The purpose of the study was to test the hypothesis that intracoronary aqueous oxygen (AO) hyperbaric reperfusion reduces myocardial injury after prolonged coronary occlusion. Background. Attenuation of ischemia/reperfusion injury by the use of hyperbaric oxygen (HBO) administered during reperfusion has been demonstrated for a wide variety of tissues, including myocardium. We have recently developed a more practical, catheter-based, site-specific method for delivery of oxygen at hyperbaric levels with aqueous oxygen infusion.