ObjectivesTo compare the initial end-tidal CO2(PetCO2) during cardiopulmonary resuscitation in asphyxial versus ventricular fibrillatory cardiac arrest.DesignA cohort study.SettingUniversity research laboratory.SubjectsForty domestic piglets.InterventionsAsphyxial cardiac arrest was produced by clamping the endotracheal tube in 20 piglets and was continued for 10 minutes after loss of aortic pulsations occurred. Ventricular fibrillation (VF) was induced by applying 60 Hz of alternating current via a pacing wire to the myocardium of the other 20 piglets, and continued for a 15-minute downtime. Cardiopulmonary resuscitation (CPR) was then provided to each group for two minutes, followed by standard advanced cardiac life support protocols.Measurements and main resultsAll piglets were instrumented for continuous monitoring of PetCO2, electrocardiogram, central venous pressure, and aortic pressure, PetCO2of the first breath of CPR was 91 plusmn; 20 mmHg in the asphyxial group versus 34 plusmn; 14 mmHg in the VF group (P 0.001). The asphyxial group continued to exhibit significantly greater PetCO2for the first five breaths of resuscitation, after which there were no differences. The coronary perfusion pressures during the first breaths of CPR did not differ between the two groups. High initial PetCO2did not correlate with return of spontaneous circulation.ConclusionsEnd-tidal CO2during the first five breaths of CPR is much higher after an asphyxial cardiac arrest than VF. In each case, the initial PetCO2appears to reflect alveolar CO2prior to CPR. After one minute of CPR, PetCO2is useful in monitoring the effectiveness of CPR.
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