Red cell metabolism and oxygen affinity of healthy individuals during exposure to high altitude.

Abstract

In man adaptation of oxygen transport to low ambient pO2 comprises a series of physiological responses, including increases in ventilation, cardiac output, and oxygen carrying capacity (hemoglobin concentration). The increase in ventilation is generally considered to be the most responsive and effective of these. A fourth adaptive mechanism which involves changes in oxygen affinity of circulating red cells has been focused on recently (Astrup et al, 1968; Lenfant et al, 1968). Theoretically, a decrease in red cell affinity for oxygen will facilitate oxygenation of the tissues and an increased amount of oxygen will be released from the red cells at a given pO2. However, oxygen uptake by the red cells in the lungs may be impaired. A decrease in red cell affinity for oxygen is beneficial for the total oxygen transport only when the arterial oxygen saturation is greater than 70%.