Capnography

[AnthonyM83]

As far as the cardiac arrest I mentioned, the medic kept making repeated intubation attempts, failing and telling EMTs to hold off on CPR so that he could try again. At two points, we spent almost a minute each time confirming lung sounds by two medics each time.

In addition to the difficulty in intubating, I think he said his waveform wasn't right, but the number was around 35-40 and there was condensation and color change....I THINK. Doc confirmed placement at ER (Medics have to get their PCR signed off on that).

Then it took forever to get patient loaded, because FF's would stop doing CPR to get the straps ready, so I would take over, but when I stopped to get straps on my side and asked them to continue for me, they wouldn't...so I'd stop the straps and keep compressions going. This woman had pulses come and go, too, so she actually had a bit of a chance....(of course they never documented that we kept getting and losing pulses...) Sigh

[chbare]

Tube condensation is very unreliable. Also remember high or low ETCO2 readings may be expected depending on the situation. For example, a DKA patient will have a low CO2 r/t compensation for the metabolic acidosis. Attempting to "normalize" the CO2 could be met with disastrous results.

Take care,

chbare.

[AZCEP]

As long as ventilations remain the same, you can estimate cardiac output or more correctly pulmonary perfusion with capnography as well. It won't give you any hard/fast values to use, but it is a pretty reliable estimate of how well your managing the situation.

[AnthonyM83]

Oh, follow-up:

So, when the number isn't between 35 and 45, you modify your ventilations so that it stays within it, right? Even if it goes beyond 10-12/min, right...how far off do they need to be before you assume it's not a problem with your ventilations rather with them.

(BTW, thought I'd share I had a dream last night where I was tracking the capnography wave...least I remembered all this stuff in my sleep!)

[AZCEP]

As has been already mentioned, because capnography has a +/- of 5 mmHg, I tend to use a range of 30-50 mmHg to maintain. If the range is beyond that consider using other tools to make a decision. Adding information to the equation can help considerably.

Is the SpO2 staying where it should be? Is the ECG staying about the same? What are the other vitals doing at the same time? Capnography is highly sensitive, but it does not tell you everything about what is happening.

[chbare]

Not always. See the DKA example above. I have even seen patients who do better with elevated CO2 levels. Permissive Hypercapnea. Much will depend on the patients condition, hemodynamic status, metabolism, and gas exchange. Also know that changes in CO2 will change our acid/base environment and cause electrolyte shifts. Post code with ROSC, you may have not have labs or additional information, so yeah, you may end up shooting for the magic numbers. Also remember, changes in condition will cause increased or decreased CO2 production. Changes in status will even change the ETCO2 to PCO2 gradient. Complicated enough to make your head spin.

Take care,

chbare.

[VentMedic]

That 35 - 45 is only a NORMAL value. Different patients may have some variance from that depending on what their normal PaCO2 is, lung pathology and acute disease process. Secretions, pulmonary edema, poor perfusion and a whole list of things that skew that number. We give that just for a decent reference point and an easy number for paramedics who do not have a starting reference or some idea about what is going on with the patient's overall clinical picture.

Biggest pet peeve is when "well meaning" CCT Paramedics 'make' IFT ventilator patients NORMAL by screwing with the ventilator settings thinking they are doing us a favor "because the number wasn't between 35 - 45".

Watch the links and learn more about V/Q mismatch and shunting.

The other problems is unfamiliarity with the equipment. Poor calibration, maintenance, cracks in lines, cracks in the sensor, malfunctioning sensor, poor connections etc.

Just like the pulse ox, there's always the human factor of both the provider and the patient to be aware of.

[AnthonyM83]

Should there be a difference in CO2 level per exhalation between cardiac arrests and respiratory arrests...since one is assumed to have a lower metabolic rate? So to keep number between 35-45 one would expect to bag a faster rate for respiratory arrest?

[AnthonyM83]

Just reading through the posted links.

It says you may be able to time epi doses based on the .3 torr drop after each round...are most of your monitors that specific that you can notice a .3 drop? Aren't the numbers constantly changing by one digit all the time...would a drop of .3 in the field during CPR really be an indicator?

I do like that idea that it can be an indicator of CPR quality, though...!

[Spock]

Lots of good comments here and it is good to see so many people are knowledgeable on this topic. I read the comments and would just add a few things. If I am repeating what somebody already wrote I apologize.

Capnography is a valuable monitor but it is only one of many we use. The most important monitor is a good physical exam and a vigilant health care provider. Correlate the ETCO2 reading with everything else you do and see.

Capnography will be the first monitor to show the patient either lost or regained a pulse. I use the ETCO2 as a guide for whoever is doing compressions. If it goes up then compressions are effective. Also, my experience shows if we start working a code and the first ETCO2 is single digits after intubation I know we have no chance of regaining pulses and I will stop the resuscitation. We have that ability here to call the code in the field. Medical command has always supported that and families are receptive when it is explained to them properly. There is some literature to support this but I'm not at home so I can't cite the reference.

Don't forget there is a place for capnography in the non-intubated patient. It will show if your treatments are helping or not. I wrote the SOP's for my service on this and we require both SPO2 and capnography for any patient that is getting fentanyl for pain management. Capnography is your first monitor to show hypoventilation. Of course you should look at the patient first but ETCO2 is valuable in this setting.

I agree the Easycaps are a poor substitute and I never use them in the field. Direct visualization is a poor means to confirm tube placement because I can't count the times a medics swears he say tube go in the trachea when it is in the goose. I believe the tube is being pulled out when the stylet is removed because medics around here don't continue visualization while somebody else pulls the stylet. Also, stylets come out more easily if they are lubricated.

We've been using capnography for almost 7 years and our medics really like it. This is one piece of technology where prehospital is ahead of the hospital. Most of our ER's still don't have capnography and the staff are painfully uneducated on the subject. What a shame.

Live long and prosper.

Spock