Tissue oxygen saturation vasoocclusive testing. The initial slope, occlusion slope and recovery slopes are shown. During the initial phase, the tissue oxygen saturation (StO2) level is monitored over time (initial). At occlusion, the tourniquet is programmed to insufflate a cuff to 50 mmHg above the patient's systolic blood pressure. The StO2 level is then monitored during the ischemic period to calculate the steady-state ischemic downslope (ischemic slope). This is postulated to represent a combination of oxygen content in the microcirculation and the metabolic demand of the tissues. Next the cuff is released so that blood flow may be reestablished. The tissue is then reperfused, with the rate representing the capacity to autoregulate and reperfuse the tissue exposed to regional ischemia (recovery slope). A patient with intact endothelial cell function, microcirculation and oxygenation capacity will reperfuse quickly, yielding a steep recovery slope, while patients in whom these mechanisms are impaired will have a shallower recovery slope.