Effect of Repeated Normobaric Hypoxia Exposures during Sleep on Acute Mountain Sickness, Exercise Performance, and Sleep during Exposure to Terrestrial Altitude

摘要

There is an expectation that repeated daily exposures to normobaric hypoxia (NH) will induce ventilatory acclimatization (VEacc) and be effective for lessening acute mountain sickness (AMS) and the exercise performance decrement during subsequent hypobaric hypoxia (HH) exposure. However, this notion has not been tested objectively. Healthy, unacclimatized sea level (SL) residents slept for 7.5 hrs each night for 7 consecutive nights in hypoxia rooms under either NH (n=14, 24+/-5 yr; mean+/-SD) or 'sham' (n=9, 25+/-6 yr) conditions. The ambient %O2 for the NH group was progressively reduced by 0.3%O2 (150 meters equivalent) each night from 16.2%O2 (2200 m eq) on the 1st night to 14.4%O2 (3100 m eq) on the 7th night, while that for the ventilatory and exercise-matched sham group remained at 20.9%O2. Beginning 25 hrs post-sham or NH treatment all ascended and lived for 5 days at HH (4300 m). Partial pressure of end-tidal CO2 (PetCO2), oxygen saturation (SaO2), AMS, and heart rate (HR) were measured repeatedly during daytime rest, sleep or exercise (11.3 km treadmill time trial (TT)).