It is important to understand that the majority of microcirculatory damage from ischemia occurs during the first 3 to 4 hours or reperfusion and, to a lesser degree, over the next 24 to 48 hours. Therefore, early recognition and treatment become critical. We are currently using HBO treat most patients with revascularized or replanted extremities, and ischemia time greater than 6 hours. We are also treating patients who experience the occasional free muscle.