As a model of human hypoxia, exposure to high altitude causes a number of ventilatory, circulatory and hemopoietic adaptations. A review of the literature on blood gas transport responses to hypoxia indicates that they are influenced not only by altitude, but also by factors related to acclimatization. In addition, it appears that the need to oxygenate tissues conflicts with the need to maintain H+ homeostasis. Thus, the final situation represents a compromise between the respiratory adjustment aimed at increasing blood alkalosis in order to optimize the oxygen transport system, and the metabolic readjustment aimed at reestablishing normal blood pH. There are factors like red cell 2,3-diphosphoglycerate, a compound that decreases the hemoglobin affinity for oxygen, that can influence that balance by affecting arterial oxygen saturation through mechanisms independent of respiration.