PURPOSE: The present study evaluated the effects of a pre-acclimatization program comprising 7 passive 1-hour exposures to 4,500 m normobaric hypoxia on the prevalence and severity of acute mountain sickness (AMS) during a subsequent exposure to real high altitude in persons susceptible to AMS. METHODS: The project was designed as a randomized controlled trial including 32 healthy female and male participants with known susceptibility to AMS symptoms. After baseline measurements participants were randomly assigned to the hypoxia or the control group to receive the pre-acclimatization program (7 passive 1-hour exposures within 7 days to normobaric hypoxia or sham hypoxia). After completing pre-acclimatization, participants were transported (bus, cog railway) to real high altitude (Mönchsjoch hut, Switzerland, 3,650 m) and stayed there for 45 hours (2 nights). Symptoms of AMS and physiological responses were determined repeatedly. RESULTS: AMS incidence and severity did not significantly differ between groups during the high-altitude exposure. In total, 59 % of the hypoxia and 67 % of the control group suffered from AMS at one or more time points during the high-altitude exposure. Hypoxic and hypercapnic ventilatory responses were not affected by the pre-acclimatization program. Resting ventilation at high altitude tended to be higher (P = 0.06) in the hypoxia group compared to the control group. No significant between-group differences were detected for heart rate variability, arterial oxygen saturation, hematological and ventilatory parameters during the high altitude exposure. CONCLUSION: Pre-acclimatization using 7 passive 1-hour exposures to normobaric hypoxia corresponding to 4,500 m did not prevent AMS development during a subsequent high-altitude exposure in AMS-susceptible persons.
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Physical Therapy, Sports Therapy and Rehabilitation