title: Sleeping in moderate hypoxia at home for prevention of acute mountain sickness (AMS): a placebo-controlled, randomized double-blind study.
abstract: OBJECTIVE
  Acclimatization at natural altitude effectively prevents acute mountain sickness (AMS). It is, however, unknown whether prevention of AMS is also possible by only sleeping in normobaric hypoxia.
  
  
  METHODS
  In a placebo-controlled, double-blind study 76 healthy unacclimatized male subjects, aged 18 to 50 years, slept for 14 consecutive nights at either a fractional inspired oxygen (Fio2) of 0.14 to 0.15 (average target altitude 3043 m; treatment group) or 0.209 (control group). Four days later, AMS scores and incidence of AMS were assessed during a 20-hour exposure in normobaric hypoxia at Fio2 = 0.12 (equivalent to 4500 m).
  
  
  RESULTS
  Because of technical problems with the nitrogen generators, target altitude was not achieved in the tents and only 21 of 37 subjects slept at an average altitude considered sufficient for acclimatization (>2200 m; average, 2600 m). Therefore, in a subgroup analysis these subjects were compared with the 21 subjects of the control group with the lowest sleeping altitude. This analysis showed a significantly lower AMS-C score (0.38; 95% CI, 0.21 to 0.54) vs 1.10; 95% CI, 0.57 to 1.62; P = .04) and lower Lake Louise Score (3.1; 95% CI, 2.2 to 4.1 vs 5.1; 95% CI, 3.6 to 6.6; P = .07) for the treatment subgroup. The incidence of AMS defined as an AMS-C score greater than 0.70 was also significantly lower (14% vs 52%; P < .01).
  
  
  CONCLUSIONS
  Sleeping 14 consecutive nights in normobaric hypoxia (equivalent to 2600 m) reduced symptoms and incidence of AMS 4 days later on exposure to 4500 m.
authors.affiliation: University Hospital, Medical Clinic, Internal Medicine VII, Sports Medicine, Heidelberg, Germany. Electronic address: christoph.dehnert@gmx.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Dehnert
authors.affiliation: University Hospital, Medical Clinic, Internal Medicine VII, Sports Medicine, Heidelberg, Germany.
authors.forename: Astrid
authors.initials: A
authors.lastname: Böhm
authors.affiliation: University Hospital, Medical Clinic, Internal Medicine VII, Sports Medicine, Heidelberg, Germany.
authors.forename: Igor
authors.initials: I
authors.lastname: Grigoriev
authors.affiliation: University Hospital, Medical Clinic, Internal Medicine VII, Sports Medicine, Heidelberg, Germany.
authors.forename: Elmar
authors.initials: E
authors.lastname: Menold
authors.affiliation: University Hospital, Medical Clinic, Internal Medicine VII, Sports Medicine, Heidelberg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Bärtsch
mesh_terms: D000064:Acclimatization; D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000532:Altitude Sickness / Q000517:prevention & control*; D000693:Anaerobiosis; D004311:Double-Blind Method; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D012890:Sleep; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: acclimatization; acute mountain sickness; hypoxia; prevention; ventilation