title: Seven Passive 1-h Hypoxia Exposures Do Not Prevent AMS in Susceptible Individuals.
abstract: The present study evaluated the effects of a preacclimatization program comprising seven passive 1-h exposures to 4500-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.
  
  
  
  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 preacclimatization program (seven passive 1-h exposures within 7 d to normobaric hypoxia or sham hypoxia). After completing preacclimatization, participants were transported (bus, cog railway) to real high altitude (3650 m, Mönchsjoch Hut, Switzerland) and stayed there for 45 h (two nights). Symptoms of AMS and physiological responses were determined repeatedly.
  
  
  
  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 preacclimatization program. Resting ventilation at high altitude tended to be higher (P = 0.06) in the hypoxia group compared with the control group. No significant between-group differences were detected for heart rate variability, arterial oxygen saturation, and hematological and ventilatory parameters during the high-altitude exposure.
  
  
  
  Preacclimatization using seven passive 1-h exposures to normobaric hypoxia corresponding to 4500 m did not prevent AMS development during a subsequent high-altitude exposure in AMS-susceptible persons.
authors.affiliation: 1Department of Sport Science, University of Innsbruck, Innsbruck, AUSTRIA; 2Austrian Society of Alpine and High Altitude Medicine, Innsbruck, AUSTRIA; 3Department for Medical Sciences and Health System Management, Institute for Sports Medicine, Alpine Medicine and Health Tourism, Hall in Tirol, Tyrol, AUSTRIA; 4Department of Internal Medicine, University of Pavia, Pavia, ITALY; and 5Folkhälsan Institute of Genetics, Folkhälsan Research Center, University of Helsinki, Helsinki, FINLAND.
authors.forename: Martin
authors.initials: M
authors.lastname: Faulhaber
authors.forename: Elena
authors.initials: E
authors.lastname: Pocecco
authors.forename: Hannes
authors.initials: H
authors.lastname: Gatterer
authors.forename: Martin
authors.initials: M
authors.lastname: Niedermeier
authors.forename: Maike
authors.initials: M
authors.lastname: Huth
authors.forename: Tobias
authors.initials: T
authors.lastname: Dünnwald
authors.forename: Verena
authors.initials: V
authors.lastname: Menz
authors.forename: Luciano
authors.initials: L
authors.lastname: Bernardi
authors.forename: Martin
authors.initials: M
authors.lastname: Burtscher
mesh_terms: D000064:Acclimatization; D000328:Adult; D000532:Altitude Sickness / Q000453:epidemiology / Q000503:physiopathology / Q000517:prevention & control*; D001784:Blood Gas Analysis; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010100:Oxygen / Q000097:blood; D015995:Prevalence; D012119:Respiration; D012720:Severity of Illness Index; D013557:Switzerland
chemical_list: D019344:Lactic Acid; D010100:Oxygen