Hyperbaric oxygen (HBO) was first used by placing a patient with the “bends” in a pressure chamber and increasing the pressure to 3 atm with 100% oxygen. It was soon accepted for the treatment of decompression sickness, CO intoxication, chronic non-healing wounds, and infected ischemic extremities. A decrease in reperfusion injury led to some work in 1997 on acute myocardial infarction. Varied cardiovascular changes reported are changes in heart rate, blood pressure, and cardiac output during HBOT. The hemodynamic and microcirculatory effects of HBO appear to be effective in compensating ischemic conditions, particularly in cases of heterogeneous microcirculatory hypoperfusion.