider adding capnography to their triage and patient assessment toolbox and emphasize its use during educational programs and MCI drills.”- Krauss, Heightman, 15 Second Triage Tool, JEMS, September 2006

Anxiety- ETCO2 is being used on an ambulatory basis to teach patients with anxiety disorders as well as asthmatics how to better control their breathing. Try (it may not always be possible) to get your anxious patient to focus on the monitor, telling them that as they slow their breathing, their ETCO2 number will rise, their respiratory rate number will fall and they will feel better.

Anaphylaxis- Some patients who suffer anaphylactic reactions to food they have ingested (nuts, seafood, etc.) may experience a second attack after initial treatment because the allergens remain in their stomach. Monitoring ETCO2 may provide early warning to a reoccurrence. The wave form may start to slope before wheezing is noticed.

Accurate Respiratory Rate - Studies have shown that many medical professionals do a poor job of recording a patient's respiratory rate. Capnography not only provides an accurate respiratory rate, it provides an accurate trend or respirations.

10. The Future

Capnography should be the prehospital standard of care for confirmation and continuous monitoring of intubation, as well as for monitoring ventilation in sedated patients. Additionally, it should see increasing use in the monitoring of unstable patients of many etiologies. As more research is done, the role of capnography in prehospital medicine will continue to grow and evolve.

***
10 Things Every Paramedic Should Know About Capnography
Peter Canning, EMT-P
December 29, 2007 (Version 6.3)

Disclaimer: The information in this paper is gathered from textbooks, research articles, web sites, lectures and my own experiences. Paramedics should consult their medical directors and protocols for approved uses.

Capnography Web Resources

2006-08-02T03:06:00.000-07:00

1. Baruch Krauss

Baruch Krauss, M.D. of Boston Children's Hospital, is President of the Capnography Society and one of the leading advocates of capnography in the prehospital setting.

He is also the author of an excellent capnography article that appeared in the January 2003 issue of JEMS, the Journal of Emergency Medical Services.

Capnography in EMS

2. Emergency Medical Services Magazine

March 2005 article from Emergency Medical Services Magazine

Capnography In Sedation and Pain Management

August 2004 article:

Capnography as a Predictor of the Return of Spontaneous Circulation

3. Bob Page - Riding the Waves

If you are ever at an EMS Conference and get a chance to attend one of Bob Page's classes, do it. He taught a 12-Lead class at the CCEMT-P course I took a number of years ago and he was great! Funny, engaging and very informative. He has been teaching a class on capnography called "Riding the Waves" that I would love to take. In the meantime, you can download his 35-page handout for the course at the following link:

Bob Page's Download Page

Click on "capnography."

While there also visit his Capnography Waveforms

4. Capnography.com

Capnography.com is the most comprehensive capnography web site on the internet. Put together by Bhavani-Shankar Kodali M.D., an associate professor at Harvard Medical School, the site features everything from the science behind capnography to a wide array of sample wave forms. The site features a section called "Capnography in 911."

5. Biotel - Capnography Interpretation

This appendix, Capnography Interpretation comes from the BioTel Emergency Medical Service (EMS) System in Texas.

Capnography Interpretation

It does a nice job of capturing the basics in a short easy to understand format.

6. Capnography in the ER

Here is an excellent presentation by Rueben J. Strayer from McGill. The notes are very illuminating.

Slides

Slide Notes

7. End-Tidal CO2 Monitoring

Here's a link to an excellent powerpoint presentation by Paramedic Eric Augustus:

End-Tidal CO2 Monitoring

8. Capnographic Wave Forms in the Mechanically Ventilated Patient

An interesting article on capnographic wave form interpretation from Respiratory Care, January 2005.

Capnographic Wave Forms

9. Oridion

Oridion, a leading innovator in the capnography field, has capnography information on their web site.

Emergency Medical Services

10. Respironics Capnography CME

Respironics, one of the global leaders in capnography, offers a 1 hour Capnography CME on their web site. You have to create a user ID and password, then you can register for the capnography course, which is followed by a short quiz. In the end you can print out a CME certificate. I took the course, enjoyed it, and learned some new things about capnography. It does a very good job of describing the ventilation/perfusion mismatch issues. I recommend the class to everyone. Go to this web address to log in:

Respironics University

They also have capnography reference material posted at this site:

OEM Technologies Reference Library

11. Asthma

Here's the link to a site with some information about computerized capnography and asthma research.

Capnography Research in Asthma

12. Wikipedia - Capnography

Here's the Wikipedia entry for capnography, which could use some expansion.

Wikipedia: Capnography

13. National Guideline Clearinghouse Capnography Guideline

The National Guideline Clearinghouse™ (NGC) is a comprehensive database of evidence-based clinical practice guidelines and related documents. NGC is an initiative of the Agency for Healthcare Research and Quality (AHRQ), U.S. Department of Health and Human Services. NGC was originally created by AHRQ in partnership with the American Medical Association and the American Association of Health Plans (now America's Health Insurance Plans [AHIP]).

The NGC mission is to provide physicians, nurses, and other health professionals, health care providers, health plans, integrated delivery systems, purchasers and others an accessible mechanism for obtaining objective, detailed information on clinical practice guidelines and to further their dissemination, implementation and use.

Capnography/capnometry during mechanical ventilation: 2003 revision and update.

14. Physio-Control Capnography

Link to some good articles:

Capnography: Clinical Training Information

15. Capnography as BioFeedback
Interesting link about using capnography as biofeed back to teach people how to control their breathing.

CAPNOGRAPHY, BIOFEEDBACK, AND BREATH COACHING

16. Critical Care Nurse CEU Article on Capnography

Measuring End-tidal Carbon Dioxide: Clinical Applications and Usefulness

Clinical Studies

2006-08-02T02:40:00.000-07:00

Misplaced Tubes

Capnography as a Predictor of Rescusitation

Capnography and Cardiac Output

Capnography to Differentiate Cause of Arrest

Capnography and Sedation

ETCO2 and PaCO2 in Asthma

Identifying Airway Disease

ETCO2 and Mental Status

ETCO2 and Vantilating Head Injury

Capnography in DKA

Capnography and Trauma

Capnography and Gastroenteritis

Capnography and Critical Care Transport

Mainstream versus Sidestream Monitoring in the PACU

Comments

2006-08-02T02:39:00.001-07:00

Any comments or suggested links, please post here. Thanks. PC 12/22/2007

May 2007

2006-08-02T02:39:00.000-07:00

I continue to use capnography regularly on non-intubated patients. I have had two interesting calls lately.

CPAP -- The ETCO2 worked quite well through the CPAP mask on a patient in pulmonary edema. He was very tired when we got there with an ETCO2 of 50 that quickly came down to the 30's once we had the ETCO2 on. Unfortunately, I didn't get very good quality strips in the heat of the call.

Seizure -- We had a patient with a high blood sugar exhibiting stroke like symptoms who had a sudden seizure that I wrote about in Richter Scale. I had the ETCO2 cannula on initially and got a reading of 35, which made me think he wasn't in DKA. There was no Kussmal breathing or fruity acetone to his breath. He kept pulling the cannuala off, so we switched it to a regular 02 cannula, thinking the CO2 mouth flap was bothering him, then he started seizing. One of my crew managed to get the ETCO2 back on and it showed a sudden steady rise throughout the seizure from the 30's up to 69. After we broke the seizure with Ativan, his ETCO2 came back down to the 30's. Again, unfortunately, I wasn't able to get very good strips, but I did get part of the trend summary that showed the episode of hypoventilation during the seizure

insert trend Summary

His CO2 at the hospital was 22, which didn't square with what we were getting. Their diagnosis was DKA, although a review of the lab values and further study and suggestions from others have convinced me what he really had was Hyperosmolar Hyperglycemic Nonketotic Coma (HHNK).

April 2007 Log

2006-08-02T02:38:00.000-07:00

Faking a Seizure

I had a patient faking a seizure, who I wrote about in Wine Coolers. Bottom line, while he was thrashing about but his capnography showed regular respirations with an ETCO2 of 35. You can't be having a gran mal seizure and be breathing.

CHF-cardiac asthma

Did a call today for a man with dsypnea, wheezing and increasing edema over three weeks. His wife said the doctor increased his Lasix yesterday from 20 to 40 and gave him an inhaler. She said the inhaler wasn't working. The man had pitting edema up to his thighs, and could not breathe when he lay flat. I could hear some crackles. When we moved him from his wheelchair to the stretcher, the wheezing suddenly became very audible. I put him on the capnography.

Nice upright expiration wave form. I withheld a treatment and went with some nitro, which made him feel much better.

CPAP's Affect on Capnography

We just got CPAP so I ran a little experiment on myself, hooking myself up to capnography and then progressive forces of CPAP. For the most part CPAP had little affect on the reading, although the first time I did it, my ETCO2 dropped markedly because I wasn't holding a tight seal. Once I held a seal, the most I can say is CPAP made my ETCO2 go down slightly. When I factored in a slightly increased respiratory rate, I'd call it a wash.

Capnographs

I recieved the following from Eric at EMS Haiku, who is very knowledgeable in capnography.

Capnograph 1 is from an 11-month old child we were transporting to an out-of-town facility.

She had been diagnosed with bi-basilar pneumonia. As you can see, the wave forms are rounded on both sides. We were using a nasal cannula sampler.
Capnograph 2 is from the same child, after the prongs were readjusted to fit correctly.

You can see that the wave forms are much more normal, and that the EtCO2 value is 27, down from 34. I remember you talking about positioning of the sampler unit and degredation of the wave forms/values. I think this is a graphic example.

Capnograph 3 is from an adult.

We were called to a rural clinic to transport her to the local hospital. She had been diagnosed with bronchial pneumonia 10 days ago & given Cipro. She had worsening respiratory distress this morning and came into the clinic. Staff there had given her 2 Xopenex treatments w/o change. We arrived & put her on the EtCO2 and got this result. My partner (his first day practicing as a Paramedic) maintained the breathing treatment, and actually started a 3rd treatment (with Atrovent) during transport. There was absolutely no change in her presentation, clinical status, or EtCO2 by the time we got her to the hospital. We had talked about the fact that her EtCO2 was normal, and I did ask him later why he did the 3rd treatment. He basically said that it might have helped and he pretty much didn't know what else to do.
Anyway, some interesting stuff (at least to me, and possibly to you) to share. What it means to me is that 1) make sure the sampling prongs are inserted appropriately, and to trouble-shoot unusual wave forms, and 2) that EtCO2 really does indicate as well as rule out the need for breathing treatments.

Thanks, Eric.

Seizure

I had a seizure patient today who was just coming out of his postictal phase. I was taping down the IV when he started seizing again. While I went for the lock box to get the ativan, I tossed a capnofilter to my partner and asked him to put it on. It took about thirty seconds for him to do it, just as the seizure was subsiding. I could see right away the patient was breathing. His ETCO2 was 50. It soon went down to 33 as he recovered. I am going to try to put a capnofilter on all seizure patients now as soon as I get them so I will be able to capture a full seizureif they have another one.

Later today bored I tried to replicate the strips below. I was able to replicate the slow inspiration, but could not make myself breath in any way to create the pneumothorax strip. I'll be curious if I get another pneumo patient if the strip will look anything like that one.

Two Interesting Strips

80-year-old man from nursing home with a fever of 103. Aphasic from old CVA, history of aspiration pneumonia, vomiting this morning, the staff thinks he has aspirated. I hear rhonchi throughout. RR is 40. Sat 94% on 02. HR is 100. I'm thinking aspiration pneumonia. The wave form is a little odd. With that notch in the middle of the expiratory plateau. Same wave form throughout trip.

Turns out, he has a pneumonthorax.

2.

This is a man with a broken arm who got 12 mg of MS. While he is maintaining an ETCO2 of 34 with a RR of 12, and is alert, but subdued. His pain has gone from a 10 to hardly noticable. He has a long slow inspiration.

***

For other monthly logs, go to:

March Log

2006-08-02T02:36:00.000-07:00

Medtronic VHS Capnography Tape

I watched the Medtronic VHS Capnography tape today. It is about 8 minutes long and features Tim Phalen and Baruch Krauss. It is an introduction to nonintubated capnography for the person unfamiliar with it. Not a lot of information, but a clear start for novices.

More on CHF/COPD

I recieved the following comment on the CHF/COPD question. I think it is an excellent explanation:

I haven't been using capnography long, but here is my interpretation of the CHF waveform. I have only seen upright waveforms, even with wheezing. The wave form, as we have been told, is due to uneven alveolar emptying caused by constriction of the bronchioles. This constriction is obviously not the same thoughout the lungs, which leads to the uneveness. In CHF, the bronchioles "stiffen" up to protect against the fluid. This causes the wheezing (not constriction). Since the bronchioles are relatively the same size, alveolar emptying is rather even-therefore a decent waveform. I know what you are thinking........what about the fluid. You maybe thinking the fluid may cause uneven emptying. I disagree. If fluid is in the bronchioles, then it has collapsed the distal alveoli and no gas exchange will be taking place- therefore no uneven emptying.

This is just my thoughts. Mike S.

Hyperventilation

We got called to a treatment facility for a just admitted patient who couldn't feel her legs. We found a twenty-two year old breathing eighty times a minute. We tried to get her to slow her breathing down, but that wouldn't work. She was up on the third floor of a residential setting, but the elevator was broken, so we tried to help her walk, but she said she couldn't. We made it down on flight, and then I just said to a first responder, we need to carry her. I took her upper half and he took the lower half and we carried her the rest of the way. I leaned against the wall as I went down the stairs for support. The other medics thought I was too nice to be carrying her. In the ambulance, I put her on the capnography and her ETCO2 was 20 and her RR was 50-80. For experiments on myself, I know if you can even get your ETCO2 down to 20 and are breathing that fast, you probably will be dizzy and unable to feel your legs.

I patched the call in as hyperventilation. When we wheeled the patient in, the nurse (one who is always sarcastic) shouted across the ER -- "You have her on an oxygen cannula! Do you need a mask?" She said it in a belittling way like she's just hyperventilating, she doesn't need oxygen. After I unloaded the patient I went up to her and said, "For your education, this is not oxygen. It is capnography. It measures her respitratory rate and her ETCO2, which is 20. It provides objective proof of hyperventilation." "Oh, oh, I didn't know," she said.

Patient with Trach

I had a patient today with a trach, fever of 103 and history of respiratory failure. I popped an ET capnofilter on her trach, even though she could breath on her own (she had blow by 02), and it gave an excellent reading and wave form. No need to attach an ambubag.

State Conference

I taught a class at the state conference on capnography. I saw a couple people nodding off. I advertised the class as Capnography for Paramedics and EMTs, but I think I might have been over the heads of some of the EMTs. It takes me awhile to understand concepts, but then once I have them, they seem easy. I need to show the same patience when I teach. Teaching is also always harder than I imagine it. I try to tell them everything I know in an hour and a half and I think I end up rushing. But each time I teach, I figure out a better way to do it. It is also hard when I compare myself to Bob Page's presentation. I can do better than I did, but will have a hard time matching his class.

Sleep Apnea

I did an interesting call written about in A Nap. The bottom line was a barely responsive patient with an ETCO2 of 64-70. She had a history of sleep apnea, and was in fact, just sleeping deeply. Patients with sleep apnea are at risk for hypoventilation because they stopped breathing until they wake themselves up.

March 9, 2007 - Capnography Vendors at JEMS

I walked about the EXPO hall looking specifically for capnography and was disappointed to see it displayed so poorly.

The Physio-Control booth had a table with some literature/handouts on capnography, which was good. I talked briefly there with a person from Oridion, which manufactures the capnofilters that Physio uses.

Phillps Medical Systems also had some Oridion filters out, but not much promotion of the capnography in their monitors. I did have a very pleasant talk with one of their salespeople about capnography.

The Respironics booth had CPAP and a small capnography monitor, but every time I walked by they were demonstrating CPAP.

Zoll, which in Las Vegas sponsored Bob Page’s half hour class on capnography in their demo theatre, had nothing visible.

I did encounter a new product from a company called Nonin, which had a product called Lifesense Capnograph, which had a interesting capnography screen. They also advertised their product as having first breath capability.

I also queried the booksellers about capnography books.

Brady Books actually had Bob Page there at the time I stopped by and he said his book will be out late next year. The Mosby salesperson had no books they knew about. Jones and Bartlett Publishers said they were in discussion with some people about writing one, but had nothing definite.

Jems Conference - Bob Page "Slap the Cap!

Highlights from Bob Page’s Slap the Cap Cagnography Presentation

I attended Bob Page’s hour and a half version of his famous capnography class. Last year in Las Vegas I saw the half hour condensed version. I envy anyone who has been able to attend his half day course. He is a phenomenal educator/entertainer.

People filtered into the classroom before show time to see Queen and then Billy Joel performing on the big screens set up in the front of the room. When Bob Page appeared to start the class, he humbly thanked his opening acts...Queen and Billy Joel.

Page calls capnography an “upgrade,” and to illustrate this he describes his first airline upgrade to first class and how he found out the drinks were unlimited, you could be served before the plane took off, you got peanuts, cashews and pistachios in a bowl rather than a tiny bag of salted peanuts and you also got warm moist lemon scented towels. Like first class on an airplane, capnography gives you stuff that you can’t get in coach.

Before getting into what that stuff is, he does a great demonstration of a blood cell carrying carbon dioxide in which he plays the blood cell running through the body. He simulates what happens to him during cardiac arrest, during a PE, and during a hemorrhage how he is thrown out of the body, and describes the effect of that all on the end tidal C02.

I’m not going to go through his entire class, but I will point out the key points from his presentation that I found personnaly found valuable or helped clarify my own thinking on the issue.

1. While most people use the definition of hyperventilation and hypoventilation to describe low and high ETCO2 numbers, he uses the terms hypocapnia and hypercapnia, which may be a more accurate was of describing it.

2. He does a killer job of trashing colorimetric capnography devices and the turkey baster/bulb syringe by reading their instructions and then applying them to real situations. For instance, the colorimetric says you must give six breaths to determine the reading to make certain all of the carbon dioxide is out of the stomach. Well six bags into the stomach is going to visually tell you there is a problem before the device does.

3. He takes about the wave form you will get from an intubated patient who is coming out of sedation before they start bucking the tube, so you can get out more sedation before they actually buck the tube. It is another example of how capnography makes you proactive as opposed to reactive.

4. He talks about asthma and makes the point you can’t fake a broncospasm/shark fin wave form. Anyone who says they are having an asthma attack and is trying to make a wheezing sound deliberately will have a straight up wave form unless they are actually having an asthma attack.

5. He calls wave form capnography a “one stop tube confirmation stop.” Technically, it is a two stop shop, because you still have to listen to lung sounds to make certain you don’t have a right mainstem intubation, which won’t show up on capnography. Still a desciptive phrase, meaning you don't have to go through all the step you might otherwise have to use if you didn't hve capnography.

6. He suggests hitting record on your intubated patients right before you move them to the ED’s stretcher and then immediately after you have moved them over to time stamp your intubation in case the ED says your tube is no good.

7. On the issue of ventilation rate, while the new AHA guidelines specify the rate as 8-10 for a patient in arrest and 10-12 for an intubated patient, you should instead use the capnography as your guide. If their ETCO2 is 70, you might want to increase your ventilation rate to blow some of that CO2 off.

8. Finally, before I could ask, he addressed the COPD/CHF question and his take is if the wave form is upright, there is no obstruction, so the wheezing is caused by the CHF, not the COPD, so you might want to withhold the neb treatment.

There is obviously much more to the class than this. As I have said before, if you ever get a chance to attend one of his courses, do it, he is great.

In the meantime, you can download his 35-page handout for the course at the following link:

Bob Page's Download Page

Click on "capnography."

While there also visit his Capnography Waveforms

***

I saw Bob Page later at the Brady books booth. I asked him about the CHF/COPD and he said definately an upright waveform is CHF. The wheezing is from the rales in the bases, but it is not widespread like with COPD, which will cause the extended uneven emptying and the shark fin shape.

February 2007 Log

2006-08-02T02:35:00.000-07:00

February 26, 2007 - CHF/COPD? One, the other, or both?

70 year old man with increasing dsypnea while on diaylsis. History of COPD/CHF. Respiratory rate is in the high 40's. BP 180/100. HR - 112. Sat 90 on 02 by cannula at 2 lpm. No chest pain. ETCO2 38. Upright wave form. Lung sounds -- rales in the bases, with some wheezing. No pedal edema. Man takes 80 mg of Lasix daily. Also on inhalers. Says he has never had trouble breathing quite like this before.

I put the man on a nonrebreather which brought his SAT up to 100%, gave him 3 nitros and one albuterol by neb shoved under the nonrebreather. His ETCO2 went up to 45 but then held steady. RR came down to 38-40.

At the hospital, one doctor thought it was COPD, the other thought there might be some CHF or at least a combination. They gave him nitro paste and a combivent along with some steroids, and ordered a chest x-ray.

The one doctor said the man shouldn't be on the mask because he had COPD. I mentioned his ETCO2 had been holding steady at 45. He looked at me like I was from outerspace. Later he looked the man's records up (the man had been there a month ago for exacerbation of COPD) and announced the man wasn't a retainer. (By saying his ETCO2 was holding steady at 45 I was trying to tell him that.) They did put the man down to a cannula and after a minute, a nurse announced he was satting fine on the cannula at 97. I said, I thought it might drop more.(A minute isn't long enough to desat from 100%). It went down to 94, and then they had the treatment ready for him.

He was doing a little better by the time I left. Was it the nitro? the treatment? or both? I don't know. I wish I could follow up. While one of the doctors thanked me and said good job, I was a little frustrated because I had the capnography, which was providing information, but I felt there was a language barrier between the ED staff and me that prevented me from effectively sharing the information.

I don't want to seem like a wise guy, which is my worry when I try to talk about capnography to someone unfamiliar with it. Who am I to tell a physician or nurse (who I may not know well) something about their patient by bringing up a technology they haven't been trained in or may misunderstand? It is hard to do it. Sometimes they listen, sometimes they are dismissive, most of the time they just say nothing.

1. The capnography seemed to be saying that the problem is perhaps CHF rather than COPD because the wave form is upright. The alveoli are emptying evenly? I just don't know enough yet to be able to say this is true, but it has me thinking.

2. The capnography was saying high-flow 02 is okay because the patient doesn't have a hypoxic drive -- the ETCO2 was constant in the normal range.

I'm not criticizing the hospital or particuarly their care so much as wishing they had capnography, and some education about it so they can make use of (consider) what could be valuable information.

I am also frustrated because I wish more was written about capnography (why I eagerly await the books of Krauss and Page) so I could have some reference to sort some of this out. I am doing my best to understand it, but my expertise is largely self-taught and based on a limited field of research, as well as field observation. I worry sometimes that I am getting it wrong.

One question I want to pursue is capnography and wheezing. When can you have a wheeze and an upright wave form? What type or degree of wheeze will produce an upright waveform? Can it be true, as I am speculating, that "cardiac asthma" wheezes induced by fluid overload will not produce the typical shark fin, but will be more straight up, while obstructive airway wheezes will have the shark fin shape? If this can be proved by a study, it can be a valuable diagnostic tool. I will query some MDs about that. Any thoughts are welcome.

I found the following discussion on a forum at emsvillage.com where one medic says he uses the wave form to distinguish between COPD and CHF.

Cardiac versus Respiratory Wheeze

February 25, 2007 - Cannula Positioning

Today I had an elderly patient with CHF. The initial end tidal was 8, but quickly jumped to 30 when I repositioned the cannula because the patient was a mouth breather. I put a non rebreather on and the number went down to 20. Several times during the call, the numbers moved, and each time when I repositioned the device the numbers came back to near 30.

(The other day I heard a medic patch in with a patient with stable vital signs but an ETCO2 of 9. Positioning of the cannula was probably the issue.)

The point of all this is that positioning the cannula is very important if your reading doesn’t seem right. It can be affected by a patient’s unique anatomy, by the patient’s method and manner of breathing and by their anxiousness during transport, which can shift the cannula position. (The position will affect not only the ETCO2 number but the RR number.) This patient had an initial RR of 48, which gradually came down to 38 due to some NTG SL, which seemed to help the breathing. The ETCO2 rose to 32, and settled there, which I was happy with considering. I stayed alert to make certain the RR wasn’t declining due to the patient growing more tired. Her effort in breathing seemed a bit more relaxed.

This all goes along with what I wrote below about normal values. You can't just always accept the numbers at face value and compare them to traditional norms.

February 20, 2007 - Normal Values

The normal values for ETCO2 are listed at 35-45 mm Hg. I have read that they are really 33-43 due to the possible gradient between arterial Co2 and ETCo2. What is normal anyway? Normal HR is 60-80, Bp 110/70-130/80. It all depends on the person obviously. But as I don't get too concerned with a HR of 88 or a BP of 140/90, I think you have to take the same approach with ETCO2. Most of my patients have ETCO2 in the 28-35 range, it seems. It is an emergency situation and usually they are a little short of breath -- that accounts for it. Sometimes the 02 dilutes it a little. I guess all I'm saying is normal is different for everyone to a point, and that in the emergency setting, it is not uncommon to have many people outside the normal range. I am most concerned with extreme readings that are trending worse.

February 18, 2007 - Cheyene-Stokes

Another medic shared her strips with me. 65 year old with sudden onset altered mental status whose GCS dropped from 10 to 4 early in the call, and who began exhibiting Cheyene-Stokes respirations with periods of apnea.

February 17, 2007 - Hospital Capnography Skill Sessions

Yesterday I taught a skill station on capnography at one of the area hospitals, which was having an education day for nurses. Many of the nurses were from the ED. I was paired with the vendor for Nellcor, which provides the hospital’s Hand Held Capnographs.

I passed out copies of the 10 Things Every Paramedic Should Know About Capnography handout as well as another handout I made called What We’re Talking About-EMS/ED Capnography Interaction, which I hope to soon post here.

The nurses were very interested in this new technology and most of them wondered why they had either never heard of it, or why they only had two machines in the ED. We had a interesting discussion with them. We talked about the costs of capnography and one nurse pointed out how, if capnography can help you decide who needs intubation and who doesn’t, it can save enormous costs both financial and human, not to mention the protection that capnography provides from the costs of an unrecognized misplaced airway.

It was interesting hearing some of the vendor's experiences with other facilities trying to convince them of the benefits of capnography. We decided that if you have capnography, it’s like having Windows while the rest of the world is still using MS- DOS.

It will be interesting to follow up with the nurses in a few weeks and see if they have used the capnography or how their interactions with medics bringing in patients on capnography have changed.

I’m hopeful the hospital will hold more sessions like this one in the future.

February 3, 2007 - Capnography Conversations with Another Medic

I had a long talk with another medic, who uses capnography even more than me. He says he puts it on every ALS patient and some BLS patients simply because it is another source of information to help with the clinical picture. He was telling me about a call for CO posioning. The patient was feeling light-headed and dizzy. The fire department did a sweep of the house and their machine came up with nothing. The ETCO2 was reading 50 even after fifteen minutes of 02 by nonrebreather on an extremely healthy fifty-year old man. The medic asked the fire department to do a more thorough sweep or else their meter had to be off -- something wasn't right. He compared the capnography that is calibrated every day and used all the time in a $25,000 machine versus their machine that sits in a cold truck and isn't used or calibrated much. The fire chief didn't understand what the medic was talking about because he was monitoring for CO and the medic was talking about CO2. Anyway, it turns out the guy had been moving cars in the garage and had left one of them running for awhile and it had sent up a big spray of white smoke while he was running it, and it must have all wafted into the house. I didn't get the whole rest of the story, but I think the point was while the fire department was poo-pooing there being a problem, the capnography was showing that there was something off with the man's ventilation, and in an otherwise healthy man, it was signaling something had happened to change his norm. The C0 was affecting his ETCO2.

I did an internet search to try to find any articles describing a relationship between ETCO2 and CO, and came up dry except for a research grant that listed "Relationship between EtCO2 and carboxyhemoglobin in carbon monoxide" as a topic for study.

Sometimes I think the best use of ETCO2 is to alert us to an as yet unseen problem so we can be vigilant and question what is going on. In this case, instead of poo-pooing the man's symptoms in light of non-CO readings, keeping him on 02 and transporting.

The medic said he found capnography very useful in seizure patients to learn if he needs to ventilate them and for use in patient's having psuedo-seizures. They may be flopping around, but if the capnography shows they are breathing during this episode it can demonstrate they are not having true gran-mal seizures where they would not be breathing.

He also said he has had the same apnea alarm problems I have been having on codes when the ETCO2 is low in the 6 and less zone.

January 07 Log

2006-08-02T02:34:00.000-07:00

Oscillations and Apnea Alarms

I did another code that I describe in The Man Who Wouldn't Die Part 2.

Two interesting things from the capnography perspective.

First, the oscillations from CPR captured on intubation prior to the first ET ventilation.

To me these oscillations are proof CPR alone provides some small amount of ventilation itself.

Second, I am getting annoyed with my LP 12. The apnea alarm contines to go off doing codes if the ETC02 gets too low. The machine cannot be programmed to adjust the apnea alarm. It goes off whenever it can't detect a decent breath. The alarm is hard to ignore, and very frustrating during a code. I kept having to recheck my tube, which was good by every measure. I have talked to other medics who have the same problem. Later on the printout I can see a small waveform, but it is hard to make out sometimes during the code. My almost 50 year old eyes maybe are at fault. Anyway, as long as the ETCO2 number is reading a number, then the tube should be good. The alarm is only useful when it is announcing a surprise change in the trend, but when the ETCO2 is low, it is a pure pain. It seems to go off around 6-7. The machine registered the ETCO2, but does not read any respirations for some reason.

?Pneumothorax

A medic told me a story of a call he did where he was transporting a patient who had just been intubated at a satellite clinic and had been a difficult and apparently violent intubation. En route to the hospital, the patient's ETCO2 started rising from 35 steadily up into the 50's, 60's, and then 70's. He and his partner, another medic, discovered the patient had no lung sounds on the left side. They decompressed the patient, and the ETCO2 went back to 35 with good compliance and equal breaths sounds.

At the hospital, they caught hell from a ED staffer, who suggested they had caused the pneumo and the reason they hadn't heard lung sounds was the patient had a right mainstem intubation, and that capnography doesn't tell you anything, anyway. I wasn't there so I may not be accurately reporting what the ED staffer actually said.

From the medics' side, they are two excellent medics who were alerted to a problem, troubleshot it, took action, and resolved the problem.

I subsequently went to capnography.com (under the frequently asked questions) and read about how capnography may be affected by either a tension pneumo or a endobroncial intubation. The bottom line was the capnography is non-diagnostic in these cases and can go either way depending on many variables. For instance, a pneumo may cause the ETCO2 to rise, but once it becomes a full-fledged tension that is inhibiting cardiac output, it will cause the ETCO2 to fall.

The lesson to be learned from the call is that ETCO2 monitoring may alert you to a possible problem before it becomes critical, and then cause you to troubleshoot as these fine medics did, and then take appropriate action.

As far as the hospital's response, it may just be a matter of education and use. Some staffers are very receptive, some seem ignore it(not hearing you), and some may be outright dismissive. In time, that will change. Later next month, I will be teaching a skill session at one of the hospitals for the ED staff to educate them about capnography.

Cardiac Arrests

I backed up another unit on a code. 58 year old female went into arrest in her driveway. Cops arrived quickly, shocked patient. Medic arrived patient had her own respirations. He intubated her and had her in the back of the ambulance by the time I got there. He was just putting the capnography on. Good wave form. ETCO2 was 51 that gradually came down to 35. Her BP was 78/40 to start by was 140/80 by our arrival. Her heart was in an afib in the 120-130 range. All we gave her was 300 cc of fluid. At the hospital I asked the medic to make a point of describing the capnography in the course of his report and not to detach it until the doctor had checked the lung sounds. I was curious to see whether the doctor would be looking for the capnography, be inquisitive about it or just ignore it.

Neither the doctor or the respiratory therapist even looked at it. The doctor was concerned about feeling a pulse. He did check lung sounds and announced the tube was good. Finally the EMT unhooked the monitor and capnoline. The medic included the capnography in his verbal report but I saw no reaction in the doctor's eyes to the information. The patient was not hooked up to the hospital's capnometer. At least the doctor didn't use a colorimetric device to check the tube.

Later in the day I did a code at a nursing home. Another 90 year old cancer patient in asystole. This time I recorded the cardiac ossilations I saw immediately on intubating from the effect of CPR on the lungs(causing little tidal volume waves before I had attached the ambu bag and started the first ventilation (shown below).

My initial ETCO2 was 14, but it soon went down to the 5-8 range. Again a couple times the apnea alarm went off and the machine was not registering respirations despite a solid tube.

It was very annoying. We called the code after a half an hour. I would have called it sooner, but it took awhile to get an IV and get drugs in the patient.

ROSC

Another medic, who is just learning about capnography like many of us, showed me his strips from a cardiac arrest and wondered about the strange uplift in the ETCO2 he saw. He said at one point he got a BP with the automatic cuff but didn't trust it since he couldn't feel a carotid pulse. CPR was continued throughout.

Here are the strips, vital signs and trend summary.

Initial rythmn at 18:33:

Rhythm at 18:46 just before spike in ETCO2. ETCO2 is 28.

Vital sign summary: Note at 18:48 ETCO2 is 56. At 18:55 The BP cuff reads 126/100.

Trend Summary:

So what happened? The trend summary shows the classic overshoot of ETCO2 that occurs when a patient experiences ROSC. It looks like the patient had spontaneous circulation for several minutes -- possibly up to 8 minutes. I will try to get more details of the call when I see the medic next. I believe the patient was declared dead at the hospital.

More info to follow.

Pediatric Wheezing

11 year old boy with sudden onset dsypnea. No history of asthma found tripoding and with expiratory wheezes.

Breathing much better after two albuterol treatments with just slight expiratory wheeze.

DKA

50 year old female, slightly disoriented, difficulty breathing. ETCO2 - 17. RR- 30-50. Here's the strip and trend summary:

No history of diabetes, but recently put on prednisone.

Blood sugar - 600.

Arrest

I intubated a tiny old man in cardiac arrest. When I first looked for a wave-form, I had a bazillion tiny ocillations on the screen. I'm kicking myself for not hitting the print button right away. The osillations were actually the CPR. I had them stop the CPR for a moment, trying to figure out what was going on. The ETCO2 number popped up then as 20, but the RR rate showed 83, which again was the CPR.

We cracked a couple ribs right off the back and the end tidal number went down quickly. Three epis and two atropines brought no response. By now the ETCO2 was in the 4-8 range.

I presumed the patient after 20 minutes of ACLS.

The call was a little frustrating from the monitor standpoint. The apnea alarm kept going off and I kept having to check the tube, which was perfect. I can only guess that the inital high number was do to CO2 built up in the nonventilating lungs while the patient bradyied into arrest before our arrival, and that the low ETCO2 was due to inability to get any output going with CPR and the broken ribs or maybe the person had been down awhile.

He was wheelchair bound and found unresponsive and likely not breathing by his caregivers.

For other monthly logs, go to:

December Log

2006-08-02T02:33:00.000-07:00

Cannula Placement

I had a 60 year old dialysis patient with a high fever and altered mental status, hypotension and a low Sat. I put the end tidal on and got a reading of 11, which didn't seem right. I noticed he was a mouth breather with a large upper lip. I shifted the mouth piece downward and walla, the end-tidal was 53. This has happened several times now. See the September log for a photo of the problem, as well as the exampe in the December 11 call below. I put the patient on a nonrebreather. At the hospital when I was giving my report to the doctor, I mentioned the patient's ETCO2 was 53, to which she snapped, he probably doesn't need to be on a nonrebreather then. ??? There is no COPD history here. This is a patient with a fever of 102.8, which might account for the high ETCO2 and a cannula air SAT in the 80s.

Seizure/Hypoventilation

Called for a seizure. We found a postictal 80 year old man. No prior historyof seizure, who they said fell the night before, but hadn't appeared injured. Out in the ambulance he started seizing again. I managed to get a 24 gauge in his arm just as he stopped seizing. I had the ETC02 on and was watching his respirations now. He didn't look like he was breathing. It was more sort of burping.

I'm not certain what the little bumps represented -- the burps possibly, but I believe now I just had the cannula too deep in his nose and not enough over his mouth. I repositioned it, as he started taking deeper breaths. His end tidal was 80.

His breathing was very irregular, sporadic.

I kept waiting for him to snap out of it, but he wasn't coming around. I tried bagging him for a little bit, and then decided just to intubate him. I attached the capnography filter to the top of the ET tube, put in the stylet and went in. Saw the chords, saw good wave form on the monitor and I was good. I bagged him and got his ETCO2 down to 35.

He started bucking the tube a little so I gave him some versed.

At the hospital they said he had been in the hospital for a subdural hematoma a month before, so he may have been bleeding again.

Here's the trend summary for ETCO2 and RR:

Note: The apnea period includes a period where his nasal monitor is off and the ET tube isn't in yet. I have to unplug one filter, plug in the other and then I won't start getting a reading until I go in with the tube.

What lesson did I learn from the capnograpy? It alerted me that he was hypoventilating and his respiratory pattern was sporadic and ineffective. I was much more aggresive with the airway than I might have been based just on naked eye observations.

Circling the Drain

Called for difficulty breathing to a nursing home. The woman is in her 80’s and breathing rapidly and shallowly. They have her on a non-rebreather at 4 lpm. They say they can’t get her SAT above 80. They can’t tell me how long this has been going on, but they seem to think it all started this afternoon. Her lungs are very junky. She looks like she is getting very tired.

We go lights and sirens. I am having trouble getting the ECG leads to stick. I can't get a rythmn, but my concern right now is her breathing. She is declining fast. I get out my intubation kit. Her resps are almost agonal now. I disconnect her nasal cannula ETCO2 monitor and hook the ET capnography filter to end of the ET tube and slip in a thin stylet.

I see her chords and pass the tube. I look at the monitor I have no wave form. I must have missed I think. I pull back a little, and then again go through the chords. I have no wave form, but I am not certain now she is breathing. She in fact is apneic. I grab the ambu bag and give it a squeeze and up pops a wave form. I’m in. I secure the tube and start bagging. Her End tidal is 30, but then it soon drops to 17.

The monitor is still not reading the leads. She looks like she is dead. The end tidal is very low. I reach over and do some compressions. I shout to my partner, but he is already out of the ambulance.

He opens the back door. Standing behind him are the patient’s daughter and another family member. His eyes widen when he sees I am doing CPR. He turns and waves to the crew of an ambulance parked in the lot. With their help we get the patient on a board, slaps some pads on – the patient is asystole -- I can check my lung sounds – equal right and left, nothing in the belly, and get a round of drugs in, one epi and one atropine, and then we are wheeling her in.

***

Here’s the trend summary I printed out after the call, which pretty much tells the story of her declining respirations.

The period of apnea includes my taking her off the end-tidal cannula, attaching an end-tidal ET filter to the tube, and then intubating.

November Log

2006-08-02T02:32:00.000-07:00

Seizure

I was dispatched for a CVA. I found an 80 year old woman at an adult day care center who had what sounded like a seizure/possibly hemoragic CVA. Facial twitching, staring off to one side, but was back to normal now possibly. Her daughter showed up and I asked the daughter to look at the mother and tell me if this was normal. I turned around and the mother was seizing again. Not normal. We quickly loaded her into the back of the ambulance, and I immediately put her on the capnography, and then quickly got an IV line, and got the ativan out. On the capnography it looked like she went apneic for about thirty-firty seconds, enough to set the apnea alarm off, and then I could see she was breathing and her ETCO2 was up to 50-60. Then just before I could give her the ativan, she stopped seizing. I tried to run a trend summary, but the monitor I had didn't have the trend software turned on. I quickly got into the code and turned it on, hoping if she had another seizure I could capture what I had witnessed.

She started seizing again, but I didn't see the apnea. I waited a little bit, and then was feeling this conflict between the clinician and the scientist. I wanted to hold off so I could get a good strip showing apnea, and then hypoventilation, but on the other hand, I did have a job to do. So I gave her the ativan. That stopped most of the shaking except for the facial twitching.

Hyperventilation

I was called for chest pain and found a fifty year old woman screaming she couldn't breath and her chest hurt. Her family denied any medical history. I thought she was hyperventilating. I put her on the capnography.

ETCO2-17 RR-56

I tried to get her to concentrate on the monitor, on bringing up the ETCO2 number and bringing down the RR number. That lasted about ninety seconds and then she was again screaming that she couldn't breathe. I checked her out from head to toe. Everything fine. I asked her husband again if she had any medical problems or took any meds or used to, and he just shook his head. On the way to the hospital,while I was on the phone with the doctor asking for orders for ativan to sedate her, in between screaming episodes she let it slip that she didn't want to go to the "purple pod' which is where the psychs go. That told me all I needed to know. The ativan worked wonders. I gave her 1 mg and then a second when she was still agitated, and that did the trick. She really mellowed out.

Here's her strip on arrival at the hospital.

ETCO2-35 RR-17

But then when the triage nurse told her she had to go to the purple pod, despite the ativan, she went back into having a fit, including tearing the capnography cannula out of her nose. "People will here about this!" she screamed. "I am not happy!"

Nasotracheal Intubation

The morning after writing Capnography and Intubation about using capnography to aid intubation, my first call ended up being an intubation in which I used capnography to help intubate.

The call was for unresponsive patient with severe dsypnea. We found an 80 year old female with a GSC of 4-5 breathing at a rate of 60 with cool extremities. Unable to hear BP. Heart rate on the monitor 130-140. Blood sugar - 213. I attached the capnography filter to the end of the ET tube. Some of our ET tubes come with stylets already in them. I removed the stylet, but could not put it back in because it was to thick, so I used a thinner stylet. I went in, and had a hard time getting the woman's jaw open enough to see the chords. We don't have RSI so there was what we call inadequate relaxation. I could just barely see the chords under the epiglottis, but couldn't get the tube to pass through. Instead of checking by assessing breath sounds, I just looked at the monitor. The ETCO2 would just go straight and I'd know I had gone below the chords. I ended up nasally intubating her, which I probably should have done first, but I like to get a bigger tube in. The nasal tube went in great. I used a 6.0 and watched the wave forms as I fed it. The form went down to nothing, I pulled back and repositioned her head and then advanced the tube again, and felt it go through and had the big wave forms to confirm it.

Her SAT went up to 98% from the 80% and her ETCO2 came up from the mid twenties to low to mid thirties. She opened her eyes by the time we were in the ED.

I'm still waiting to hear what was wrong with her - most likely sepsis.

Hypoventilation not Hyperventilation

We were called for an OD, unconcious, but when we got there we found a 32-year-old extensively tattooed woman standing, looking slightly dazed, saying she was having trouble breathing and just needed an inhaler. I listened to her lungs (in the lower lobes) and they were clear, which I announced to the assembled room of five firefighters, my partner, two cops, and three bystanders. Then with the next breath, she coughed and sounded very rhoncorus to the naked ear. "She doesn't sound clear," one of the bystanders said like I was an idiot. "She's talking fine," I said, "using complete sentences." Then I asked the patient what hospital she wanted to go to. She said she didn't want to go, she just wanted a treatment. I said, we don't do home treatments, if she was having trouble breathing we needed to take her to the hospital. Now in the meantime, I am hearing one of the bystanders explain to my partner that someone had found her unresponsive in the bathroom with blood all over the floor and walls that she either vomited or coughed up. I looked in the bathroom, only to see a woman just finishing cleaning it all up. The patient still just wanted a treament, but with the help of the cops, we insited she go with us. I helped her walk down one flight of narrow stairs down to where we had the strethcer. She wanted to walk to the ambulance -- at the same time she was begging with me to give her a treatment. We had her lay on the stretcher and I set the back up straight. Out in the ambulance, I put her on the pulse ox, and while her fingers were cold -- it was a wet, raw day, the pulse ox read less than 50, and then got up to 70. She was really sort of panicking now, and I listened again to her lungs - this time to the upper lobes and oh, my -- they were coarse and rhonocous and nasty. I put her on the capnography thinking that I would see low numbers, and this is what I had. ETCO2 - 70!

She got more and more panicky as I gave her a treatment by mask and had my partner drive lights and sirens the three blocks to the hospital, where we raced her in. The triage nurse and the other crew waiting in line looked at me maybe like I was crazy as I insisted we cut in front and that my patient was in true distress and not just your typical anxiety attack. I had to explain about the capnography -- why she wasn't hyperventilating and how I though maybe she has aspirated. They sent us down to a priority room, where I got the same looks and had to again explain that this wasn't what it first looked like. The doctor listened to her lungs -- lower lobes -- while a nurse coaxed her to slow her breathing down, and I had to have them listen to the upper lobes and show them they she was in fact hypoventiliating.

It didn't take them long to understand and see she was hypoxic. She then coughed up some blood and then admitted she had done two bags of heroin. I will try to check back to find out the final story, but the respiratory therapist agreed he thought she probably had aspirated.

The bottom line for me was while I was at first poo-pooing her complaint -- she appeared after all the typical junkie whiny borderline asthmatic anxiety type with a chest cold, the capnography slapped me in the face to what maybe I should have been seeing all along. It screamed out -- she is having a big problem!

I gave her a treament, which didn't seem to help her too much, although her ETCO2 number did come down into the high 50s. Her respiratory rate also picked up, which may have driven the number down some.

Just why the number was elevated, there are a number of possibilities. She had possibly been apneic before being found, her tachycardia -- 136 -- increased cardiac output drove the C02 number up, the aspiration tired her and limited air movement.

I'll update if I get any more information.

Respiratory Distress

I intubated an 80 year old woman in a nursing home who was breathing agonally (gasping like a fish) and had no palpable pulse or ausculable BP. Of course the nursing home had her on a mask at 4 lpm, and when I told the nurse to take her off it and start bagging her -- at least they had an ambu-bag out, she put the ambu bag on her like it was a face mask and just left it there. No, you have to squeeze the bag! I said. The patient was very cool and clammy.

I first put on the capnography cannula while my partner stepped in and started bagging her. Her ETCO2 was 24. I intubated her easily, and, as always, was glad to see the wave forms on the monitor.

Note: The bumps in the 2nd and 3rd wave forms are her efforts to breathe. The arrows at the bottom are indications of her pacemaker firing.

While I still couldn't get a pulse or BP, I knew from the ETCO2, she at least had some cardiac output. She stayed about the same all the way to the hospital. I couldn't get an IV in, so I didn't do much more than assist her breathing. At the hospital, she finally opened her eyes.

I kept her on our capnography until the hospital could find theirs. They just got one, and all it records is the capnometer, not the wave form.

I know the AHA recommends that you do all the checks to make certain, your ET tube is in, but with capnography, I tend to skip certain checks such as using the bulb syringe, and I may delay the lung sounds. If I see the tube pass, I have a wave form, and I have mist in the tube, with a breathing patient, I don't really think the bulb syringe is neccessary. In a potentially fast moving scene, such as an imminent arrest(which this looked like at first, but turned out not to be)maybe the capnography is good enough.

In this call I didn't check the lungs and belly for several minutes. At the hospital we are required to have the ED doctor verify our tube by listening to the lungs and belly. I wasn't concerned because I have the capnography going right there, and the trend summary showing a constant ETCO2. She checked them and signed the sheet for me.

Postscript: Thinking about this later, you still need to check lung sounds to make certain you haven't intubated the right mainstem.

Stroke patient

70 year old male with left sided weakness, nonverbal, gazing to the left. His ETCO2 started out at 23 and slowly went down to 17. I couldn't really figure it out. He was tackycardiac, and his pressure was 110/50. His respiratory rate increased slightly from 20 to 24. I don't know whether the low ETCO2 was due to a poor reading, hyperventilation, or declining cardiac output or saliva on the mouth part of the capnography line. I am going to try to follow up to see what happened to him in the ED after we left. Many capnography stories are picture clear, others like this one leave me puzzled.

?Pneumonia/CHF

Had a 65 year-old female with increasing shortness of breath on exertion. Some CHF history. Pedal edema. Her lung sounds were decreased in the lower left lobe. She appeared in no distress sitting, but quickly became short of breath on standing and pivoting into our stair chair. Big heavy woman. Three floor carry-down. (Whine Whine). Her vitals were fine. Sat 97% on a couple liters. I eye-balled her respiratory rate at 20. I wasn't going to put her on the capnography. I'm trying to only use it now when I really need it as opposed just general experimentation -- I don't want to depelete our supply. Then just as we neared the hospital, I eyed her a little more closely and she did seem to be slightly short of breath, although she denied it. I put her on the capnography and got the strip below.

I was startled to see her respiratory rate was 40, and stayed there. Her ETCO2 was low due to the hyperventilation. I guess it just goes to show, you can't eye-ball a respiratory rate and expect to be accurate. At the triage desk, I waited for the triage nurse to eyeball the respiratory rate. She wrote down 24. I then told her I was getting 40. Whether or not, that higher rate made a difference in the order of care she got in the crowded ED, I don't know, but maybe.

For those who missed it, here's the classic waiting room computer shot that appeared in the Annals of Emergency Medicine about synpnea -- where everyone in the waiting room gravitates toward the same respiratoty rate:

Vomiting COPDer

Called for dsypnea. Found an 80 year old female with a respiratory rate of 34, a fever of 101, and ETCO2 of 34, and an upright capnograph. Her lungs were decreased. No wheezing. I upped her 02 from 2 to 4 on the capnography dual cannula to get her SAT from 89 to 94. The only problem with the capnography cannula was she vomitted, and splashed the mouth flap, so I had to clean it, and then everytime, she puked, I had to move it out of the way, basically taking her off 02.

Unresponsive

We get called to a nursing home for an unresponsive patient. A 55 year old male IDDM with a big psych history, who was recently discharged from psych hospital on heavy duty meds. His blood sugar is 220. Pupils midsized. BP 120/70, HR - 84. Skin warm and dry. Does not respond to sternal rub. Does not respond to IV. Only semi-response we get is from moving him from bed to stretcher on draw sheet.

Capnography shows ETCO2 is 35. RR is 12.

Monitor him all the way in. Capnography and RR remains constant.

My guess is he is over medicated. At the hospital they ask if we gave narcan. I say no because his respirations are 12, his pupils non-constricted and the capnography shows he is ventilating noramally.

I like the use of capnography here just to get a quick picture off the back whether he is having a problem or not. Someone else might try to intubate him due to his GCS in the 7-9 region. For me the capnography shows no ventilation problem, his airway appears patent. We just monitored him on the way in.

Infant

We got called or an infant, whose mother said he had stopped breathing for about two minutes, and just wasn't right. The two week old seemed okay to me. Out of curiousity, I tried to put a capnography cannula on him, but he was too little. No matter how I positioned it, I couldn't get a reading.

To read other month logs, click below or on side bar:

October Log

2006-08-01T01:30:00.000-07:00

Presumption - Hiccup

I did a presumption involving a fresh death and questionable DNR detailed in the story Understand. I had never used capnography before on a presumption, but ever the field scientist, tried it(putting a capnography cannula on the patient): 1) to document the apnea, 2)to give myself some time to think of what I was going to say about the unusual circumstances surrounding the case when I called in for permission to not begin CPR, and 3) out of pure curiousity. I immediately saw the flat line of apnea, but then a few minutes later was startled by the appearence of the number 7 in the capnometer without a wave form. I figured later that the 7 probably came from a stomach hiccup or some type of passive gas escape. Here's the trend summary.

Note: the slight bumps in HR are due to the patient's pacemaker.

I don't know if it is necessary to document apnea in a presumption. All we are currently required to do is run a six second strip of asystole in three leads, but in any sort of nonstandard presumption(perhaps traumatic arrest patients), I don't think it could hurt to have a trend summary of RR, ETCO2, and HR. The future is going toward not transporting traumatic arrests in most cases. In light of the occasional story of a patient waking up later, the trend summary might be good documentation and use less paper than a minute plus long strip of asystole.

I would also use this on freshly desceased DNRs.

COPD - Hypoxic drive

Called for a man with lung cancer and COPD. He was satting in the low 80's on his home 02 with slight wheezing. We put him on a nonrebreather when his sats didn't improve with a few more liters by cannula. While his SAT went up to 100%, his end tidal also went from 37 up to 52, and his respirations dropped slightly. The point of all this is for all the debate about the hypoxic drive and not giving COPDers too much 02, if you are at a nursing home or a doctor's office and they tell you not to give over 2 liters while you are putting a mask, you can just say, not to worry, you are monitoring the patient's ventilations with capnography.

Here's the trend summary (HR, SP02, ETC02, RR):

Initial capnograph:

On nonrebreather:

"Quick Look"

When I have a patient who looks sick, but I am not certain how sick, I like to put the capnography on right away and that can either relax me if the numbers and wave form are good or kick me into high gear if they are bad. Bob Page put it very well in his class calling this "The Quick Look of Life" or as he titled his lecture, "Slap the Cap!"

Here's two patients who I encountered in back to back calls the other day.

1. 39 year old female in third floor walkup, lying across bed in cockroach infested apartment. Complaining of chest pain, breathing rapidly. Skinny emaciated with distended abdomen, diaylsis port and a pacemaker. History of asthma. Lungs clear above, slight crackles in bases. Hasn't been to diaylsis for a week.

RR- 62 ETCO2 - 22

"Stair chair," I said to my partner.

At the hospital they weighed intubation, but ended up giving her emergency dialysis. Her PH was 7.3

2. 80 year old patient altered mental status, altered breathing, possible aspiration. You can hear the rhonci from the doorway. DNR, supportive care only. Staff at Nursing home says patient's pulse - 112, BP 160/100.

Here's the quick look.

RR - 32 ETCO2 -14

We couldn't feel a pulse or get a BP.

Here's his ECG:

Certainly helps illustrate the case for ETCO2 as a measure of cardiac output.

At the hospital his PH was 7.1. They called his doctor and family to see how aggressive they wanted him treated, and ended up trying to pace him, which didn't work until after they gave him calcium. It seems he was extremely hyperkalemic. I would have liked to have seen what his ETCO2 did when they finally got a pressure. When we saw him an hour later he was still puffing away, trying to blow off CO2.

September Log

2006-08-01T01:17:00.000-07:00

Capnography Lectures

Here’s some of my notes from the lectures. The notes don’t reflect the entirety of the lectures, they are just my notes on ideas that were expressed in an interesting or thoughtful way. While most of the material was familiar to me, and both lectures covered identical ground, some of it was said in a way that shed more light on the subject.

Bob Page Notes

1. Capnography is the “quick look of the living.” You put the pads on a person in arrest to get a quick look at their rhythm. You put capnography on a living person to get a quick look at their ABCs. If they have a good capnography number, you know they have a patent airway, are breathing, and circulating.

2. Hypocapnia/Hypercapnia versus Hypoventilation/Hyperventilation. Page used the first breakdown as his description for high and low capnometers respectively. I agree with him it is a better breakdown. Hyperventilation has too many connotations of someone breathing rapidly.

3. Respiratory Rate versus ETCO2. To see if a person is hypoventilating, the ETCO2 is much more accurate than the RR. The RR is just a measure of how many times someone is breathing. The ETCO2 is how they are ventilating. A person breathing at 6 a minute may be ventilating perfectly well and not need bagging versus someone who is not ventilating well.

4. Numbers of capnographs – While I have used his quote in the past -- “End Tidal CO2 reading without a waveform is like a heart rate without an ECG recording.” – he pointed out that there are really only five capnographs – normal, high, low, obstructed and rebreathing.

5. Seizures – If someone is having a grand mal seizure, the medulla oblongata that controls breathing is knocked out, and the capnography will show no breathing. Capnography can also show the duration of the seizure if you hit print once a seizure starts.

6. An Upgrade – Capnography is an upgrade for EMS. In terms of monitoring, we go from detection to diagnostic, static to dynamic, reactive to proactive, subjective to objective in terms of what the data can do for us.

Page teaches class called “Slap the Cap.” He is on the schedule to teach at EMS Today in Baltimore next March.

Baruch Krauss Notes

1. Unconscious obtunded Patients – Capnography gives you a great look at whether you have an immediate problem. For instance, Is your patient drunk or are they drunk and hypoventilating?

2. ETCO2 Trending -- a few minutes of ETCO2 readings can give you a good idea of which direction your patient is headed.

3. DKA – Diabetics over 36 are not in DKA because they cannot be acidotic, diabetics under 29 may well be in DKA.

4. Hyperventilation and Hypoventilation are not just determined by respiratory rate, but respiratory rate plus tidal volume.

5. Traditional Means of Verifying an ET Tube are unreliable. There is condensation in 20% of esophageal tubes, 16% of the time OR anesthesiologists mishear lungs sounds. Esophageal intubation can also produce chest wall rise.

6. Stress Reducer – Capnography is a great stress reducer by informing clinical judgment reducer. You know right away whether you have a big problem or not. Whether you have your tube, whether your patient is hypoventilating, etc.

7. The PEA or Not Question – I got to ask Krauss my favorite capnography question and he said if you have a significant ETCO2 number and you aren’t doing compressions, then you have cardiac output.

8. In the ED -- Krauss gave a good suggestion on how to "spoonfeed" the ED your capnography data, you say something like ...The patient was oxygenating at ...whatever pulse ox says... but I was worried about his ventilation, so I put him on the capnography and his ETCO2 shows....

Cannula Positioning

The positioning above produced the following wave form:

Due to the patient's mouth breathing, the cannula was then repositioned.

And the new wave form:

Thanks to bdmedic for submitting.

Pneumonia/CHF

We took in a fifty-year old nursing home patient with a pneumonia/CHF, IDDM, PAD history. He was alert and orientedextremely tachypnic with a rate of 44, lungs were rhoncorus, he had some pedal edema, but showed no difference in breathing whether he was laying flat as we found him, or sitting him up as we did. He had a fever of about 100. His wave forms were upright and his ETCO2 fairly constant at 35. He had no IV access so we didn't do anything for him, but give him supplemental 02 at 4 lpm. His Sat was 100%.

At the hospital the x-ray showed pneumonia, and maybe some CHF. His arterial CO2 was 37. I have been trying to check when I can to compare the arterial PaCO2 with our PetCO2, and so far in every case it has been very close.

I'll post the strip later.

Capnography to Monitor Respiratory Rate

I was reviewing the slide show on Capnography put together by Reuben Strayer, an M.D. at McGill, and was facinated about his comments on respiratory rates. We all take fairly religous blood pressures and pulses, with maybe only an occasional "seer pressure." But respiratory rates tend to be another thing. I admit to often eye-balling the rate. Now that I am using capnography, which provides the true rate I am surprised that I have often over-estimated the rate. Strayer cites a number of papers on respiratory rate, including one from the 1950's when an audit of a VA hospital found that 94% of all recorded respiratory rates were between 18 and 22. The norm is 14-18. Their conclusion was that RR should be elimiated from patient records saving 3.5 million hours of labor a year nationwide and thus saving taxpayers $5.5 million dollars. The average nursing wage was $1.50 an hour then. He then cites a paper from the 1980's that shows that respiratory rates "if carefully measured, are a sensitive and reasonably specific marker of acute respiratory disfunction." Another study found that "independent measures of respiratory rate may differ by more than 35%, which implies a measured rate of 16 breaths/min may actually represent a rate anywhere between 10 and 22 breaths/min."

The best paper, he cited was from the Annals of Emergency Medicine, which showed a screen shot of a computer listing vital signs of patients in the waiting room of an ED. All the RRs are 14. This is a quote from the paper. "The figure displays an under-recognized clinical phenomenon for which we are proposing the term 'synypnea.' Synnypnea is seen across the country and is defined as when all emergency department witing room patients have the same respiratory rate. We think it is pathophysiologically linked to menstral synchrony. There is little scientific exploration on this topic, however, which represents fertile grounds for original research."

Hyperventilation

We had a patient today. Woman in her fourties with chest pain and dizziness. Under a lot of stress. Her EKG was noraml. We put her on the capnography and she was breathing at 30 times a minute with an ETCO2 of 24. She was really dizzy she said. We worked her up for a cardiac, but we also treated her for hyperventilation. We had her stare at the monitor and coached her to try to lower the respiratory rate and raise the ETCO2. It worked okay. She was able to get her respiratory rate down to 20 and her ETCO2 up to 31.

Later, I had my preceptee put on the ETCO2 cannula and try to hypoventilate himself, and then hyperventilate himself. He got his ETCO2 up as high as 52 and then down as low as 26. He said when he was hyperventilating, he felt really really dizzy and it helped him understand why she had such a hard time when we had her try to walk a short distance to the stretcher.

August Capnography Log

2006-07-31T07:07:00.000-07:00

ROSC / ? Hypercapnic Arrest

The call is descibed in my Streetwatch blog under the story The Line.

Basically it is about an asystolic arrest. I arrived as the second unit, 10 minutes after the first unit arrived, and probably at least ten minutes after the patient went down. He was found by a neighbor who entered his apartment and found him on the floor, not breathing and called 911. He was asystole for the arriving medic and still asystole on my arrival. His airway was full of secretions. After I got the tube, I was startled to see an ETCO2 of 52!. After three epis and two atropines, we got pulses and BP back and his ETCO2 went up to 101, before coming back down to the 50 range. I found out at the hospital he had a history of hypercapnia, which helps explain the high ETCO2. It certainly was a case that despite everything suggesting we weren't going to get him back, that the higher the initial ETCO2 the better chance to rescusitate the patient.

Here is a strip and the trend summary:

Two Cannulas No Good

I grabbed two capnography cannulas from the storeroom today and tossed them in the bag without looking at them. We were called for a diabetic and found an 79 year old female quite anxious stating that her blood sugar was over 400 and she felt very dizzy and had a headache. I tossed her on the capnography and got a reading around 35 with a good wave form everything quite normal. I asked my partner to attach the oxygen tubing to hook it up to the cannula port on the capnography cannula, but then we realized this batch of cannulas lacked an 02 extension, so we had to put an 02 cannula on the woman in addition to the capnography cannula. I noticed her ETCO2 started to go down and I at first thought it was because she was hyperventilating. It went all the way down to 17. And then I thought maybe the oxygen cannula has something to do with it. The moment I took the oxygen cannula off, her ETCO2 went right back up to 35. The oxygen cannula was obviously diluting the carbon dioxide sample. Here's the trend summary that shows the dip:

Moral of the story: You need to use the cannulas with the separate 02 ports, especially for nose breathers.

As far as the patient, her glucometer had given her an inaccurate reading. Our glucometer showed 160. The hospital 122. The dizziness and headache all began after she started worrying about her high blood sugar.

Cardiac Arrest - /?Seizure

On the way into work I heard over the radio the night crew getting toned out for a patient who is cold according to his mother. It was updated as CPR in progress. I responded right to the scene to assist. It was a 40 year-old male
in asystole, cool with no apparent rigor or lividity. The other medic was going for an IV so I went for the tube. There was a slight bit of rigor in the jaw -- it wasn't flaccid, but I could open it and , but I was able to get the tube in. His mother was in the room, and due to his age the other medic had made the decision to keep working him. I couldn't find the capnography circuit. I had to go out to the truck to look for another one, couldn't find one, and then came back inside and found one buried in the ET kit. In my gear I have the circuit right there as soon as I open my kit. Here's the wave form:

The initial end tidal was 9. During the course of working him it went as low as 6, but never got above 10. At one point the apnea alarm went off. I couldn't figure out why it was going off, and then I looked I saw that the person bagging had the ambu-bag off to the right, instead of up straight, and the tube kinked off near the top of the mouth holder so it could bend to the right. We corrected that and carried on.

The other medic called the hospital for permission to stop after twenty minutes and it was given. The research shows after 20 minutes with the CO2 less than 10, there is no chance of survival.

As we cleaned up, the mother knelt by her son's cold side and threw her arms around him.

Anxiety/Seizure

We were called for a seizure. A forty-eight year old seminude sunbather with an ETOH/psych/seizure/NIDDM history. Supposedly hadn't had a drink for three years, but had put vodka in her lemonade today and maybe in previous days. She was thrashing around when we got there, very hot and diaphoretic. Her intial ETCO2 was 38 with a good wave form. Her blood sugar was fine. We ended up giving her some Ativan just to calm her down. I don't think her seizures were real. It was interesting that on the capnography when she had the seizures, which never lasted more than 30 seconds, she was apneic. Perhaps holding her breath. She had no postictal period. And was able to converse in between. I'm going to try to get the capnography on all my seizure or faking seizure patients and see what I can learn.

Research

Spent part of the day at the University Health center Library, which is great. They have access to a ton of research articles that their high speed printer spits out for you in no time. I will be reading the articles I got and posting about the ones I can make sense of. I have to admit some of the stuff is really really technical and I feel my own understanding of physiology is shamefully inadequate. There was one article about the relationship of ETCO2 and cardiac output and cerbral perfusion that makes me feel like a kindergardener trying to read James Joyce in Greek.

Hypercapnia

COPD/CHF/Pneumonia history with dsypnea increasing since yesterday. Obese male. Lungs have expiratory wheezes, difficult to say if there are rales. Appears tired, but not diaphoretic. Respiratory rate isn't too bad in the 20's. Uncertain how mentally sharp patient is normally. Has some mental retardation so it is also hard to say if he is a little obtunded. Probably not, but maybe. SAT is in the high 70's on room air. Nonrebreather gets it up to 95%. We give him a combivent treatment.

Here is his capnography wave form:

His initial capnometer is 72!

Here is his trend summary.

Note: the pulse oximeter was off for a good part of the call because the chord was too short.

With 02 his SAT goes up to 95%, His ETCO2 goes down to 57. At the hospital a nurse looks up his last admission for us. He came in with an PaCO2 of 88 that was corrected down to 75. This guy then has a history of hypercarbia -- too much carbon dioxide in the blood. While giving someone with hypercarbia supplemental oxygen can make them worse, clearly in this case it made him better, and in no case obviously should you ever withhold oxygen from someone who is hypoxic.

Asthma

Okay this one confused me. 19 year old girl history of asthma with hospitalizations, but no intubation with increased dsypna unrelieved by inhaler. When we got there she was on a nonrebreather by the first responders, her lungs were decreased, and she was doing some slow labored breathing. Her capnometer was 40. Hereis her wave form, which didn't look to bad.

I give her a treatment through a mask. She says she is breathing better. I now hear inspiratory and expiratory wheezes. She is breathing deeply and slowly. Her hands grip the stretcher. Then her capnography drops down into the teens with this as a wave form:

Here's the trend summary.

En route she gets two treatments and in between is on a non-rebreather.

The odd thing is while her ETCO2 is going down, so are her respirations. She looks about the same. I don't know if my machine is malfunctioning or if she is really undergoing a change for the worse. Maybe she is hyperventilating, not by breathing too fast, but by taking too deep breaths in trying to get air. At the hospital they give her four more treatments and solumedrol and she goes home that night.

Bad Reading

A little bit of a setback for capnography today. I had a 33-year old female with severe vaginal bleeding(an evident miscarriage. She was alert. Her pulse was 112, her BP was 130/90, her sat was 100%, she was warm and dry, but dizzy on standing. I was getting capnography readings in the high teens, and then the apnea alarm would go off when she was still breathing. I tried another capnography cannula and I was getting the same problems. Only occasionaly would I get a good reading, and then it would wander off mark and the apnea alarm would go off. I'm guessing it had something to do with the way she was breathing and maybe the cannula just not sampling the air right. Her mouth was closed, and maybe she had some wierd curvature of exhalation. I may try to replicate odd breathing to see if I can make the machine show apnea when I am still alert, stable and breathing.

Experiment

Only 1 call in eight hours today so I spent the day redesigning the site and revising the "10 Things" document. I conducted an experiment where I hooked myself up to the monitor, pulse ox and capnography, and then tried to hypoventilate, which is hard. I almost passed out. Here are the results:

You can see the respiratory rate going down steadily (from about 12 down to zero) while the ETCO2 rises steadily(from 35 up to almost 50), and then there is the period of apnea. All the while the SPO2 stays around 98%, and the heart rate slowly goes up(from 70 to 88), then starts to brady, then shoots up (to almost 90) during the thirty-plus seconds of apnea, then drops when I finally start to breathe again.

I think I will try to replicate this with supplemental oxygen, and may also try to recruit some volunteers.

MS for Hip Fracture and a COPDer

I had an 80 year old woman with a broken hip in extreme pain. She had taken one tramadol, which obviously hadn't touched her. I like to premedicate the patient before I even try to move them so, in increments, I gave her 7mg of Morphine over ten minutes. I waited about five minutes more, and then we packaged her on a scoop stretcher. Out in the ambulance she was still in a fair amount of pain and the roads we were on were pretty bumpy so I called to get permission to give her 3 more mg, and I was pleased the doctor actually told me to go ahead and give her 5 more mg. (We can give up to 0.1 mg/kg on standing order, and have to call for more.)

The extra morphine worked wonders. I had her on capnography to monitor her respirations/ventilation. By the time we got to triage, while she was still awake, she was feeling no pain and her respirations, which had been in the high twenties were down to 8. Her ETCO2 remained constant.

Here's the wave form strip:

Here's the trend summary for ETCO2 and RR.

Later we did a COPDer -- a real pursed lips breather. He is a frequent flier and his complaint today was fever, the runs, headache, chest pain, dsypnea. I was convinced he had pneumonia, which is what he always had. His lungs were decreased and he had some expiratory wheezes -- again his normal. While I gave him one treatment, he said it didn't make him feel any better and he kept the shark fin wave form, which I expect he will never be able to get rid of at this point in his disease.

Apnea

2006-07-02T11:34:00.000-07:00

Capnography to Monitor for Apnea:

We intercepted with a basic unit for a possible cardiac arrest. It turned out to be a patient with end-stage cancer who was a DNR, but the family didn't have the paperwork. She had become unresponsive and they thought she had stopped breathing.

When I climbed in their ambulance she was breathing, but responsive only to pain. The crew said her BP was 80/50. I put her on the monitor to see a sinus rythmn and put her on capnography.

While I was going for an IV line, the apnea alarm went off.

I gave a sternal rub and she started breathing again.

Here's a strip of her declining respirations:

She had several episodes of apnea, but now by watching her we were able to keep her aroused enough to get her to the hospital without having to do any advanced airways or to bag her. There they were able to contact her doctor and affirm she was a DNR.

Here's the trend summary:

Welcome

2006-05-07T11:20:00.000-07:00

May 2006

Hi, everyone.

I am using this blog to explore the issue of capnography in the prehospital setting. Unlike with 12-Lead ECGs, you can't just go out and buy a book. The information on capnography is out there, but not that accessible. I want to use this site to gather that information into one place, as well as to post my own experiences.

I first heard about capnography at the JEMS conference in Philadelphia a few years ago. I took a one hour mini-class from a vendor. In one ear and out the other. I didn’t have capnography so it didn’t stick. Last year, we finally got capnography put on our Life Pack 12s. I learned how to put it on the ET tube, but the first couple codes I did, I completely forgot that I had it, then the next couple times I remembered about ten minutes into the code. Now, I keep an ET filter line in my airway kit, so it is starring at me when I unzip the kit.

The first code I used the End Tidal Monitoring on, I was alarmed that I didn’t get much of a wave form and that my capnography number was so low. (See Compressions). Later I did a call where the patient initailly looked so dead, I thought she was going to have rigor when I touched her, I popped the filter line on and was startled, after a few minutes of CPR, to suddenly see an End Tidal number of 35 (See A Blanket). A short time we got pulses back and then later the patient began breathing on her own. I have learned that capnography can be a predictor of rescuitation chances.

Most of all a good capnography wave insures that the tube is in the trachea where its supposed to be and not in the esophagus which would produce a flat line, immediately on the capnography wave form and eventually on the heart monitor as well if the tube is not moved to the right place.

In April 2006 I took a really good class on capnography, taught by Gary Childs of the Mercy Hospital Education Center.

Part of the class covered capnography for the non-intubated patient, which was the main reason I took the class. Instead of an attachment on an ET tube, a nasal cannula-like monitoring device was put on the patient. We were taught that the shape of the wave form changed depending on the problem. Asthmatics and COPDers had a characteristic shark fin shape, which indicated resistance to expiration.

I am hooked on using capnography now, and every time I use it, it seems I learn something new.

Here is the outline I am going to try to use for this blog

1. What's New?

A dated list of all new additions to the blog in recent days.

2. 10 Things Every Paramedic Should Know About Capnography

This is a document in-progress. I may at some point do a companion piece -- Another Ten Things Every Paramedic Should Know About Capnography, but that will have to wait until I learn another Ten Things.

3. Capnography News

The latest on capnography

4. Web Resources

The best capnography links on the web -- that I know about anyway.

5. Clinical Studies

I will try to summarize or at least list the Abstracts of the best studies on capnography in EMS.

6. Capnography: Clinical Issues: Text Book

I will provide my notes from the only up-to-date Capnography textbook currently available.

7. Case Studies

These will be interesting cases I have had.

8. Monthly Capnography Logs

A record on my daily use of capnography and what I am learning. I will archive this section every month.

Because I am still a novice at it, I don't claim that my interpretations will be 100% accurate. If I am wrong or off-base or you can add something to my understanding, please feel free to comment. Also, any links to other capnography sites would be appreciated.

Thanks,

PC

Capnography News

2006-05-06T10:07:00.000-07:00

I intend to use this heading to list any breaking news about capnography.

February 22, 2007 - JEMS Report Capnography Nationwide

According to the February 2007 JEMS 200 City Survey, capnography use in intubated patients increased from 76% in 2003 to 94.8% of the cities in 2006. The article does not mention whether or not the cities are using continous wave-form capnography or colorimetric.

February 4, 2007- Capnography Grant

I found on the internet an application for a large research grant for EMS Capnography.

EMS Capnography Grant

Here's an excerpt:

PURPOSE OF THE CAPNOGRAPHY CAREER DEVELOPMENT AWARD
Capnography is the non-invasive measurement of the partial pressure of carbon dioxide in exhaled breath expressed as an end-tidal CO2 number and a waveform in adults, children, infants, and neonates. CO2 can be sampled from the patient’s mouth or nostrils. Although standard of care in anesthesia practice, the use of capnography in emergency medicine has primarily been limited to intubated patients for verification of endotracheal tube placement and for cardiac arrest. There has been little emphasis on the use of capnography for assessing ventilatory, perfusion, or metabolic status in spontaneously breathing patients. Carbon dioxide measured at the airway can be displayed as a function of time or exhaled tidal volume. This award is specifically for human clinical research on time-based capnography in spontaneously breathing patients and is especially interested in new clinical applications for use of capnography in non-intubated patients. Specific examples of eligible projects would include but not be limited to:

· Capnography to determine ventilatory status in non-intubated infants and children undergoing lumbar puncture

· Capnography in patients with known lung disease to predict the arterial partial pressure of CO2 using nonlinear computational methods, e.g., genetic algorithms, artificial intelligence

· Capnography in patients receiving procedural sedation as a surrogate measurement of minute ventilation

· Prognostic significance of a single measurement of CO2 as a predictor of in-hospital complications in patients with known heart and lung disease

· Utility of capnography as an effort-independent mechanism to assess severity of obstructive lung disease

· Diagnostic accuracy of exhaled CO2 to detect and risk-stratify acute pulmonary embolism

· Accuracy of capnography as a measurement of respiratory rate in triage

· Capnography as an early indicator of mechanical pacer capture

· Capnography as a measure of the effectiveness of fluid resuscitation in hemorrhagic shock

· Relationship between blood pressure and EtCO2 in early cardiogenic shock

· Accuracy of EtCO2 as a measure of cardiac output in patients with tachyarrhymias

· Relationship between EtCO2 and carboxyhemoglobin in carbon monoxide poisoning

· Utility of EtCO2 to distinguish methanol or propylene glycol from isopropyl poisoning

These scenarios are offered only to provide a conceptual basis as to the scope of the award and include ventilation, perfusion, and metabolism applications of capnography. Projects that would be considered nonresponsive would include use of vertebrate animals, post-operative patients, or intubated patients in the emergency department.

May 29, 2006 -- The Use of Capnography as a Guide for Oral Intubation

I just read about a study, which may have just concluded in New Jersey. No results have been published yet to my knowledge. Here's the purpose:

"The purpose of this study is to assess if capnography can be utilized to assist in the process of endotracheal intubation. Specifically, in locating the glottic opening. Ultimately this would result in a new use of capnography to aid in securing normal and difficult airways. Currently capnography is only utilized for the confirmation of endotracheal tube placement.

If successful, this study will provide information, and allow for the development of instrumentation, that will assist in difficult airway management. Specifically in locating the glottic opening when visualization may be impaired. Ultimately, this technique will be useful for routine and emergency airway management."

The Use of Capnography as a Guide for Oral Intubation

I also came across this new study using a technique called fibrecapnic intubation. It sounds like they use the device to capture capnography wave forms (perhaps much like we listen for breathing when nasally intubating)to gain proper positioning. They also visualize the tracheal rings. For more click:

Awake fibrecapnic intubation: a novel technique for intubation in head and neck cancer patients with a difficult airway.

Capnography and Terrorism

Capnography as a rapid assessment and triage tool for chemical terrorism.

In an article the August 2005 Emergency Pediatric Care, Baruch Krauss proposes the use of capnography as "a prehospital assessment and triage tool for monitoring victims of chemical terrorism and for critically ill patients" because "Capnography provides the ABGs in less than 15 seconds and identifies the common complications of chemical terrorism."

Here's an easy to read article from the June JEMS on the same topic:

15 Second Triage Tool: The use of capnography for the rapid assessment & triage of critically injured patients & victims of chemical terrorism

Capnography: Clinical Issues (Textbook)

2006-04-01T01:46:00.000-08:00

I recently bought this book, which as far as I can tell is the only close to up-to-date Capnography text book available.

While the book is it not directed at EMS, it does have some chapters dealing with prehospital use of capnography. I will be slowly making my way through the book and will try to notate some of the hightlights below:

***

Chapter One – Clinical Perspectives

Emphasizes that a capnogram is a “snapshot in time,” a brief episode in a phase of a patient’s disease.” Every change will induce other changes as the body tries to maintain homeostasis. Capnography can only tell part of the story.

Capnography represents pulmonary perfusion so a drop in cardiac output will be reflected in a drop in pulmonary perfusion and thus show up as evidence captured by capnography.

Intubation of right mainstem bronchus will produce lower C02 values because only one lung is being perfused.

Chapter Two – Capnography and Respiratory Assessment outside of the Operating Room

We evaluate respiratory status by watching chest rise, respirations, use of accessory muscles and listening to breath sounds. The problem is the patient the patient needs to cooperate.

Capnography provides continuous readings, regardless of patient cooperation.

While the ultimate test of ventilation is the arterial blood gas, it is an invasive procedure that provides only a momentary value.

End tidal CO2 is an established standard of care for patient monitoring, according to the American Society of Anesthesiologists.

The American Heart Association considers capnography the standard of care for determining ET position.

Colorimetric CO2 indicators are too sensitive to even a low amount of CO2 so they may give false readings.

In stable patients with normal body temperatures, arterial blood gases and end tidal CO2 should be the same.

Capnography is the superior method of measuring respirations or respiratory disruptions compared to visualization or pulse oximetery.

Chapter Three- Airway Management: Prehospital Setting

Unrecognized misplaced intubations (UMI) have occurred at an alarming rate in the prehospital environment. 2/3 of misplaced tubes are in the esopagus, one third in the hypopharanx.

Pulse oximetry may take a few minutes to detect desaturation, especially when the patient has been preoxygenated. End tidal CO2 can detect problem immediately so action can be taken before the patient becomes hypoxemic.

The EDD (esophageal detector device) is unreliable in patients with morbid obesity, pulmonary edema, or ET obstruction by blood or vomit. The EDD does not provide continuous airway confirmation. It is also contraindicated in children under five and pregnant patients.

When patients in arrest have a return of spontaneous circulation, it causes an instantaneous increase in ETCO2, prompting rescuers to stop CPR.

If a wave form is present, the tube is correct.

While ingestion of carbonated beverages may briefly produce ETCO2 readings, the wave form is vastly different from a normal waveform and the ETCO2 falls rapidly to zero.

In a study by Silvestri (see Clinical Studies) continuous monitoring reduced UMI to 0 from 9% for colorimetric and 25% from no capnography.

Chapter Four: Airway Management in the Intensive Care Setting

Endobroncial intubation is a major cause of desaturation.

Capnography can be used to place enteric tubes.

Chapter Five – Airway Management in the Operating Room

Head and neck movement can move an ET tube 5 cm. Problem is worse in infants.

Capnography can be used for blind nasal intubation.

Capnography works with the LMA in spontaneously breathing patients.

Chapter Seven: Monitoring During Mechanical Ventilation

Changes in the metabolic rate change CO2 elimination.

Increased metabolism can be caused by fever, sepsis, pain and seizures.
Decreased metabolism can be caused by hypothermia and sedation.

ETCO2 changes should alert caregiver to changes in the cardiovascular system.

Hypovolemia will cause a decrease in ETCO2

Pulse oximetry provides inadequate monitoring of patient’s respiratory status when the patient is receiving oxygenation.

Increasing ETCO2 may indicate muscle fatigue and need to assist ventilations.

Chapter Eight: Capnography in Transport

Respiratory change is common during transport.

Capnography can be used to place a nasal ET tube. The ETCO2 will increase as the tube approaches the chords and decrease if it starts going down the esophagus.

A number of patients with PEA may actually have cardiac activity. Capnography can distinguish between PEA and low cardiac output states.

Because ETCO2 measures cardiac output, rescuer fatigue during CPR will show up as decreasing ETCO2.

Cardiac arrest survivors had an average ETCO2 of 18 20 minutes into an arrest, non survivors averaged 6. In another study, survivors averaged 19, and non-survivors 5.

But survivors with a low initial ETCO2 are not uncommon.

Bicarb causes a temporary <2 minute rise in ETCO2, high-dose epi can cause a decrease.

High 02 concentrations can lower ETCO2 by 10%.

Chapter Nine: Capnography as a Guide to Ventilation in the Field

Head Injured Patients

End tidal C02 is very useful in monitoring intubated head injured patients. The chapter discusses the problem of prehospital hyperventilation due to the excitement of the situation (which often leads medics to unknowingly over ventilate). Since hyperventilation leads to hypocapnia, which can exacerbate cerebral ischemia, the chapter recommends a target end tidal C02 value of 35. It discusses permissive hypercapnia which may lead to increased cerebral perfusion and improved outcomes. It also says ischemia can occur quite quickly and the brain is very vulnerable right after it has sustained injury.

Chapter Twelve: Capnography During Sedation

Ventilatory depression is common during sedation and often is a greater risk to the patient than the procedure being performed.

While some have advocated withholding supplemental oxygen during sedation to enable a pulse oximeter to more quickly identify hypoventilation, it makes more sense to provide oxygen and monitor for hypoventilation with capnography.

The American Dental Association uses capnography as its standard of care for patients undergoing deep sedation.

The following can, in some cases, hinder accurate readings of ETCO2: secretions, partial obstruction, low tidal volumes, rapid breathing, large diameter of nasal prongs, mouth breathing, dilution by supplemntal oxygen.

Chapter Fifteen - Therapeutic Use of Ambulatory Capnography

Respiratory Training with Capnography can raise a patient's ETCO2 and reduce their vulnerability to panic attacks. This can also apply to asthma patients to help improve their breathing techniques. Decreased PetCO2 can lead to a number of "autonomic, endocrine and metabolic disturbances, which contribute to the pathophysiology of asthma."

In treating asthma and hyperventilation patients, the basic theraputic priniciple is to "keep the PaCO2 high; if neccessary, make it high, and above all, prevent it from being low."

Chapter Twenty - Cardiopulmonary Resuscitation

Animal and human studies have shown a great correlation between ETCO2 and cardiac output during low flow states and during CPR.

When someone tires doing CPR the ETCO2 goes down, when a fresh resucer takes over it usually goes back up.

Patient's not rescusitated show a gradual dimminution of ETCO2 during CPR.

Routine monitoring of ETCO2 during cardiac arrest is preferable to palpating for carotid pulses in monitoring how well CPR is working.

While ETCO2 appears to mirror cardiac output, it may not be applicable to cerebral blood flow.

The administration of Sodium Bicarbonate will show a transient increase in ETCO2 that returns to baseline within five minutes.

ETCO2 may decrease following administration of epinephrine, possibly because of redistribution of blood flow duw to vasoconstiction and increased afterload. This decrease may actually be a good sign because it reveals the presence of vasomotor response.

No patient with an ETCO2 reading of less than 10 after 20 minutes of CPR was rescusitated in any of the studies done.

The higher the initial ETCO2 the better the chance for resiuscitation, but patients with low initial readings have survived.

A rise in ETCO2 is almost always noted prior to having a palpable pulse when a patient has ROSC.

Chapter Twenty-One Embolism

Pulmonary embolism increases alveolar deadspace. This deadspace can possibly be differentiated from deadspace due to COPD due to a difference in the upslope of the capnogram.

COPD

2006-03-31T04:00:00.000-08:00

Asthmatics and COPDers had a characteristic shark fin shape, which indicates resistance to expiration.

Yesterday we had an eighty-year COPDer with Sats in the 80's, alert, but not moving too much air. We gave her two back to back combi-nebs and monitored her with capnography. It was the first time I used capnography on a COPDer.

Keep in mind a slanted "shark fin" wave form shows the person is struggling to exhale through resistance. A more box like wave form shows no resistance. Here's a normal wave form and a bronchospastic wave form (from Oridion guide):

And here's our patient's wave forms, initially, during the first treatment(combi-vent, which bronchodilates) and after two treatments:

Way cool, I thought. It really shows how effective our treatment was. The woman felt much better and was breathing easier. The nurse at the ED asked what the funny looking cannula was for. She was impressed when we said capnography. We tried to show her the wave forms, but she just nodded, and it seemed to me the wave forms meant nothing to her. A couple weeks ago, they would have meant nothing to me, too.

-April 2006

Case Four: PEA or Low Cardiac Output?

2006-03-28T19:37:00.000-08:00

"A number of patients with the so-called pulseless electrical activity (PEA), actually have cardiac activity. More than eight of ten patients believed to be in PEA have synchronous cardiac wall motion, and over 40% have a measurable aortic pressure. (Bocka et al., 1988; Paridis et al., 1992; Cantineau et al., 1994). Capnography can help distinguish between PEA and very low cardiac output arrest states (Sanders et al., 1985; Isserles & Breen, 1991; Cummings & Hazinski, 2000.)"

- Capnography: Clinical Aspects; edited by J.S. Gravenstein, Chapter 8, Capnography in Transport, M.A. Frakes, Page 68;Cambridge University Press, 2004.

***
2 cases to talk about:

Case #1 happened last February and at the time I didn't know too much about capnography, and so I didn't add it all up.

I had intubated a patient with agonal respirations, who had now stopped breathing on her own and who now had no palpaple pulse and I couldn't get a blood presure. She was intubated so I was ventilating her, but she was a DNR so I couldn't start compressions. The full story is described in my medic blog under the heading Scenario.(The story describes the dilemna because the patient was a DNR, but not a DNI).

Here's what she looked like on the monitor:

Under normal circumstances we would start CPR under the PEA algorithm. No palpaple pulse, no BP, not breathing on own, unresponsive. However, while being ventilated the patient had an ETCO2 of 14-20 without CPR. In other words, capnography revealed she still had cardiac activity that was producing some output, albeit very low. Still, it clearly reveals that the patient is not in PEA. If this patient were not a DNR, without capnography, you would have no choice but to begin CPR. With capnography, maybe it raises some question about how to proceed. Do you just do a dopamine drip or do you do CPR anyway?

Case #2 I had a slightly different call a few months earlier where the patient was not a DNR.

Here's the initial rythm:

Not too good.

Initial capnography on intubation was 7. The patient got four epis and two atropines. The end tidal went up to 11, and then 25 at which time the monitor showed a rate of 130.

Still, now en route to the hospital, we could not feel a pulse or hear a BP. She had no respiratory effort of her own. The dilemna was without capnography this patient was still in PEA. Since I was new to capnography and didn't quite understand it, as we rolled down the hall to the ER, I did psuedo CPR (compressions but not deep or hard enough to crunch a rib) because I did not want to lose my medical control for not doing compressions on someone in PEA, but at the same time I felt there had to be some cardiac output to have a capnography reading of now 30.

(I apologize for the poor strips -- I was not collecting them at the time and have had to scrounge around in boxes to find these.)

Again keep in mind I had no training on capnography (beyond being told I had to put it on every intubated patient to get a wave form to show I had the tube in the proper place), and was struggling to think it through. I had never thought of or encountered such a situation. Today, clearly I would have said: her capnography is 30. She's producing carbon dioxide. She has cardiac output. She is not in PEA. As it turned out, they got a BP of 125/70. They ceased CPR.

My question (at the risk of asking a stupid question) that I need to run by some physicians is this: Prehospitally, lacking a dopler, but possessing continuous capnography, assuming we can't feel a pulse or hear a blood pressure and the patient has no respiratory effort of their own, how high should the capnography be(assuming no active compressions) before you can safely withhold compressions? You would clearly do compressions at 3, and you would clearly not do compressions at 35. What about 14?

***
UPDATE:

I encountered an excellent slide show on capnography by Dr. Strayer from McGill College. He includes the following slide:

Here are his comments:

"PetCO2 can differentiate between PEA and pseudo-PEA, which probably accounts for the majority of our PEA ROSCs, especially in cold water or overweight people, where pulse palpation carries a high false-negative rate. Ultrasound is probably a more useful modality in this application, however. In this graphic, the patient has no palpable pulses but a persistent PetCO2 of 20, without CPR (stopped at point A). CPR is restarted at point B, which doesn't do much. At point C, dopamine is infused. At point D, a pulse is palpated and cardiac compressions are halted."

Cardiac Arrest: Case Study Five

2006-03-26T17:25:00.000-08:00

6:03. Person not breathing. We arrive at 6:10, enter the house walk through a narrow hallway,and then down a narrow staircase, and then around some big furniture to a basement bedroom where the first responders are doing CPR.

The man is in his late fifties with a diaylsis port hanging out of his chest. He's warm. Family says he was talking to them shortly beforehand. A witnessed address. He's asystole now. I intubate him. End Tidal CO2 shows a good wave form with a reading between 17 and 23.

We work him hard. Doing the new CPR. I get an EJ and in go the drugs. Epi and Atropine. I give him some Calcium. Next thing I know the ET CO2 is up to 35. We stop compressions. He's got an organized rythmn and a pulse. BP is 124/80.

It is now 6:30 -- a half hour into the call. We have to package him. Fortunately we can go out through a backdoor, but there will be a hill to push him up. As soon as we get him outside, the capnography drops down to 18. Back to CPR. More epi/atropine. Capnography gets him back up. We lose him again as we push up the hill, but regain ROSC as we near the hospital at 7:00.

Pulling him out of the stretcher, something happens with the wheel release and the stretcher slams hard down on the steps. I look at the monitor. A good wave form. The tube is still good.

Going down the hall, he starts to fade out again, and even though his ETCO2 is 32, we start CPR. The rythmn looks idioventricular. They work him awhile longer at the hospital, but he doesn't make it.

The capnography was very instructive. It did the following:

1) Confirmed initial placement of the tube.

2) Alerted us to ROSC three times.

3) Whenever we were doing CPR and the number started to fall, we switched compressors and the number came back up. At one point, I told my partner if he could get the ETCO2 up from 16 to 20, I'd buy at Dunk'n Doughnuts. He started pounding the CPR and the number slowly climbed all the way up to 28. Stopped compressions, the number fell off the cliff almost right away.

4) Continuously confirmed placement of tube during transport and patient handling.

Hyperventilation

2006-03-11T03:29:00.000-08:00

Had a 22 year old under stress at work and home complaining of dsypnea, cold and numb extremities. Unable to move fingers. Put him on the capnography.

Respiratory rate of 40, ETCO2 of 26.

After coaching him to slow his breathing, hir respiratory rate went down to 10 and his ETCO2 went up to 40. The cold numb feeling went away and he was able to move his fingers again.

June Capnography Log

2006-03-04T03:30:00.000-08:00

June 27, 2006 Croup

5 year old asthmatic, not responding to his home nebs. Satting at 100% on room air, no wheezes, but a sore throat and barking cough. I gave him humidified 02.

Here's the strip. (He's having a slight inspiratory problem):

June 22, 2006 - Journal Club - Challenged

I just got back from our journal club, where we did three articles on ETC02, which I have listed under the monitoring section. I am a little discouraged because the club advisor, a doctor who I love discussing subjects with challenged me on the utility of capnography for the non-intubated patient and I didn't argue as persuasively as I thought I could. I am partially handicapped by my non-M.D. level of physiology understanding. His point was we need studies to prove the use of capnography in the field and that I shouldn't let it guide my judgement. I was trying to say that until the studies are done, I can at least let it help confirm my judgement. Capnography by itself is just a number and a wave form. It needs to be seen in the context of everything. The one benefit to being challenged is it will force me to sharpen my arguements as well as my understanding. It is new territory and I am learning something with each experience. I do wish I was more informed so I could be sure that what I am writing here is reliable and not BS.

June 22, 2006 - ?COPD ?CHF ?Pneumonia

77 year old female with increasing respiratory distress. Only respiratory history was COPD, but she sounded like she had rales. Pale diaphoretic, warm, some pedal edema. Heart rate 108. Respirations in the high 30's. Sat in the 80's. She had a nice straight up wave form. I held off on a treatment and held off on Lasix and just went with 02 by nonrebreather and nitro, and she started breathing much better. Heart rate and respiratory rate improved steadily. Sat came up to mid 90's. Did capnography change the way I practiced? No, but it gave me more confidence in not giving a treatment, which I am always leary of doing when I sense CHF. At the hospital she had a temp of 100.7.

Here's her trend summary of HR and RR.

June 21- Unresponsive, Fever, Hyperglycemia

Unresponsive Incontinent obese 30-year-old male with kidney transplant and insulin dependent diabetes, not taking his insulin for several days and with infected feet for which he was recently seen for sepsis. Patient is hot diaphoretic, temp of 103 at the hospital, pupils dilated non-reactive, our blood sugar was 377, hospital's was 666, HR-140, BP- 200/100, Respiratory rate between 25 and 45 over a minute, but at times almost apnenic. No fruity acetone breath. Patient thrashing around. Glascow Comma between 6 and 9. Extremely difficult extrication from basement during which as we carried the person vertically up steep stairs on scoop, I thought he had coded during period of apnea. In the ambulance, patient Sats at 99% on 100% 02, Capnography steady betwen 35 and 38. We don't have RSI, the patient had a gag reflex. After seeing capnography and SAT, I felt a little better about his prospects for coding on the way in. He was at least perfusing, and did not appear to be, in my guess, in extreme acidosis. At the hospital, he was paralayzed and intubated.

Below is a trend strip showing an erratic respiratory rate.

Here are some wave forms.

The forms are mostly upright, but note the irregularity. I have figured out that you can measure the respiratory rate of a single breath just as you measure a QRS complex, using your field guide. Just measure from end of inspiration to end of inspiration. In this brief segment (sorry for not capturing the apnea (I was carrying the patient or too busy doing other things) the respiratory rate ranges from 25 to 45.

What was the guy's problem? He was certainly septic. He was hyperglycemic, but he wasn't in DKA. His ETC02 was too high. If he was acidotic, his ETCO2 should have been lower. I checked back with the hospital later and found their lab work showed his arterial CO2 was 40. Pretty close to our reading. Unlike our differing blood sugar -- so much for our just calibrated glucometer. I wouldn't rule out neurological damage. I suspected maybe some drugs on board, but he was clean.

Here's two studies on ETC02 in diabetic ketoacidosis.

End-tidal carbon dioxide predicts the presence and severity of acidosis in children with diabetes reveals that ETCO2 can help discriminate between patients with DKA and those without. Bottom line, Children without DKA had a mean ETCO2 of 37, those with DKA had a mean of 22.

Capnometry for noninvasive continuous monitoring of metabolic status in pediatric diabetic ketoacidosis. In this study initial ETC02 of patients in DKA was 18.6 +/- 10.8 torr. They also concluded that ETCO2 in patients with DKA provided an accurate measurement on arterial CO2.

I will post this later as a case study.

June 20 - Concordance Between Capnography and Arterial Blood Gas Measurements

dnvermedic posed an interesting question in a comment on this blog.

we had a copd pt. today that was super-sick - had been sob for a few weeks and was getting worse. didn't go to the hospital because he couldn't get to a bus. ironically, we weren't there to see him - we were there to see his significantly less ill family member - saw him huffing and puffing in the corner and jumped on it.

anyway, he was breathing 40+ times a minute, sats were in the low-mid 80s on a nrb with a albuterol neb attached. we decided to put the capnography cannula on him and had a strangely normal looking waveform and a strangely normal co2 level. labs showed up later with co2 level in the 60s (i do realize abg will have a different # than exhaled co2, but still...) - besides copd, lung ca that was supposed to have been treated, he was also suffering from respiratory acidosis.

after this long babble, my question is this - have you heard of getting incorrect co2 levels when the waveform is good? i told the doc i was surprised to see that he didn't have high co2 levels on the capnogram, and the doc couldn't come up with an answer for that.

thought i'd ask...

I promised I would look into his question and get back with the best answer I could find. Again, I must state at the outset, that I am not an M.D. I’m just a paramedic trying to learn about capnography, and lacking a standard text written for paramedic addressing all our prehospital questions(I’m learning that there is much that no one really knows the answers too, because capnography is new to the emergency and new to the prehospital setting), I have to try to piece answers together.

Here goes.

Generally speaking, studies have shown that End Tidal C02 obtained through capnography correlates well with arterial blood gas measurements of carbon dioxide. The most recent study – of patients with acute asthma – showed a high concordance (see clinical Studies). Similar studies in the past have shown concordance for people with healthy lungs, pediatrics with upper and lower airway disease, people with seizures and diabetic ketoacidosis.

There seems to be a problem however in patients with severe lung disease who have an excess of dead space. This can cause a perfusion/ventilation mismatch. There is carbon dioxide in the blood that cannot be ventilated off because there are not enough healthy alveoli for the needed exchange to take place. Thus the blood gas will be higher than the End Tidal C02. The blood will be poor in oxygen and rich in carbon dioxide

For a more detailed explanation, click this e-medicine link:

Respiratory Failure

For a nice layman’s explanation go to this message board link:

In the textbook Capnography Clinical Perspectives, in Chapter 23: PetC02 Monitoring for Patients with ARDS, the chapter author describes:

a study of patients with ARDS (Acute Respiratory Syndrome) where end tidal C02 accurately predicted blood gases “for the majority of patients in the study (65% or 20 of 31) with mild to moderately severe forms of ARDS. PETC02 did not accurately predict PAC02 for patients with more severe forms of ARDS (35%) requiring higher levels of ventilatory support and more compromised arterial blood gas exchange."

The bottom line for EMS people is to keep in mind that for COPDers and other people with severe lung disease, our End Tidal numbers might not be as reliable an indicator of arterial blood gas as it is with other patients.

Additionally, in Chapter 30 of the text, Ventilation/Perfusion Abnormalities and Capnography, the author mentions several limitations to the accuracy of capnography. (He is writing about mechanically ventilated ICU patients, but this should also be applicable to EMS patients.)

1. The composition of respiratory gas mixture may affect the capnogram, such as the use of high 02 concentrations in critically ill patients.

4. Contamination of the monitor or sampling system.

7. A low cardiac output state may result in an artificially low PetCO2 value.

The chapter concludes:

“Mismatching of ventilation and blood flow is common, and may become very severe in diseased lungs...Capnographic features such as absolute PETCO2 value, capnographic wave-form interpretation, as well as the (a-ET)PCO@ differences need to be interpreted in view of the presence of V/Q(ventilation/perfusion) inequality from lung disease or hemodynamic factors."

In paramedic speak:

Capnography like all of our tools needs to put in the context of the whole picture.

Severe lung disease and low cardiac output can lead to lower End tidal C02 values than the actual arterial blood gas values.

And just how much high flow 02 affects the value? I don’t know. This might be a good area for a study.

Lacking that study, in my practice, I will try to follow up as much as I can and get an arterial blood gas value from the hospital and compare it to my ETCO2 value on interesting cases.

Thanks again to denvermedic for raising such an excellent question!

June 14, 2006 COPDer with reproducible back pain.

Went to a medical center where the staff treated a COPDer with reproducible back pain as if her were having an MI. In addition to bottoming his pressure for a period(prior to our arrival), he began to have some trouble breathing. His wave form was straight up -- no wheezing, but his C02 number was only 19-20. I upped his 02 from 2 to 3. His SAT went from 91% to 95% and his ETC02 went up to 30. He was breathing better. I'm going to try to make note of the changes in ETC02 in COPDers with 02 added.

June 10, 2006 - COPDer with Pneumonia

60 year old female in a nursing home with a history of Lupus and COPD. Extreme tachypnea. Rate of 60. Sat 88% on cannula at 2 lpm. Fever of 103. Lung sounds decreased, some rhonchi. No wheezing. Put her on the capnography.

ETC02 - 20. The waveform indicates rebreathing. She is taking a new breath before she has let out the last breath.

I put her on a nonrebreather at 15 lpm.

90 seconds later, her ETC02 has risen(28), along with her SAT (94), which is now 94%. Her respiratory rate declines to 37. The waveform is showing less rebreathing.

Eight minutes later, she has been doing much better. Her respiratory rate has stabilized -- still too high at 37. Her Sat is 99-100%, Her ETC02 is 32. Her wave form is upright.

When I tried to put her back to a cannula -- the same thing happened. Rebreathing wave form, increasing RR, decreasing SAT, decreasing ETC02. I put her back on the nonrebreather, everything straightened out.

At the ER, the nurse said I had her on too much 02 for a COPDer. I went over my findings, including the capnography, and also mentioned that the hypoxic drive therory was pretty much that -- just a theory that wasn't really bourne out by clinical findings. The patient stayed on a mask. X-rays confirmed massive pneumonia.

I came across an interesting article by a respiratory therapist named Jeff Whitnack called:

Death of the Hypoxic Drive Theory

Very interesting reading. Here's an excerpt:

In the May 98 issue of Clinical Pulmonary Medicine is an article titled Acute Respiratory Failure in Chronic Obstructive Pulmonary Disease” by Schiavi. In it the author concludes that…… “....The traditional idea that oxygen induces hypoventilation by suppressing hypoxic ventilatory drive at the level of peripheral chemoreceptors is no longer tenable.”

Here's the guy's home page, which includes a link to his powerpoint presentation.

Home Page

June 3, 2006

A tech at the hospital told me they were getting capnography machines and an -inservice had been scheduled.

I had a good trauma today -- a patient with a destroyed pelvis from a wraparound a telephone pole. Heart rate in the 150's. I keep wanting to put the capnography on, but there was always one more thing I had ahead of me on the priority list. I'm curious what kind of reading I would have gotten.

July Capnography Log

2006-03-02T03:50:00.000-08:00

July 28, 2006 - Hyperventilation

Had a 22 year old under stress at work and home complaining of dsypnea, cold and numb extremities. Unable to move fingers. Put him on the capnography.

Respiratory rate of 40, ETCO2 of 26.

After coaching him to slow his breathing, hir respiratory rate went down to 10 and his ETCO2 went up to 40. The cold numb feeling went away and he was able to move his fingers again.

July 25, 2006 -Capnography in Cardiac Arrest

See Case Study Five -- I've been waiting for a code with return of spontaneous circulation just to get the trend summary, and I finally got it. It was a great strip. Unfortunately, although we got the patient back three times, he didn't make it.

Dsypnea - COPD/MI with dsypnea, very slight expiratory wheeze, but she was breathing shallow and fast, with pursed lips, often breathing out before she had finished breathing in. Note the shape. One breathing treatment helped a lot.

July 19, 2006 - Capnography During Sedation and monitoring for Apnea

Capnography to Monitor for Apnea:

We intercepted with a basic unit for a possible cardiac arrest. It turned out to be a patient with end-stage cancer who was a DNR, but the family didn't have the paperwork. She had become unresponsive and they thought she had stopped breathing.

When I climbed in their ambulance I saw her she was breathing, but responsive only to pain. The crew said her BP was 80/50. I put her on the monitor to see a sinus rythmn and put her on capnography.

While I was going for an IV line, the apnea alarm went off.

I gave a sternal rub and she started breathing again.

Here's a strip of her declining respirations:

Capnography to monitor pain sedation meds:

As I mentioned earlier when I was in Ohio I met a medic from Texas whose service used capnography quite regularly and who had a protocol requiring capnography on all patients who recieve pain meds or sedation meds.

This patient was an 80 year old woman with kidney stones who got Morphine for pain relief:

Here's the pre-MS capnography:

Here's the post MS capnography:

The respirations widen out a little as she relaxes.

And the Trend summary:

Nothing spectacular, but a good practice to get into for all patient's who should be monitored for respiratory depression following medication administration.

July 11-12, 2006 National Registry Committee Meeting

I just attended a committee meeting at the National Registry. They selected nine field medics from across the country with various experiences and from various types of services to spend two days with a facilitator from Ohio State to do a duty/task analysis of what paramedics do to help develop a curriculm and tests based on the real world. I naturally pushed capnography as a needed technology. It was interesting talking to the other 8 field medics from all parts of the country. Some had been using capnography regularly -- one had even participated in field research, others still weren't using it. One guy showed me his pain protocol which required capnography on every patient requiring sedation. I also met an EMS Educator from Texas involved with the Biotel system. One of my first links at this blog was to the wave form page of their protocols.

Capnography Interpretation

July 8, 2006 - Back from Vacation

Back from vacation, but had no patients requiring capnography today, which is okay I guess because we are getting low on cannulas while awaiting our order. The night medic here is also excited about capnography and so I have competition for our limited supply of cannulas. Fortunately more should be on the way.

I spent part of the day, answering some email questions from a reporter doing a story on the non-hospital use of capnography for a trade magazine for respiratory care specialists. One of her questions was about the interface with the ER staff, and its possible my answer may surprise her. The answer being that most people in the ER have no idea what we are talking about when we come in spouting about wave forms and capnometers. The night medic has remarked on the same problem to me. It's going to be interesting to see how this progresses. Of our two major hospitals, one has capnography only for intubations and the other is getting equipment -- again only for intubated patients. The key will probably come only when more research comes out showing capnography's utility in the non-intubated patient. One of my goals this month will be to compile a list of research projects I would like to see involving capnography.

May Capnography Log - Learning Something New Every Day

2006-03-01T04:02:00.000-08:00

Trending - May 2006

Below is a trend summary from a CHF patient.

It is amazing we had this feature on our monitors for some time and I at least never knew about. I have been trying to spread the word, and have only found one other medic who knew about it.

For any of you with Lifepack 12's out there, do the following:

Hit Options.

Hit Print on the options menu

Hit Report, which on ours is defaulted to Code summary.

You should get a trend summary option. Hit that.

Then hit print again on the options menu and the trend summary should print out.

I have found one monitor that doesn't have the trending software on it. Yours may or may not, but if it does, that's how to get it.

Looking at this trend summary, you can see the gradual reduction in heart rate (3rd graph), as well as the early SAT readings and later ones(4th graph). Next time I will try to get the capnography(5th graph) on in the room, rather than waiting to get out to the ambulance, as well as trying to keep the pulse SAT on.

Monitoring During Hand Held Treatments --May 6, 2006

I learned today you cannot use capnography on a person getting a handheld treatment. They have their mouths wrapped around the mouthpiece and so all the CO2 is coming out the extension. The CO2 cannula picks nothing up and all you get is a straight line and the apnea alarm going off every two minutes. You can of course monitor them before and after every treatment, but if you want to monitor them during the treament, you have to do the neb through a mask.

I used capnography twice today. First on an asthmatic COPDer, who had no wheezing, just chest congestion and chest pain. She had a small shark fin that showed only minute changes after the one treatment I gave her. Her numbers were around 35.

The second time was on a COPD/pneumonia lethary. Very decreased lung sounds. Blood pressure of 90/60 with poor cap refill. He was breathing about 22 times a minute with a number is the low to mid twenties. He had a shark fin. I wish I could print out the screen forms as they are so much more compact than the printout. The shapes look completely different.

Mouth Closed - May 7, 2006

Had a call for decreased mental status in an elderly DNR patient with a COPD history. He was breathing in a strange way. He wouldn't open his mouth, so his exhalation would puff up his cheek's like a frog, then the air would go up out his nose. It produced a capnography wave similar to a bronchospasm. When I made him open his mouth to breath, his wave form straightened up.

How do you spell that? - May 15, 2006

No indications for capnography for a few days. I should probably put together a list of indications for capnography. I went to a university medical school bookstore today and asked if they had any books on capnography. The manager said "What was that word?" I had to spell it for her. They had nothing in stock, just one you could order, which I already have. I'm trying to gather articles on capnography for our next journal club. The only good ones I can find pertain to intubation. The medical advisor to the club emailed me asking where are the articles on asthma and nonintubated patients. I told him I'll keep looking.

Dehydration - May 19, 2006

79 yer old woman at the doctor's office, weak and not eating for three days with vomiting. Short of breath. Clear lungs. Has a pacemaker. The cops had her on a nonrebreather, but the nurse had taken off so she could use the bathroom. She didn't appear to be having much trouble breathing and was initially Satting at 98. Down in the ambulance, her SAT dropped to 90 and she started too seem a little short of breath. I put her on a cannula and then when she still seemed short of breath, I put her back on a nonrebreather. Her capnography was consistently 20 throughout with a good wave form. Her respiratory rate varied from a low of 28 to the 50s. The rapid ventilations would make her number low, but it was low even when she wasn't breathing that fast. Her BP was okay, although she was dizzy when she stood. She didn't feel like talking much in the way that people who are sick and worried don't like to talk. I am curious what else may have been going on. I guess I am learning that capnography is just a single factor to try to add to the big picture and that capnography as with other vitals, the trend is often more important than the number, although the number can also be quite significant.

May 28, 2006 - Conversations
Back safely from the Medical Mission to the Dominican so I hope to start posting more on capnography. The night medic told me he had a COPDer with ETC02 in the 60's and an odd shaped wave-form, but he didn’t print the strip. I am going to try to enroll other medics in sharing their experiences with me and saving strips. The more strips I get and stories I hear, I can try to figure out what is normal and what is not for specific conditions and situations. He has been having the same experience I have where no one in the ED has any idea what the funny looking thing under the patient's nose is and what the capnography numbers and shapes look like.

I had a couple conversations with the nurse anesthetists on the medical trip about capnography and I was telling them how if I got a number 15 or above to start I was happy. One looked puzzled and said we always try to keep our number much higher. I said I'm taking about dead people.

Just before I left on the trip I received the following book I bought used from Amazon:

I will try to go through the book and post my notes as I go. It is not particuarly geared towards EMS.

May 29, 2006 - Weak Heart

Put it on three people today and yesterday. I got normal readings and wave-forms from a 22 year old diaylsis patient who was lethargic and vomiting and an 80 year old male with lung cancer. I got an upright wave form, but a low number reading of 25 in an 80 year old male with a weak heart (1/3) capacity according to wife, and who's defib had fired six times until I got some amio in him and stopped it. Poor cardiac output low number. Makes sense. He ended up at 29.

May 30, 2006 - Pneumonia

85 year old witha history of aspiration pneumonia. Audible rhonci, except for moments when he has coughed and he seems to have cleared some of the gook in his lungs. Respiratory rate 24. SAT of 80% went up into the 90's with a nonrebreather. BP 80/40. HR - 112. No pedal edema. NO CHF or COPD history. Breathes as well flat as sitting up.

His initial wave form is okay:

Then as the rhonci gets more audible, his wave form changes to a shark fin or a climbing wave form.

Then when he clears the gook for a moment, his wave form straightens out.

His capnometer was around 25. Poor cardiac output as evidenced by his pressure.

Capnography and Intubation

2003-11-27T16:38:00.000-08:00

When I was at a conference this past year one of the speakers said the data on prehospital intubation is so bad that if EMS had to go before the FDA to get approval to allow medics to intubate, it would be denied. Based on those studies, which include the LA pediatric intubation study, as well as many RSI studies, I can understand why.

However, those studies (to my knowledge) did not incorporporate continuous wave form capnography.

I believe continuous wave form capnography will eliminate all unrecognized misplaced tubes.

Capnography will prevent hyperventilation in head injured patients and critically injured patients(which may be the reason the RSI studies have poor results -- by letting medics intubate patients, RSI puts them at increased risk for hyperventiulation which is much easier to do with an patent airway and an ambu bag just begging to be squeezed.

And capnography can aid in the placement of difficult intubations. It can help prevent multiple attempts and even momentarily delayed recognition of misplaced tubes -- all of which cost the patient critical time without effective oxygenation and ventilation.

I believe continuous wave-form capnography will be the savior of prehospital intubation.

***

When many of us were taught to intubate the golden rule was:

NEVER PASS THE TUBE UNLESS YOU VISUALIZE IT PASSING THROUGH THE CHORDS.

The only ways we had to verify our tubes back then were this mantra, listening to lungs sounds and absence of belly sounds, looking for chest rise and mist in the tube -- all methods that cannot be considered fully reliable. My safety net was a partner who always held crick pressure for me and could tell me if I was in when he felt the tube pass under his fingers. That was my most reliable confirmation, but we didn't work together every shift so it was only part-time reliability. We didn’t have the bulb syringe then or colorimetric capnography much less continuous wave-form capnography.

While we all tried to live the mantra of never passing the tube unless we saw it pass through the chords, not all our tubes were in. Hopefully we recognized them right away – either by not hearing lung sounds or having warm gastric contents come flying up the tube to tell us we weren’t where we were supposed to be. How many times did we legitimately think we had passed the tube through the chords and how many times had we hoped we were through? Does the phrase “I think I’m in” sound familiar? particuarly coming from precepting or student medics?

As was proven in a recent study (see below), capnography has the ability to reduce misplaced ET tubes to zero if used. Instead of answering “You think! Pull it out!" or "You’re better hope you’re in – My license and mortgage and food in my babies mouths are riding on it!" Now capnography will tell you. He thinks right or he thinks wrong.

What I am going to suggest now is controversial. It stems from an interesting discussion I had with an articulate commenter on the November log. I suggest that with capnography’s ability to so quickly confirm or disprove a tube that it might no longer be a sin to pass the tube if you are not sure – particularly in the context of the difficult airway. If it wasn’t difficult we would easily see the chords, right? Now I’ll admit to shoving a tube or two in in my time. When you’re looking down the bloody throat of a gunshot or highway crash victim and you can’t tell what you are looking at or when puke and vomit are rising like a biblical Mississippi flood, sometimes you just put it where you think you see air bubbles or where anatomy wise the chords should be. When your own body is crooked trying to get an airway into the man wedged behind the toilet, sometime the view isn't the best. Ever tried an ice pick style tube?

In people whose chords are hard to see and who are difficult to bag, maybe the best thing to do is just shove the tube in to the best of your ability. And now with capnography, you’ll know you’re in or out almost instantly. Blind tubes are not after all that unusual in EMS. I have done digital intubations, intubations with a bougie and nasal intubations. All blind. I did them that way because that was the only way to get the tube. (Sometimes with IVs on people in extremis, you take a blind shot based on anatomy.) I say if you only have a partial view of the chords or the chords get obscured when you try to pass the tube, go for it if you think you can get it – as long as you have capnography to immediately check the tube.

***

Now here’s a tip. I haven’t done it yet in the field (it only occured to me the other day), but I think I will try it the next time I have to intubate a breathing patient. I have tested the concept and believe it will work.

Before you intubate, attach the capnography filter to the end of the ET tube, insert the stylet – it will fit as long as it is the thin kind, hook up the capnography to the machine, turn it on, and then go in for the tube. If your partner knows how to read wave forms he should be able to tell you if you are in or not when you ask. Either that or listen to the apnea alarm or the lack of an alarm. Make certain you have at least four good wave forms, and then pull the stylet and proceed with your routine checks.

For apneic patients you just have to have your partner ready to attach the ambu bag when you ask. No more looking around for the capnography filter -- it is already in place. Keep in mind as always for pulseless patients you may need a little CPR to get your wave form reading. And of course, you'll need to pull the stylet before you bag the patient.

Make certain you have an extra capnography filter available as backup because if by chance you miss your tube abd gastric contents come up, they will contaminate your filter in addition to your tube.

This method of attaching the capnography filter to the ET tube before intubating also works for nasal tubes. Watch the wave forms as you advance the tube while listening for respirations Once you think you are deep enough and then cough gag and you push through, verify with the wave forms. Just make certain you are not still in the hypopharanx.

***

Don't misunderstand me. I still believe you should strive for the gold standard of watching the tube pass through the chords. Don’t make capnography your crutch, but in a difficult airway, it may be your new best friend.

***

Postscript: The next morning my first call ended up being an intubation in which I used capnography to help intubate.

The call was for unresponsive patient with severe dsypnea. We found an 80 year old female with a GSC of 4-5 breathing at a rate of 60 with cool extremities. Unable to hear BP. Heart rate on the monitor 130-140. Blood sugar - 213. I attached the capnography filter to the end of the ET tube. Some of our ET tubes come with stylets already in them. I removed the stylet, but could not put it back in because it was to thick, so I used a thinner stylet. I went in, and had a hard time getting the woman's jaw open enough to see the chords. We don't have RSI so there was what we call inadequate relaxation. I could just barely see the chords under the epiglottis, but couldn't get the tube to pass through. Instead of checking by assessing breath sounds, I just looked at the monitor. The ETCO2 would just go straight and I'd know I had gone below the chords. I ended up nasally intubating her, which I probably should have done first, but I like to get a bigger tube in. The nasal tube went in great. I used a 6.0 and watched the wave forms as I fed it. The form went down to nothing, I pulled back and repositioned her head and then advanced the tube again, and felt it go through and had the big wave forms to confirm it.

Her SAT went up to 98% from the 80% and her ETCO2 came up from the mid twenties to low to mid thirties. She opened her eyes by the time we were in the ED.

(The next time I do a nasal tube I am just going to hit print button on the monitor from the start so I have a long strip to cut up and show the wave form changes.)

I'm still waiting to hear what was wrong with her - most likely sepsis.

***

Misplaced Tubes

The effectiveness of out-of-hospital use of continuous end-tidal carbon dioxide monitoring on the rate of unrecognized misplaced intubation within a regional emergency medical services system.

Silvestri S, Ralls GA, Krauss B, Thundiyil J, Rothrock SG, Senn A, Carter E, Falk J. Annals of Emergency Medicine, May 2005, pgs 497-503l

If there ever was an argument for requiring continuous ETCO2 monitoring on all intubations, this is it. Over a ten month period, in 11 counties in Florida there were 153 intubations. 93 (61%) used continuous ETCO2 Monitoring. 60 (39%) did not. Upon arrival at the Emergency department there were 14 (9%) unrecognized misplaced intubations. There were 0 (0%) misplaced tubes in the group that used continuous ETCO2 monitoring. There were 14 (23%) in unmonitored group.

The authors wrote: “The unobserved unrecognized misplaced intubation risk difference is compelling. This study demonstrates that it is possible to attain a zero unrecognized misplaced intubation rate.”

Four years earlier, another study was done in Florida that showed during an 8 month period out of 108 “intubated” patients brought to a large Florida ED, there were 27 misplaced tubes (27%) on arrival at ED. 18 were in the esophagus, 9 in hypopharanx. 17 of 18 esophageal intubations had an absence of expired CO2, the one with CO2 was nasally intubated and breathing their own. 4 of 9 hyphopharengal intubations had an absence of expired CO2. - Katz SH, Falk JL, Misplaced endotracheal tubes by paramedics in an urban emergency medical services system, Annals of Emergency Medicine, January 2001

The authors wrote: “The incidence of out-of-hospital, unrecognized, misplaced endotracheal tubes in our community is excessively high and may be reflective of the incidence occuring in other communities...Functionally, whether the tubes were misplaced initially or dislodged en route to the hospital makes little difference to the patient....Despite written protocols requiring the out-of-hospital use of ETCO2 devices in our community, we...found their use to be sporadic... We believe that routine use of this technique, both at the time of intubation and as an ongoing monitor during transport, could potentially eliminate the problem of unrecognized misplaced ETT placement....”

Bottom Line: Intubated patients should all have continuous ETCO2 monitoring.

Case Studies

2003-02-04T10:45:00.000-08:00

COPD

Cardiac Arrest

PEA or Low Cardiac Output

Apnea

Hyperventilation

Morphine

Cannula Position

Hypoxic Drive

Cardiac Output

Hypoventilation, Not Hyperventilation

Seizure

DKA

Capnography in Cardiac Arrest

2002-07-25T18:03:00.000-07:00

DKA

2002-02-04T12:21:00.000-08:00

50 year old female, slightly disoriented, difficulty breathing. ETCO2 - 17. RR- 30-50. Here's the strip and trend summary:

No history of diabetes, but recently put on prednisone.

Blood sugar - 600.

Seizure

2002-02-04T12:19:00.000-08:00

Called for a seizure. We found a postictal 80 year old man. No prior historyof seizure, who they said fell the night before, but hadn't appeared injured. Out in the ambulance he started seizing again. I managed to get a 24 gauge in his arm just as he stopped seizing. I had the ETC02 on and was watching his respirations now. He didn't look like he was breathing. It was more sort of burping.

I'm not certain what the little bumps represented -- the burps possibly, but I believe now I just had the cannula too deep in his nose and not enough over his mouth. I repositioned it, as he started taking deeper breaths. His end tidal was 80.

His breathing was very irregular, sporadic.

I kept waiting for him to snap out of it, but he wasn't coming around. I tried bagging him for a little bit, and then decided just to intubate him. I attached the capnography filter to the top of the ET tube, put in the stylet and went in. Saw the chords, saw good wave form on the monitor and I was good. I bagged him and got his ETCO2 down to 35.

He started bucking the tube a little so I gave him some versed.

At the hospital they said he had been in the hospital for a subdural hematoma a month before, so he may have been bleeding again.

Here's the trend summary for ETCO2 and RR:

Note: The apnea period includes a period where his nasal monitor is off and the ET tube isn't in yet. I have to unplug one filter, plug in the other and then I won't start getting a reading until I go in with the tube.

What lesson did I learn from the capnograpy? It alerted me that he was hypoventilating and his respiratory pattern was sporadic and ineffective. I was much more aggresive with the airway than I might have been based just on naked eye observations.

Hypoventilation not Hyperventilation

2002-02-04T12:17:00.000-08:00

We were called for an OD, unconcious, but when we got there we found a 32-year-old extensively tattooed woman standing, looking slightly dazed, saying she was having trouble breathing and just needed an inhaler. I listened to her lungs (in the lower lobes) and they were clear, which I announced to the assembled room of five firefighters, my partner, two cops, and three bystanders. Then with the next breath, she coughed and sounded very rhoncorus to the naked ear. "She doesn't sound clear," one of the bystanders said like I was an idiot. "She's talking fine," I said, "using complete sentences." Then I asked the patient what hospital she wanted to go to. She said she didn't want to go, she just wanted a treatment. I said, we don't do home treatments, if she was having trouble breathing we needed to take her to the hospital. Now in the meantime, I am hearing one of the bystanders explain to my partner that someone had found her unresponsive in the bathroom with blood all over the floor and walls that she either vomited or coughed up. I looked in the bathroom, only to see a woman just finishing cleaning it all up. The patient still just wanted a treament, but with the help of the cops, we insited she go with us. I helped her walk down one flight of narrow stairs down to where we had the strethcer. She wanted to walk to the ambulance -- at the same time she was begging with me to give her a treatment. We had her lay on the stretcher and I set the back up straight. Out in the ambulance, I put her on the pulse ox, and while her fingers were cold -- it was a wet, raw day, the pulse ox read less than 50, and then got up to 70. She was really sort of panicking now, and I listened again to her lungs - this time to the upper lobes and oh, my -- they were coarse and rhonocous and nasty. I put her on the capnography thinking that I would see low numbers, and this is what I had. ETCO2 - 70!

She got more and more panicky as I gave her a treatment by mask and had my partner drive lights and sirens the three blocks to the hospital, where we raced her in. The triage nurse and the other crew waiting in line looked at me maybe like I was crazy as I insisted we cut in front and that my patient was in true distress and not just your typical anxiety attack. I had to explain about the capnography -- why she wasn't hyperventilating and how I though maybe she has aspirated. They sent us down to a priority room, where I got the same looks and had to again explain that this wasn't what it first looked like. The doctor listened to her lungs -- lower lobes -- while a nurse coaxed her to slow her breathing down, and I had to have them listen to the upper lobes and show them they she was in fact hypoventiliating.

It didn't take them long to understand and see she was hypoxic. She then coughed up some blood and then admitted she had done two bags of heroin. I will try to check back to find out the final story, but the respiratory therapist agreed he thought she probably had aspirated.

The bottom line for me was while I was at first poo-pooing her complaint -- she appeared after all the typical junkie whiny borderline asthmatic anxiety type with a chest cold, the capnography slapped me in the face to what maybe I should have been seeing all along. It screamed out -- she is having a big problem!

I gave her a treament, which didn't seem to help her too much, although her ETCO2 number did come down into the high 50s. Her respiratory rate also picked up, which may have driven the number down some.

Just why the number was elevated, there are a number of possibilities. She had possibly been apneic before being found, her tachycardia -- 136 -- increased cardiac output drove the C02 number up, the aspiration tired her and limited air movement.

Cardiac Output

2002-02-04T12:15:00.000-08:00

80 year old patient altered mental status, altered breathing, possible aspiration. You can hear the rhonci from the doorway. DNR, supportive care only. Staff at Nursing home says patient's pulse - 112, BP 160/100.

Here's the quick look.

RR - 32 ETCO2 -14

We couldn't feel a pulse or get a BP.

Here's his ECG:

Hypoxic Drive

2002-02-04T12:09:00.000-08:00

Called for a man with lung cancer and COPD. He was satting in the low 80's on his home 02 with slight wheezing. We put him on a nonrebreather when his sats didn't improve with a few more liters by cannula. While his SAT went up to 100%, his end tidal also went from 37 up to 52, and his respirations dropped slightly. The point of all this is for all the debate about the hypoxic drive and not giving COPDers too much 02, if you are at a nursing home or a doctor's office and they tell you not to give over 2 liters while you are putting a mask, you can just say, not to worry, you are monitoring the patient's ventilations with capnography. If the ETCO2 gets too high indicating hypoventilation, you can turn the 02 down. If the patient is normoventilating, you can leave it high if the extra 02 makes them more comfortable.

Here's the trend summary (HR, SP02, ETC02, RR):

Initial capnograph:

On nonrebreather:

Cannula Positioning

2002-02-04T12:06:00.000-08:00

The positioning above produced the following wave form:

Due to the patient's mouth breathing, the cannula was then repositioned.

And the new wave form:

Thanks to bdmedic for submitting.

***

February 25, 2007 - Cannula Positioning

Today I had an elderly patient with CHF. The initial end tidal was 8, but quickly jumped to 30 when I repositioned the cannula because the patient was a mouth breather. I put a non rebreather on and the number went down to 20. Several times during the call, the numbers moved, and each time when I repositioned the device the numbers came back to near 30.

(The other day I heard a medic patch in with a patient with stable vital signs but an ETCO2 of 9. Positioning of the cannula was probably the issue.)

The point of all this is that positioning the cannula is very important if your reading doesn’t seem right. It can be affected by a patient’s unique anatomy, by the patient’s method and manner of breathing and by their anxiousness during transport, which can shift the cannula position. (The position will affect not only the ETCO2 number but the RR number.) This patient had an initial RR of 48, which gradually came down to 38 due to some NTG SL, which seemed to help the breathing. The ETCO2 rose to 32, and settled there, which I was happy with considering. I stayed alert to make certain the RR wasn’t declining due to the patient growing more tired. Her effort in breathing seemed a bit more relaxed.

This all goes along with what I wrote below about normal values. You can't just always accept the numbers at face value and compare them to traditional norms.

February 20, 2007 - Normal Values

The normal values for ETCO2 are listed at 35-45 mm Hg. I have read that they are really 33-43 due to the possible gradient between arterial Co2 and ETCo2. What is normal anyway? Normal HR is 60-80, Bp 110/70-130/80. It all depends on the person obviously. But as I don't get too concerned with a HR of 88 or a BP of 140/90, I think you have to take the same approach with ETCO2. Most of my patients have ETCO2 in the 28-35 range, it seems. It is an emergency situation and usually they are a little short of breath -- that accounts for it. Sometimes the 02 dilutes it a little. I guess all I'm saying is normal is different for everyone to a point, and that in the emergency setting, it is not uncommon to have many people outside the normal range. I am most concerned with extreme readings that are trending worse.

***
Check out this letter exchange in the March Respiratory Care concerning the accuracy of the nasal ETCO2 cannulas. It brings up some concerns I have had about the accuracy of the nasal cannula versus the intubated filterline.

Morphine

2002-02-04T12:03:00.000-08:00

Capnography monitors respirations and ventilation -- important information when you give a patient a possible respiratory depressant.

I had an 80 year old woman with a broken hip in extreme pain. She had taken one tramadol, which obviously hadn't touched her. I like to premedicate the patient before I even try to move them so, in increments, I gave her 7mg of Morphine over ten minutes. I waited about five minutes more, and then we packaged her on a scoop stretcher. Out in the ambulance she was still in a fair amount of pain and the roads we were on were pretty bumpy so I called to get permission to give her 3 more mg, and I was pleased the doctor actually told me to go ahead and give her 5 more mg. (We can give up to 0.1 mg/kg on standing order, and have to call for more.)

The extra morphine worked wonders. I had her on capnography to monitor her respirations/ventilation. By the time we got to triage, while she was still awake, she was feeling no pain and her respirations, which had been in the high twenties were down to 8. Her ETCO2 remained constant.

Here's the wave form strip:

Here's the trend summary for ETCO2 and RR.

Capnography in Critical Care

2002-02-03T08:54:00.000-08:00

Interesting Article from Respiratory Care(2007 Apr;52(4):423-442)

Should Every Mechanically Ventilated Patient Be Monitored With Capnography From Intubation to Extubation

"The pro position is supported by the physiology of the V/Q relationship in the lung and capnography's ability to prevent airway mishaps. On the other hand, the con position is supported by literature that brings into question the relationship between PETCO2 and PACO2 in the clinical setting."

Update History

2001-03-26T03:27:00.000-08:00

This is a new page where I will archive the What's New page.

April 16, 2007

Interesting Article from Respiratory Care(2007 Apr;52(4):423-442)

Should Every Mechanically Ventilated Patient Be Monitored With Capnography From Intubation to Extubation

"The pro position is supported by the physiology of the V/Q relationship in the lung and capnography's ability to prevent airway mishaps. On the other hand, the con position is supported by literature that brings into question the relationship between PETCO2 and PACO2 in the clinical setting."

***

April 6, 2007

Check out this letter exchange in the March Respiratory Care concerning the accuracy of the nasal ETCO2 cannulas. It brings up some concerns I have had about the accuracy of the nasal cannula versus the intubated filterline.

Two new interesting strips in the April 2007 Log.

***

March 27, 2007

10 Things Every Paramedic Should Know About Capnography has been updated, including new sections on CHF, the Hypoxic Drive, and Sedated Intubated Patients, as well as adding clarifications and cautions on other topics. I have labeled this version 6.0 and will probably be doing some minor rewrites periodically, and will label those 6.1, 6.2 etc. I also hope to put the document in a word file and make it available for download. I hope to do that within a week.

March 26, 2007

New Web link:

Capnography/capnometry during mechanical ventilation: 2003 revision and update.

Check the March log for an excellent comment revieved from a reader on the CHF/COPD wave form question:

March 2007 Log

March 19, 2007

Two New web links:

Capnography Research in Asthma

Wikipedia: Capnography

One new study:

Mainstream versus Sidestream Monitoring in the PACU

To read my notes from Bob Page's "Slap the Cap" Cagnography Presentation and other highlights from the JEMS Conference, as well as recent calls, go to the March log.

March 2007 Log

Mainstream vs. Sidestream

2001-01-02T13:47:00.000-08:00

Evaluation of a compact device for capnometry of main-stream type compared with one of side-stream type in a postoperative care unit

An article from the Japanese journal Masui, concludes that mainstream monitoring is more accurate than sidestream in monitoring breathing in the recovery room. Sidesstream gave 5 false apnea readings.

I haven't been able to get the full study, but from my experience, can tell you I have had the sidestream apnea alarm go off at times even when the patient was breathing. While I believe the nasal cannula capnography is very important, it is not completely reliable due to positioning and patient anatomy.

Capnography and Critical Care Transport

2001-01-01T09:46:00.000-08:00

Utility of a novel quantitative handheld microstream capnometer during transport of critically ill children

Am J Emerg Med. 2006 May;24(3):302-7. Singh S, Allen WD Jr, Venkataraman ST, Bhende MS. Division of Pediatric Emergency Medicine, Children's Hospital of Pittsburgh, Pittsburgh, PA

A partial abstract:

RESULTS: Fifty patients comprised the study group, ages birth to 15.3 years (median, 4 months) and weighing 1.63 to 70 kg (median, 5.25 kg). Nineteen patients were transported by ground ambulance and 31 by rotorcraft. The capnometer confirmed ETT position during transport in all patients. The audiovisual alarm of the capnometer immediately detected a ventilator disconnection from the ETT during one air transport. The size of the device was evaluated as "just right" in 37 of 50 transports, "easy to secure" in 46 of 50, and "useful" in all 50 transports. There were no false-negative readings, occlusion, or kinking of tubing during transport. NPB-75 was specifically useful for setting optimal ventilatory support in 2 patients with raised intracranial pressure who required controlled ventilation. Furthermore, it confirmed adequate ventilation when the ventilator falsely detected a low respiratory rate in a newborn with a congenital heart disease for whom pulse oximetry was unreliable. The ETco(2) waveform detected air trapping in 2 ventilated asthmatic patients. CONCLUSIONS: This lightweight microstream capnometer with a 4-hour battery life and audiovisual alarms functioned well in the prehospital setting. It provided both quantitative and graphic real-time detection of ETco(2) in intubated patients, which was of critical importance for the optimal management of patients during transport.

Bottom Line: This study showed the utility of using a small handheld capnometer, a device, which measured only the ETCO2 number during transport of critical care patients.

Capnography and Gastroenteritis

2001-01-01T09:44:00.000-08:00

End-tidal carbon dioxide as a measure of acidosis among children with gastroenteritis

Pediatrics. 2006 Jul;118(1):260-7
Nagler J, Wright RO, Krauss B.

CONCLUSIONS: End-tidal carbon dioxide levels were correlated with serum bicarbonate concentrations among children with vomiting and diarrhea, independent of other clinical parameters. Capnography offers an objective noninvasive measure of the severity of acidosis among patients with gastroenteritis.

Bottom Line for EMS: Another possible use for capnography. (I have only read the abstract of this article. I will be trying to get a copy of the whole article to get a better understanding of this.)

Capnography and Trauma

2001-01-01T09:40:00.000-08:00

Prehospital end-tidal carbon dioxide concentration and outcome in major trauma

Deakin CD, Sado DM, Coats TJ, Davies G.,J Trauma. 2004 Jul;57(1):65-8

BACKGROUND: End-tidal carbon dioxide (Petco2) concentration is a marker of the pathophysiologic state because it is a reflection of cardiac output. Petco2 correlates with outcome after prehospital primary cardiac arrest, but association with outcome from prehospital trauma has not been established. METHODS: Between 1998 and 2001, Petco2 was recorded in 191 blunt trauma patients requiring prehospital intubation. Rapid sequence intubation was performed using suxamethonium (1 mg/kg) and etomidate (0.2-0.3 mg/kg). Initial Petco2 after endotracheal intubation (t0) and Petco2 at 20 minutes after endotracheal intubation (t20) were recorded, together with survival to discharge. RESULTS: Median Petco2 at t20 was 4.10 kPa in survivors and 3.50 kPa in nonsurvivors (95% confidence interval of difference between medians,). Petco2 at t20 was a better predictor of outcome than at t0. CONCLUSION: Only 5% patients with Petco2 less than 3.25 kPa survived to discharge. Petco2 at t20 is of value in predicting outcome from major trauma.

Here's an article about the study by Bryan Bledsoe, D.O.

ETCO2 and Trauma

Bottom Line for EMS: ETCO2 again can help predict severity of injury and outcome.

Capnography in DKA

2001-01-01T09:39:00.000-08:00

End-tidal carbon dioxide predicts the presence and severity of acidosis in children with diabetes

Acad Emerg Med. 2002 Dec;9(12):1373-8
Fearon DM, Steele DW.

CONCLUSIONS: End-tidal CO(2) is linearly related to HCO(3) and is significantly lower in children with DKA. If confirmed by larger trials, cut-points of 29 torr and 36 torr, in conjunction with clinical assessment, may help discriminate between patients with and without DKA, respectively.

Capnometry for noninvasive continuous monitoring of metabolic status in pediatric diabetic ketoacidosis

Crit Care Med. 2003 Oct;31(10):2539-43.
Garcia E, Abramo TJ, Okada P, Guzman DD, Reisch JS, Wiebe RA.

CONCLUSIONS: PetCO2 monitoring of patients with diabetic ketoacidosis provides an accurate estimate of PCO2. Noninvasive PetCO2 sampling may be useful in patients with diabetic ketoacidosis to allow for continuous monitoring of patients.

Bottom Line for EMS: Put your cannulas on hyperglycemic patients.

Identifying Airway Disease

2001-01-01T09:23:00.000-08:00

Capnogram shape in obstructive lung disease.

Anesth Analg. 2005 Mar;100(3):884-8

Krauss B, Deykin A, Lam A, Ryoo JJ, Hampton DR, Schmitt PW, Falk JL.

Division of Emergency Medicine, Children's Hospital-Boston, MA

262 people at a pulmonary laboratory received capnograms and pulmonary function tests(forced expiratory volume in 1 second (FEV1)). People with obstructive disease(OD) had capnograms that “were significantly different” from normal and Reactive Airway(RD) patients.

The authors write: “These differences were progressive, increasing with disease severity… Differences between OD capnograms and normal and RD capnograms, correlating to changes in FEV(1), were sufficiently large enough to suggest that the capnogram could be used to discriminate between OD and normal."

Patients were categorized as either Severe OD, moderate OD, RD or normal based on their FEV1 and FEV1/FVC scores.

• FEV1: Forced Expiratory Volume in 1 Second - This is the amount of air that you can forcibly blow out in one second, measured in liters. Along with FVC it is considered one of the primary indicators of lung function.
• FEV1 / FVC - This is the ratio of FEV 1 to FVC. In healthy adults this should be approximately 75 - 80%.
Here is an excellent description of what happens in the plateau phase of expiration:

“The plateau phase of the capnogram reflects the passage of air from progressive emptying of the aveoli. Normally alveoli are equally ventilated and all have similar CO2 concentrations, so the capnogram has a nearly constant value throughout this phase of exhalation. In OD, some terminal bronchi are narrowed, resulting in local hypoventilation of alveoli and an associated increase in their CO2 concentration. Alveoli attached to unobstructed terminal bronchi are relatively hyperventilated and have diminished C02 concentrations. During exhalation, unobstructed alveoli empty ahead of obstructed ones, leading to a progressive increase in CO2 concentration during exhalation. This uneven emptying of alveoli gives the alveolar plateau a characteristic sloped appearance in OD.

“In RD, the airflow in the earliest portion of exhalation approximates that of subjects with normal lung function. Thus, the initial expiratory phase, in the first 250ms, is unchanged. Subsequent flow rates are progressively reduced because of because of diminished lung volume, resulting in diminished FEV1 in RD. However because the terminal bronchi are unobstructed and homogeneous, the alveoli empty evenly, leading to a low alveolar slope and angle. Taken together, these effects result in capnograms that are similar to those obtained from normal subjects, despite severe decreases in FEV1 in the presence of RD.”

Bottom Line: A simple study to show that simply by looking at the wave form, it was possible to detect who had obstructive airway disease and who did not. This helps confirm the utility in using capnography in addition to clinical judgement in determining if obstructive airway disease is present.

***

Utility of the expiratory capnogram in the assessment of bronchospasm

Ann Emerg Med. 1996 Oct;28(4):403-7. Links
.Yaron M, Padyk P, Hutsinpiller M, Cairns CB.
Division of Emergency Medicine, University of Colorado Health Sciences Center, Denver, USA.

STUDY OBJECTIVE: To determine whether the plateau phase of the expiratory capnogram (dco2/dt) can detect bronchospasm in adult asthma patients in the emergency department and to assess the correlation between dco2/dt and the peak expiratory flow rate (PEFR) in spontaneously breathing patients with asthma and in normal, healthy volunteers. METHODS: We carried out a prospective, blinded study in a university hospital ED. Twenty adults (12 women) with acute asthma and 28 normal adult volunteers (15 women) breathed through the sampling probe of an end-tidal CO2 monitor, and the expired CO2 waveform was recorded. The dco2/dt of the plateau (alveolar) phase for five consecutive regular expirations was measured and a mean value calculated for each patient. The best of three PEFRs was determined. The PEFR and dco2/dt were also recorded after treatment of the asthmatic patients with inhaled beta-agonists. RESULTS: The mean +/- SD PEFR of the asthmatic subjects was 274 +/- 96 L/minute (57% of the predicted value), whereas that of the normal volunteers was 527 +/- 96 L/minute (103% of the predicted value) (P < .001). The mean dco2/dt of the asthmatic subjects (.26 +/- .06) was significantly steeper than that of the normal volunteers (.13 +/- .06) (P < .001). The dco2/dt was correlated with PEFR (r = .84, P < .001). In 18 asthmatic subjects the pretreatment and posttreatment percent predicted PEFRS were 58% +/- 17% and 74% +/- 17%, respectively (P < .001), whereas the dco2/dt values were .27 +/- .05 and .19 +/- .07, respectively (P < .005). CONCLUSION: The dco2/dt is an effort-independent, rapid noninvasive measure that indicates significant bronchospasm in ED adult patients with asthma. The dco2/dt value is correlated with PEFR, an effort-dependent measure of airway obstruction. The change in dco2/dt with inhaled beta-agonists may be useful in monitoring the therapy of acute asthma.

ETCO2 and Mental Status

2001-01-01T09:22:00.000-08:00

Monitoring Mental Status

In an article in the October 2006 American Journal of Emergency Medicine, Noninvasive capnometry for continuous monitoring of mental status: a tale of 2 patients, authors Davis and Patel describe how capnography was used in the case of two similar unresponsive drug overdose patients to aid in the decision to intubate or not.

One patient with a stable ETCO2 was observed for three hours during which she eventually regained consciousness. The other patient had an initial ETCO2 of 33 that gradually rose to 41 over 45 minutes when the decision to intubate was made. That patient remained obtunded for three days.

The authors write: “In each of these cases of suspected overdose with nearly identical presentations, continuous noninvasive capnography was successfully used to monitor the depth of sedation and assist in the decision regarding intubation for airway protection. In the first case, the consistency in ETCO2 values correctly indicated a less severe overdose, with return to normal consciousness in the ED. In the second case, a gradual rise in ETCO2 suggested a decreasing level of consciousness despite the absence of a clear trend in GCS scores. The decision to perform intubation appeared to be justified by her prolonged obtundation...”

The bottom line of this case report is the suggestion that ETCO2 trending is a valuable indicator of the depth and direction of consciousness. While it has previously been used to monitor patients receiving medical sedation to prevent them from lapsing into hypoventilation, it can also be used to monitor EMS patients to gauge the depth and trend of their responsiveness.

ETCO2 and PaCO2 in Asthma

2001-01-01T09:21:00.000-08:00

Concordance between capnography and arterial blood gas measurements of carbon dioxide in acute asthma.

Corbo J, Bijur P, Lahn M, Gallagher EJ. Ann Emerg Med. 2005 Oct;46(4):323-7

In this study, 39 Patients, 37 Classified as “Severe Asthma,” received simultaneous measurements of arterial carbon dioxide and end-tidal carbon dioxide. The mean difference between Pa02 and PetCO2 was 1.0 mm Hg. The median Difference was 0 mm Hg. Only 2 patients were outside the 5 mg HG agreement (1-6, 1-12).

“In patients with acute, severe asthma exacerbations, we conclude that concordance between PetCo2 obtained by capnography and PaCo2 measured by arterial gas is high.”

Bottom Line for EMS: End tidal CO2 gives a good indication of the arterial blood gas level and can help a paramedic evaluate the severity of an asthmatic’s condition.

ETCO2 and Monitoring Sedated Patients

2001-01-01T09:06:00.000-08:00

The January 2007 issue of the Annals of Emergency Medicine has a number of articles about sedation, most notably a fine article by capnography seer Baruch Krauss called Capnography for Procedural Sedation and Analgesia in the Emergency Department. It is an excellent discussion of the utilty, literature and history of capnography to monitor for adverse respiratory events.

Also in the January issue is a study, Capnography and depth of sedation during propofol sedation in children, which again shows capnography"detects most airway and respiratory events leading to intervention before clinical examination or pulse oximetry."

Research Advances in Procedural Sedation and Analgesia by Dr. Steven Green, is an editorial from the same issue of Annals of Emergency Medicine.

Here are two brief excerpts:

"It now seems beyond reasonable dispute that most sedation-related airway and respiratory adverse events begin with abnormalities in ventilation that are detectable by capnography and then only latter evolve into the typical clinical manifestations of respiratory depression, apnea, or airway obstruction. Oxygen desaturation is often the last sign of complication. particuarly when supplemental oxygen has been administered..."

"The evidence suggests that supplemental oxygen cannot be considered mandatory during procedural sedation and analgesia and that the peril of disabling the warning capacity of pulse oximetry with this prophylaxis is real. Many readers will have already seen the obvious solution: the addition of capnography. Capnography accurately monitors ventilatory status regardless of supplemental oxygen administration and thus can serve as early warning for ventilatory compromise regardless of oxygen preference."

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Microstream capnography improves patient monitoring during moderate sedation: a randomized, controlled trial.

Pediatrics. 2006 Jun;117(6):e1170-8.

CONCLUSIONS: The results of this controlled effectiveness trial support routine use of microstream capnography to detect alveolar hypoventilation and reduce hypoxemia during procedural sedation in children. In addition, capnography allowed early detection of arterial oxygen desaturation because of alveolar hypoventilation in the presence of supplemental oxygen. The current standard of care for monitoring all patients receiving sedation relies overtly on pulse oximetry, which does not measure ventilation. Most medical societies and regulatory organizations consider moderate sedation to be safe but also acknowledge serious associated risks, including suboptimal ventilation, airway obstruction, apnea, hypoxemia, hypoxia, and cardiopulmonary arrest. The results of this controlled trial suggest that microstream capnography improves the current standard of care for monitoring sedated children by allowing early detection of respiratory compromise, prompting intervention to minimize hypoxemia. Integrating capnography into patient monitoring protocols may ultimately improve the safety of nonintubated patients receiving moderate sedation.

Bottom Line for EMS:

Capnography provides early warning of respiratory compromise.

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Supplemental oxygen impairs detection of hypoventilation by pulse oximetry.

Chest. 2004 Nov;126(5):1552-8.

CONCLUSION: Hypoventilation can be detected reliably by pulse oximetry only when patients breathe room air. In patients with spontaneous ventilation, supplemental oxygen often masked the ability to detect abnormalities in respiratory function in the PACU. Without the need for capnography and arterial blood gas analysis, pulse oximetry is a useful tool to assess ventilatory abnormalities, but only in the absence of supplemental inspired oxygen.

Bottom Line for EMS:

Without capnography, supplemental 02 can obscure impending respiratory problems.

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Does end-tidal carbon dioxide monitoring detect respiratory events prior to current sedation monitoring practices?

Burton JH, Harrah JD, Germann CA, Dillon DC. Acad Emerg Med. 2006 May;13(5):500-4.

This was a study of 60 patients undergoing sedation. There were abnormal findings in 36 encounters. 17 patients had acute respiratory events (apnea or hypoventilation). ETCO2 documented changes in 14 acute events before changes in SP02 or observed changes in respiratory rate.

“End-tidal carbon dioxide monitoring of patients undergoing PSA detected many clinically significant acute respiratory events before standard ED monitoring practice did so. The majority of acute respiratory events noted in this trial occurred before changes in SP02 or observed hypoventilation and apnea.”

Bottom Line for EMS: All sedated patients should receive ETCO2 monitoring instead of pulse oximetry alone.

ETCO2 and Cardiac Output

2001-01-01T09:04:00.000-08:00

Cardiac output and end-tidal carbon dioxide.

Weil MH, Bisera J, Trevino RP, Rackow EC, Crit Care Med. 1985 Nov;13(11):907-9.

In this study, 19 mini-pigs were put into v-fib and their ETCO2 and cardiac output were measured prearrest, during CPR, and at ROSC. During CPR, ETCO2 decreased 21%, Cardiac output decreased 33%. At ROSC, ETCO2 returned to baseline(after initially increasing 140%) and output returned to baseline. The authors concluded there is:

• “a high correlation between ETCO2 and cardiac output(pulmonary blood flow) during CPR.”
• “ETCO2 under conditions of constant ventilation, reflects the circulatory status of the animal during and after CPR.”
• “Reductions in ETCO2 during CPR are associated with comparable reductions in cardiac output.”
• “The extent to which resuscitation manuevers, especially precordial compression, maintain cardiac output may be more readily assessed by measurements of ETCO2 than palpation of arterial pulses.”

Bottom line for EMS: ETCO2 provides a measure of the effectiveness of CPR and cardiac output. An increase in ETCO2 during arrest often signals a return of spontaneous circulation.

End-tidal carbon dioxide as a noninvasive indicator of cardiac index during circulatory shock.

Jin X, Weil MH, Tang W, Povoas H, Pernat A, Xie J, Bisera J. Crit Care Med. 2000 Jul;28(7):2415-9

In this study 5 pigs had hemorrhagic shock induced by bleeding, 5 pigs had septic shock induced by infusion of e-coli, 6 pigs had cardiogenic shock induced by repeated episodes of v-fib. The PetCO2 was continuously measured. The results showed “Cardiac output and PetCO2 were highly related in diverse experimental models of circulatory shock in which cardiac output was reduced by >40 % of baseline values. Therefore, measurement of PetC02 is a noninvasive alternative for continuous assessment of cardiac output during low flow circulatory shock states of diverse causes.”

Bottom Line for EMS: A drop in ETCO2 may signal a drop in blood pressure for patient’s at risk for circulatory shock.

Expired carbon dioxide: a noninvasive monitor of cardiopulmonary resuscitation.

Gudipati CV, Weil MH, Bisera J, Deshmukh HG, Rackow EC. Circulation. 1988 Jan;77(1):234-9.

The authors put pigs into v-fib and monitored their ETCO2 during CPR. They wrote: “We conclude that ETCO2 provides a competent and technically simple, noninvasive monitor that highly correlates with cardiac output under conditions of constant ventilation during experimental CPR.”

Also of interest, they found: “Striking increases in ETCO2 levels that exceed prearrest values provide unequivocal evidence that spontaneous circulation has been restored such that precordial compression need not be interrupted to assess whether there has been a return of spontaneous circulation.”

Bottom Line for EMS: Instead of stopping CPR to routinely check for pulses, watch the ETCO2. If you see a sudden rise, stop and check for pulses then.

ETCO2 AS a Predictor of Rescusitation

2001-01-01T09:02:00.000-08:00

Utstein style analysis of out-of-hospital cardiac arrest-Bystander CPR and end expired carbon dioxide.

Grmec S, Krizmaric M, Mally S, Kozelj A, Spindler M, Lesnik B. Resuscitation. 2006 Dec 8

A new study has confirmed the prognosticative value of end-tidal carbon dioxide monitoring in cardiac arrest showing that ETCO2 values were higher at every point in time and in every analysis for patients who were resuscitated that those who weren’t. It also reported that “in 81% of patient who had ROSC a rise in ETCO2 was the first evidence of ROSC, before a palpable pulse or measurable blood pressure was established.” No one was resuscitated who had an initial ETCO2 lower than 1.33kP (9.965 mmHG).

Conducted in Slovenia from January 2001 to December 2004, the study used an Utstein style analysis to investigate the effects of various factors on survival, including end tidal carbon dioxide. An Utstien style analysis uses a recognized template for reporting data from resuscitation studies that ensures comparability. The study found that “arrival time, witnessed arrest, bystander CPR, initial ETCO2, final ETCO2 were significantly positively related with ROSC on admission and with survival. They suggest that initial ETCO2 should be included in every Utstein style analysis.

The study observed 592 out of hospital cardiac arrests. Of that group, resuscitation was attempted on 389, which formed the study enrollment. 195 (50%) had ROSC and 82 (21%) were discharged from the hospital. ETCO2 was measured every minute during the resuscitation using a Life pack 12 beginning with the first post intubation reading

The initial ETCO2 of patients with ROSC on admission to the hospital was 18mmHG versus for 6.75 for those without ROSC. The initial value was 19.5 for those who survived versus 11 for those who did not.

The final ETCO2 values of patients with ROSC on admission was 26 mm HG versus 7.5 for those without ROSC. And the final value was 29.25 in those who survived versus 14.25 for those who died.

All patients with ROSC had an initial value of at least 9.965.

When patients had a ROSC, their ETCO2 rose by an average of 13.5mmHG before a palpable pulse or BP was detected.

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Here's some info on Utstein style anaylsis:

Recommended Guidelines for Uniform Reporting of Data From Out-of-Hospital Cardiac Arrest: The Utstein Style

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End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest.

Levine RL, Wayne MA, Miller CC. N Engl J Med. 1997 Jul 31;337(5):301-6.

End tidal CO2 monitoring can confirm the futility of resuscitation according to this study.

The authors studied 150 prehospital cardiac arrests where the patients were in pulseless electrical activity(PEA). V-fib, v-tack and persistent asystole were excluded as well as patients with hypothermia, trauma, poisioning, hypovolemia, cardiac tamponade, and tension pnemothorax. The group did include post defib patients with electrical activity but no pulse.

There were 115 nonsurvivors and 35 survivors to hospital admission. The initial ETCO2 on intubation were: Nonsurvivors 2-50, Survivors 5-22. After 20 minutes of CPR, the ETCO2 were: Nonsurvivors 0-10, Survivors 18-58.

The authors wrote: “No patient who had an end-tidal carbon dioxide of level of less than 10 mm HG survived. Conversely, in all 35 patients in whom spontaneous circulation was restored, end-tidal carbon dioxide rose to at least 18 mm Hg before the clinically detectable return of vital signs...The difference between survivors and nonsurvivors in 20 minute end-tidal carbon dioxide levels is dramatic and obvious.”

"An end-tidal carbon dioxide level of 10 mmHg or less measured 20 minutes after the initiation of advanced cardiac life support accurately predicts death in patients with cardiac arrest associated with electrical activity but no pulse. Cardiopulmonary resuscitation may reasonably be terminated in such patients.”

Bottom line for EMS: ETCO2 levels after twenty minutes of rescusitation can be used to help make the decision to terminate the rescusitation.

Can cardiac sonography and capnography be used independently and in combination to predict resuscitation outcomes?

Salen P, O'Connor R, Sierzenski P, Passarello B, Pancu D, Melanson S, Arcona S, Reed J, Heller M; Acad Emerg Med. 2001 Jun;8(6):610-5

In this study to To measure the ability of cardiac sonography and capnography to predict survival of cardiac arrest patients in emergency departments, the authors, the authors enrolled one hundred and two patients in cardiac arrest. All patients had cardiac sonography. 53 also had ETCO2 monitoring. Of the two diagnostic tests, only capnography was a significant predictor of survival.

“An ETCO2 value of 16 torr or less successfully discriminated between the survivors and the nonsurvivors in our study because no patient survived with an ETCO2 less than 16 torr. Our logistic regression model further showed that for every increase of 1 torr in ETCO2, the odds of surviving increased by 16%.”

The authors concluded: “Capnography is an outstanding predictor of survival.”

Bottom line for EMS: The higher the initial ETCO2 level, the greater the likelihood of survival. No matter what the patient may look like or the history, a high ETCO2 should ensure the best efforts of EMS to try to achieve resuscitation.

Prediction of outcome of cardiopulmonary resuscitation from end-tidal carbon dioxide concentration.

Callaham M, Barton C. Crit Care Med. 1990 Apr;18(4):358-62.

In this study of 55 nontraumatic arrests, there were 14 resuscitations. The study included patients in v-fib, EMD and asystole. Patients who developed pulse had mean initial ETCO2 of 19, those who did not had mean initial ETCO2 of 5. An initial ETCO2 of 15 correctly predicted eventual ROSC with a sensitivity of 71%, and a specificity of 98%, a positive predictive value of 91%.

“The initial PETCO2, obtained as soon as intubation was accomplished, was highly predictive of whether spontaneous pulse would be restored at any time during resuscitation.”

A key finding in the study however showed that 4 patients who developed a pulse had initial ETCO2 less than 10 mm Hg.

Bottom line for EMS: Don't give up on anyone just because their initial ETCO2 is low. Still the higher the initial reading, the better the chance of successful resuscitation.

Ventilating Head Injury

2001-01-01T01:15:00.000-08:00

The use of quantitative end-tidal capnometry to avoid inadvertent severe hyperventilation in patients with head injury after paramedic rapid sequence intubation.

Davis DP, Dunford JV, Ochs M, Park K, Hoyt DB.J Trauma. 2004 Apr;56(4):808-14

In this study of 291 intubated head injured patients, 144 had ETCO2 monitoring. The patients with ETCO2 monitoring had lower incidence of inadvertant severe hyperventilation (5.6%) than those without ETCO2 monitoring (13.4%). Patients in both groups with severe hyperventilation had significantly higher mortality (56%) than those without (30%).

“The use of ETCO2 monitoring to guide ventilation for patients with severe head injury undergoing paramedic RSI appears to prevent excessive hyperventilation.”

Bottom Line for EMS: Monitor ETCO2 to prevent hyperventilation in intubated head injured patients.

Misplaced Tubes

2001-01-01T01:00:00.000-08:00

Misplaced Tubes

The effectiveness of out-of-hospital use of continuous end-tidal carbon dioxide monitoring on the rate of unrecognized misplaced intubation within a regional emergency medical services system.

Silvestri S, Ralls GA, Krauss B, Thundiyil J, Rothrock SG, Senn A, Carter E, Falk J. Annals of Emergency Medicine, May 2005, pgs 497-503l

If there ever was an argument for requiring continuous ETCO2 monitoring on all intubations, this is it. Over a ten month period, in 11 counties in Florida there were 153 intubations. 93 (61%) used continuous ETCO2 Monitoring. 60 (39%) did not. Upon arrival at the Emergency department there were 14 (9%) unrecognized misplaced intubations. There were 0 (0%) misplaced tubes in the group that used continuous ETCO2 monitoring. There were 14 (23%) in unmonitored group.

The authors wrote: “The unobserved unrecognized misplaced intubation risk difference is compelling. This study demonstrates that it is possible to attain a zero unrecognized misplaced intubation rate.”

Four years earlier, another study was done in Florida that showed during an 8 month period out of 108 “intubated” patients brought to a large Florida ED, there were 27 misplaced tubes (27%) on arrival at ED. 18 were in the esophagus, 9 in hypopharanx. 17 of 18 esophageal intubations had an absence of expired CO2, the one with CO2 was nasally intubated and breathing their own. 4 of 9 hyphopharengal intubations had an absence of expired CO2.
- Katz SH, Falk JL, Misplaced endotracheal tubes by paramedics in an urban emergency medical services system, Annals of Emergency Medicine, January 2001

The authors wrote: “The incidence of out-of-hospital, unrecognized, misplaced endotracheal tubes in our community is excessively high and may be reflective of the incidence occuring in other communities...Functionally, whether the tubes were misplaced initially or dislodged en route to the hospital makes little difference to the patient....Despite written protocols requiring the out-of-hospital use of ETCO2 devices in our community, we...found their use to be sporadic... We believe that routine use of this technique, both at the time of intubation and as an ongoing monitor during transport, could potentially eliminate the problem of unrecognized misplaced ETT placement....”

Bottom Line: Intubated patients should all have continuous ETCO2 monitoring.

ETCO2 To Differentiate Cause of Arrest

2000-01-01T01:01:00.000-08:00

Here is a fascinating 2003 study about the differences in initial ETCO2 readings between respiratory cardiac arrest versus vfib/vt arrests.

Difference in end-tidal CO2 between asphyxia cardiac arrest and ventricular fibrillation/pulseless ventricular tachycardia cardiac arrest in the prehospital setting.

The researchers analyzed 44 patients with respiratory cardiac arrest (asthma, hanging, obstructed airway, aspiration, etc.) and 141 with primary cardiac arrest, measuring their ETCO2 at intubation and then every minute.

They discovered that patients in respiratory induced cardiac arrest had a significantly higher initial ETCO2 than patients in primary cardiac arrest, but that the high initial reading was not prognostic for ROSC.

But after a minute, during which the respiratory numbers invariably came down, the minute numbers were prognostic for ROSC.

In the vfib/vt group initial, 1 minute and subsequent ETCO2 were prognostic for ROSC.

In all patients who achieved ROSC, no patient had an initial ETCO2 lower than 10 mmHg.

The authors write “during the period of asphyxia, continued cardiac output prior to cardiac arrest permits continued delivery of CO2 to the lungs, which (in the absence of exhalation) results in higher alveolar C02 when ventilation is resumed.”

The bottom line then is that initial ETCO2 readings can help provide clues into the causes of cardiac arrest, and help direct treatment. For instance, a patient with an extremely high initial reading likely had a hypoxic cause of arrest, and positive pressure ventilation will be a priority.

Here are numbers from the study:

Asphyxia Arrest Initial readings

ROSC = 70.1 Without ROSC = 62.8

VFIB/VT Initial Readings

ROSC = 20.3 Without = 8.2

Asphyxia Arrest After 1 minute

ROSC = 35.8 Without 19.4

VFIB/VT After 1 minute

ROSC = 30.2 Without = 14.2

Asphyxia Final

ROSC = 31.2 Without = 7.2

VFIB/VT Final

ROSC = 28.1 Without = 6.2