An apparatus and method for resuscitating a patient suffering from cardiac arrest or another condition in which normal circulation has been interrupted. A ventilator is used for delivering a gas mixture to the patient. The ventilator is configured to adjust the partial pressure of CO2 to one or more partial pressures high enough to slow expiration of CO2 from the patient's lungs and thereby maintain a reduced pH in the patient's tissues for a period of time following return of spontaneous circulation.