The arterial saturation of hemoglobin is dependent upon the arterial PO2, PCO2, and pH (see Chap. 10). A low PCO2 and a high pH cause the oxygen hemoglobin curve to shift to the left so that hemoglobin is more saturated under these conditions than under normal conditions. A person who can ventilate great volumes in response to hypoxia can exhale more CO2 and cause the pH to become elevated. It has been shown that those who successfully deal with altitude have strong hypoxic ventilator drives, allowing them to have a higher arterial PO2 and oxygen saturation (118). In fact, when alveolar PCO2 values were obtained at the top of Mount Everest in the 1981 expedition, the climbers had values much lower than expected (140). This ability to hyperventilate, coupled with the barometric pressure being higher than expected, resulted in higher arterial PO2 and, of course, VO2 max values. How high must your VO2 max be to climb Mount Everest?