Differences in the strategies and potentials of human adaptation to hypoxia

The general patterns and individual specific features of human adaptation to acute hypoxic hypoxia caused by breathing a hypoxic oxygen-nitrogen gas mixture containing 8.0% oxygen have been studied. It was found that, at the initial stage of hypoxia, all examined subjects demonstrated a reduced oxygen consumption as compared to normoxia; then, this parameter increased and, beginning from a certain moment (after 5-15 min of exposure), exceeded the baseline level by 10-40%. Hypotheses explaining the mechanisms of this growth in oxygen consumption during hypoxia are considered. It has been found that the roles of the cardiovascular system and mechanisms of the tissue and cellular utilization of oxygen in the growth of the rate of oxygen consumption caused by hypoxia vary in different subjects. The hypothesis is put forward that the relatively low potential for rearrangement of the biological oxidation system at the cellular level, aimed at increasing the rate of oxygen consumption, predetermines a need to increase the rate of oxygen supply by the blood and, therefore, a greater strain of the cardiovascular system. In many cases, this strain can cause failure of adaptation to hypoxia. Other parameters that can serve as characteristics of a subject's resistance to hypoxia, such as the intensity of EEG slow waves and the level of blood oxygenation, are also considered. © Pleiades Publishing, Inc. 2007.