Expired PCO₂ as a prognostic indicator of successful resuscitation from cardiac arrest

We performed a study to determine if the measurement of expired PCO₂ during CPR for cardiac arrest could be used as a prognostic indicator of successful resuscitation. Twelve mongrel dogs were fibrillated electrically, and external chest massage and assisted ventilation were applied for 15 minutes. Expired PCO₂ and aortic and right atrial pressures were monitored each minute of arrest. Coronary perfusion pressure (CPP) was calculated by subtracting the right atrial from the aortic diastolic pressure. Half the dogs received high-force chest compression (801b) and half received low-force chest compression (401b). The six dogs that received high-force compression were resuscitated successfully. The expired PCO₂ was significantly higher in the successfully resuscitated dogs (expired PCO₂ = 9.6 ± 3.2 mm Hg) when compared to those dogs that died (expired PCO₂ = 3.2 ± 1.1 mm Hg, P < .01). Expired PCO₂ was highly correlated (r = 0.91, P < .01) with the CPPs. The measurement of expired PCO₂ during attempted CPR may be useful as a noninvasive indicator of CPP and adequate technique. Further studies on the use of this technique as an assessment criterion are warranted.