Episode 39: End Tidal CO2 Application and Limitations in Prolonged Field Care
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) that will increase ICP.
Once you listen to Doug and Dennis talk about ETCO2, check out the EMCrit episode below for the ED perspective.
Disclosure: We do not promote any one piece of equipment or manufacturer and have no financial interests. Pictures are meant to display capability only.
ETCO2 as a monitoring technology is often misunderstood.
My notes from the EMCrit episode:
-paCO2 is at least the same as ETCO2 but likely be higher
-Prognostic for poor outcome after 20 mins of CPR if capnograph stays below <10mmHg
-ETCO2 monitoring is law in ORs
-Supplemental O2 requires ETCO2 because it distorts pulse oximetry
If you really want to dig into capnography visit http://www.capnography.com