Capnography for Paramedics: January 07 Log

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.

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