Altitude Threshold for Sleep Disturbances During Exposure to Acute Hypobaric Hypoxia

Abstract

To determine the altitude threshold for sleep disturbances during exposure to hypobaric hypoxia, 43 sea‐level (SL) residents (mean±SD, 22±4 yr) completed a one night sleep assessment at SL and during exposure to one of six levels of hypobaric hyoxia (2000 m (N=4), 3000 m (N=5), 3500 m (N=8), 4000 m (N=9), 4300 m (N=12), or 4500 m (N=5)). Each wore a pulse oximeter to measure arterial oxygen saturation (SaO2) and desaturation events (# of > 6% drops in SaO2 for ≥ 8 sec) and a wrist motion detector to estimate sleep quality (awakenings/hr) and quantity (% sleep). Mean sleep SaO2 (%) decreased (P<0.05) from SL (96±1) to 2000 m (92±1), 3000 m (89±2), 3500 m (83±4), 4000 m (73±4), 4300 m (72±4) and 4500 m (71±4). Desaturation events/hr did not increase from SL (0±1) at 2000 m (1±12), 3000 m (12±34) or 3500 m (5±4) but increased (P<0.05) at 4000 m (34±48), 4300 m (56±50) and 4500 m (117±17). Awakenings/hr did not increase from SL (1±1) at 2000 m (1±2), 3000 m (2±2) m, or 3500 m (2±2) but increased (P<0.05) at 4000 m (3±1), 4300 m (6±4) and 4500 m (5±3). The % sleep did not decrease from SL (95±6) at 2000 m (95±21), 3000 m (87±21) and 3500 m (88±22) but decreased (P<0.05) at 4000 m (72±20), 4300 m (54±28) and 4500 m (63±25). These results suggest that although mean sleep SaO2 decreases at moderate altitudes, the threshold for significant sleep disturbances does not occur until 4000 m. Authors′ views; not official U.S. Army or DoD policy.