ETCO2 and PaCO2 in Asthma

Concordance between capnography and arterial blood gas measurements of carbon dioxide in acute asthma.

Corbo J, Bijur P, Lahn M, Gallagher EJ. Ann Emerg Med. 2005 Oct;46(4):323-7

In this study, 39 Patients, 37 Classified as “Severe Asthma,” received simultaneous measurements of arterial carbon dioxide and end-tidal carbon dioxide. The mean difference between Pa02 and PetCO2 was 1.0 mm Hg. The median Difference was 0 mm Hg. Only 2 patients were outside the 5 mg HG agreement (1-6, 1-12).

“In patients with acute, severe asthma exacerbations, we conclude that concordance between PetCo2 obtained by capnography and PaCo2 measured by arterial gas is high.”

Bottom Line for EMS: End tidal CO2 gives a good indication of the arterial blood gas level and can help a paramedic evaluate the severity of an asthmatic’s condition.