title: Comparison of Sleep Disorders between Real and Simulated 3,450-m Altitude.
abstract: Hypoxia is known to generate sleep-disordered breathing but there is a debate about the pathophysiological responses to two different types of hypoxic exposure: normobaric hypoxia (NH) and hypobaric hypoxia (HH), which have never been directly compared. Our aim was to compare sleep disorders induced by these two types of altitude.
  
  
  
  Subjects were exposed to 26 h of simulated (NH) or real altitude (HH) corresponding to 3,450 m and a control condition (NN) in a randomized order. The sleep assessments were performed with nocturnal polysomnography (PSG) and questionnaires. Thirteen healthy trained males subjects volunteered for this study (mean ± SD; age 34 ± 9 y, body weight 76.2 ± 6.8 kg, height 179.7 ± 4.2 cm).
  
  
  
  Mean nocturnal oxygen saturation was further decreased during HH than in NH (81.2 ± 3.1 versus 83.6 ± 1.9%; P < 0.01) when compared to NN (95.5 ± 0.9%; P < 0.001). Heart rate was higher in HH than in NH (61 ± 10 versus 55 ± 6 bpm; P < 0.05) and NN (48 ± 5 bpm; P < 0.001). Total sleep time was longer in HH than in NH (351 ± 63 versus 317 ± 65 min, P < 0.05), and both were shorter compared to NN (388 ± 50 min, P < 0.05). Breathing frequency did not differ between conditions. Apnea-hypopnea index was higher in HH than in NH (20.5 [15.8-57.4] versus 11.4 [5.0-65.4]; P < 0.01) and NN (8.2 [3.9-8.8]; P < 0.001). Subjective sleep quality was similar between hypoxic conditions but lower than in NN.
  
  
  
  Our results suggest that HH has a greater effect on nocturnal breathing and sleep structure than NH. In HH, we observed more periodic breathing, which might arise from the lower saturation due to hypobaria, but needs to be confirmed.
authors.affiliation: Center for Investigation and Research in Sleep, CHUV, Lausanne, Switzerland.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Heinzer
authors.affiliation: ISSUL, Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Switzerland.|Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Switzerland.
authors.forename: Jonas J
authors.initials: JJ
authors.lastname: Saugy
authors.affiliation: Savoie Mont Blanc University, Exercise Physiology Laboratory, Chambery, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Rupp
authors.affiliation: Center for Investigation and Research in Sleep, CHUV, Lausanne, Switzerland.
authors.forename: Nadia
authors.initials: N
authors.lastname: Tobback
authors.affiliation: ISSUL, Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Switzerland.|Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Switzerland.
authors.forename: Raphael
authors.initials: R
authors.lastname: Faiss
authors.affiliation: ISSUL, Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Switzerland.|Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bourdillon
authors.affiliation: Center for Investigation and Research in Sleep, CHUV, Lausanne, Switzerland.
authors.forename: José Haba
authors.initials: JH
authors.lastname: Rubio
authors.affiliation: ISSUL, Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Switzerland.|Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Switzerland.
authors.forename: Grégoire P
authors.initials: GP
authors.lastname: Millet
mesh_terms: D000328:Adult; D000531:Altitude; D001274:Atmospheric Pressure; D004780:Environment, Controlled; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000378:metabolism; D017286:Polysomnography; D012119:Respiration; D012890:Sleep / Q000502:physiology*; D012893:Sleep Wake Disorders / Q000378:metabolism* / Q000503:physiopathology*
chemical_list: D010100:Oxygen
keywords: hypobaric hypoxia; normobaric hypoxia; sleep disorders