Effect of Repeated Normobaric Hypoxia Exposures During Sleep on AcuteMountain Sickness, Exercise Performance, and Sleep During Exposure toTerrestrial

http://www.dtic.mil/dtic/tr/fulltext/u2/a545957.pdf


Effect of Repeated Normobaric Hypoxia Exposures During Sleep on Acute
Mountain Sickness, Exercise Performance, and Sleep During Exposure to
Terrestrial Altitude
C.S. Fulco, S.R. Muza, B.A. Beidleman, R. Demes, J.E. Staab, J.E. Jones, A.
Cymerman


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)). From pre-to post-treatment at SL, resting PetCO2 decreased (p<0.01) for the NH group (39±3 to 35±3 mmHg) but not for the sham group (39±2 to 38±3 mmHg). Throughout HH, only sleep SaO2 was higher (80±1% vs 76±1%, P<0.05) and only AMS upon awakening was lower (0.34±0.12 vs 0.83±0.14,
Ventilatory acclimatization, AMS, physical performance, hypobaric hypoxia, arterial oxygen saturation, SaO2
Charles S. Fulco, Stephen R. Muza, Beth A. Beidleman, Robby Demes, Janet E. Staab, Juli E. Jones, and Allen Cymerman