September Log

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.