For many years, the administration of supplemental oxygen has been considered beneficial for the treatment of patients with acute myocardial infarction largely based on experimental laboratory data. For example, in a laboratory study, anaesthetised dogs underwent coronary artery occlusion and were then administered either 21% oxygen, 40% oxygen or 100% oxygen. In the 40% oxygen group, there was decreased myocardial injury and infarct size compared with the air or 100% oxygen groups[7].