Short Half-Life Hypnotics Preserve Physical Fitness and Altitude Tolerance During Military Mountainous Training

ABSTRACTObjective: We study the effect of short half-life hypnotics (zaleplon or zolpidem against placebo) on altitude tolerance in 12 nonacclimated male soldiers (age, 22.1 ± 0.8 years; height, 177.8 ± 1.7 cm; weight, 69.8 ± 1.7 kg). Methods: Soldiers were trained to practice mountaineering at high altitude (2,533–4,810 meters) during 3 periods (one per medication tested) of 4 days (D1–D4). In each period the nights were spent in a hut (3,613 m). Administration of hypnotics or placebo was then implemented at 9:45 p.m. Nocturnal arterial oxygen saturation (SaO2) and heart rate variability (HRV) were monitored. At 5:00 a.m. and 9:00 p.m. physical fitness was assessed using acute mountain sickness (AMS) score. At 5:00 p.m., a posteffort stand test was carried out to evaluate the orthoparasympathetic imbalance with fatigue. Results: Nocturnal SaO2 correlated negatively with morning AMS scores (R = −0.820, p < 0.02) and HRV analysis favored the sympathetic modulation. Posteffort stand tests revealed that symp...