August Capnography Log

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.


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.


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.


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.


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.


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.


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