Red cell function on Mount Everest

Blood P50, 2,3-DPG and acid-base status were studied in 20 Westerners during the American Medical Research Expedition to Everest. In vivo P50 was maintained on a narrow range (27.6-28.1 Torr) up to 6300 m because of the opposing effects of 2,3-DPG and respiratory alkalosis. At extreme altitute, the P50 decreased (18.5 Torr on the summit) due to the stronger effect of uncompensated respiratory alkalosis (pH 7.78). The net result was a preservation of arterial saturation in spite of falling PO2.