Abstract
the arterial hypdxemia that occurs in all subjects acutely exposed to high altitude lessens over succeeding days and weeks through ventilatory acclimatization (2). If acclimatization proceeds normally, the partial pressure of oxygen (Po 2) in arterial blood increases over time. If acute mountain sickness (AMS) intervenes and becomes severe, however, acclimatization does not occur and arterial oxygenation worsens (9). There have been many studies on the effect of ventilatory acclimatization, but these have been concerned primarily with the awake state. At altitude the arterial oxygenation is worse during sleep than during the awake state (10, 11, 13), and the degree of hypoxemia during sleep is probably important in determining the ability to acclimatize. Furthermore sleep hypoxemia might be expected to improve as part of the ventilatory acclimatization. However, we did not find such increases in arterial oxygen saturation during sleep in a cross-sectional study comparing groups of subjects who had been at altitude (5,360 m) for varying lengths of time and therefore had different degrees of acclimatization (5, 10). We wondered if any lack of improvement in arterial oxygen saturation with acclimatization had been obscured by the wide ranges in sleep. arterial oxygen saturation observed in all groups. Therefore the present longitudinal study, designed to examine the effects of acclimatization on sleep hypoxemia, uses each subject as his or her own control to eliminate differences between individuals.
Published Version
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