Does Hypoxia or Hypercarbia Independently Affect Resuscitation From Cardiac Arrest?

In a previous cardiopulmonary resuscitation (CPR) study in swine, ventilation was associated with improved rate of return of spontaneous circulation (ROSC) compared with nonventilated animals, which had greater hypoxia and hypercarbic acidosis. We used the same model to determine the independent effect of hypoxia and hypercarbic acidosis on ROSC after cardiac arrest. Laboratory model of cardiac arrest. University teaching hospital laboratory. Domestic swine (23 to 61 kg). Twenty-four swine were randomly assigned to three groups receiving ventilation during CPR with 85% O2/15% N2 (control), 95% O2/5% CO2 (hypercarbia), or 10% O2/90% N2 (hypoxia). All animals had ventricular fibrillation for 6 min without CPR, then CPR with one of the ventilation gases for 10 min, then defibrillation. Animals without ROSC received epinephrine, 85% O2, CPR for another 3 min, and defibrillation. During the tenth minute of CPR, the hypercarbic group had more mean (SD) arterial hypercarbia than the control group (Pco2, 47±6, compared with 34 ±6; p