Recycled Prolonged Fieldcare Podcast 39: ETCO2 Applications and Limitations

Upgrading your airway kit with a portable end tidal CO2 monitor can help in a couple situations. While it has its limitations, it is essential for quickly determining if your tube is in the trachea during an intubation. This can be accomplished most accurately via a device with a quantitative waveform such as the Emma Capnograph. If you can’t get your hands on an Emma, the qualitative colormetric device that changes color when exposed to acid in the exhalations. False positives can occur due to other acids in the airway such as vomitus or even if the patient has recently had a carbonated beverage. While those are rare, you should be aware of the possibility. Having a visual indication of tube placement can be extremely helpful during loud transports such as on aircraft.

Another time that ETCO2 monitoring is very useful is during CPR. There will likely be a very low reading despite high quality CPR. If the heart begins to beat spontaneously, you should see an immediate increase of the numbers on the display of your device. ETCO2 can also be used as a prognostic indicator. If the ETCO2 remains below 10mmHg for 20 mins of CPR this may indicate that the patient has a very poor prognosis. After you listen to our podcast, Check out Scott Weingart’s EMCrit podcast on the subjects to hear his thoughts on this.

ETCO2 is also useful the intubated TBI patient. Per our clinical practice guideline, ETCO2 in a patient with moderate to severe TBI should be kept between 35-40mmHg. In a patient with herniation, you can temporarily increase ventilators rate in order to vasoconstrict the blood vessels in the brain, thus reducing swelling. This can only be done for a short time because hyperventilation worsens cerebral ischemia. Also avoid hypoventilation (EtCO2 45mmHg or more) that will increase ICP.

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