Prolonged Field Care 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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