Tuesday, March 10, 2009

Tuesday March 10, 2009
A note on end-tidal carbon dioxide (ETCO2) during CPR

Expired carbon dioxide is a reliable measure of pulmonary perfusion and thus cardiac output (if ventilation is held constant) because carbon dioxide is excreted by the blood into the lungs. Carbon dioxide is easily measured with a portable capnometer placed between the end of an endotracheal tube and a resuscitation bag.

Several studies have shown the correlations between ETCO2 and cardiac output and myocardial perfusion pressure, implying that continuous measurement may gauge the effectiveness of ongoing CPR. Patients with higher ETCO2 partial pressures during CPR has higher chances of ROSC (return of spontaneous circulation). Atleast ETCO2 partial pressure of 10 mm Hg (or greater) is a predictor of survival - preferably 15 or more mm Hg.

Levine et al prospectively measured ETCO2 in 150 consecutive victims of cardiac arrest outside the hospital. The sensitivity, specificity, positive predictive value, and negative predictive value of a 20-minute ETCO2 level of less than10 mm Hg were all 100%
2.




References:

1. Sanders AB, Kem KB, Otto CW, Milander MM, Ewy GA. End-tidal carbon dioxide monitoring during cardiopulmonary resuscitation. A prognostic indicator for survival. JAMA 1989;262:1347-51.

2. Levine RL, Wayne MA, Miller CC. End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest. N Engl J Med 1997; 337:301-6.


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