title: Effects of positive airway pressure on patients with obstructive sleep apnea during acute ascent to altitude.
abstract: BACKGROUND
  In acute ascent to altitude, untreated obstructive sleep apnea (OSA) is often replaced with central sleep apnea (CSA). In patients with obstructive sleep apnea who travel to altitude, it is unknown whether their home positive airway pressure (PAP) settings are sufficient to treat their obstructive sleep apnea, or altitude-associated central sleep apnea.
  
  
  METHODS
  Ten participants with positive airway pressure-treated obstructive sleep apnea, who reside at 1,320 m altitude, underwent polysomnography on their home positive airway pressure settings at 1,320 m and at a simulated altitude of 2,750 m in a hypobaric chamber. Six of the participants were subsequently studied without positive airway pressure at 2,750 m.
  
  
  RESULTS
  At 1,320 m, all participants' sleep apnea was controlled with positive airway pressure on home settings; at 2,750, no participants' sleep apnea was controlled. At higher altitude, the apnea-hypopnea index was higher (11 vs. 2 events/h; P < 0.01), mostly due to hypopneas (10.5 vs. 2 events/h; P < 0.01). Mean oxygen saturations were lower (88 vs. 93%; P < 0.01) and total sleep time was diminished (349 vs. 393 min; P = 0.03). Four of six participants without positive airway pressure at 2,750 m required supplemental oxygen to prevent sustained oxygen saturation (as determined by pulse oximetry) less than 80%. Positive airway pressure also was associated with reduced central sleep apnea (0 vs. 1; P = 0.03), improved sleep time (358 vs. 292 min; P = 0.06), and improved sleep efficiency (78 vs. 63%; P = 0.04).
  
  
  CONCLUSIONS
  Acute altitude exposure in patients with obstructive sleep apnea treated with positive airway pressure is associated with hypoxemia, decreased sleep time, and increased frequency of hypopneas compared with baseline altitude. Application of positive airway pressure at altitude is associated with decreased central sleep apnea and increased sleep efficiency.
authors.affiliation: 1 Division of Pulmonary and Critical Care Medicine, University of Utah School of Medicine, Salt Lake City and.
authors.forename: Katsufumi
authors.initials: K
authors.lastname: Nishida
authors.affiliation: 1 Division of Pulmonary and Critical Care Medicine, University of Utah School of Medicine, Salt Lake City and.|2 Division of Pulmonary and Critical Care Medicine.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lanspa
authors.affiliation: 1 Division of Pulmonary and Critical Care Medicine, University of Utah School of Medicine, Salt Lake City and.|3 Division of Sleep Medicine, and.
authors.forename: Tom V
authors.initials: TV
authors.lastname: Cloward
authors.affiliation: 1 Division of Pulmonary and Critical Care Medicine, University of Utah School of Medicine, Salt Lake City and.|4 Division of Hyperbaric Medicine, Intermountain Medical Center, Murray, Utah.
authors.forename: Lindell K
authors.initials: LK
authors.lastname: Weaver
authors.affiliation: 1 Division of Pulmonary and Critical Care Medicine, University of Utah School of Medicine, Salt Lake City and.|2 Division of Pulmonary and Critical Care Medicine.
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Brown
authors.affiliation: 4 Division of Hyperbaric Medicine, Intermountain Medical Center, Murray, Utah.
authors.forename: James E
authors.initials: JE
authors.lastname: Bell
authors.affiliation: 1 Division of Pulmonary and Critical Care Medicine, University of Utah School of Medicine, Salt Lake City and.|2 Division of Pulmonary and Critical Care Medicine.
authors.forename: Colin K
authors.initials: CK
authors.lastname: Grissom
mesh_terms: D000531:Altitude; D000532:Altitude Sickness / Q000628:therapy*; D045422:Continuous Positive Airway Pressure / Q000009:adverse effects*; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000150:complications*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000627:therapeutic use; D017286:Polysomnography / Q000379:methods; D011446:Prospective Studies; D020182:Sleep Apnea, Central / Q000628:therapy*; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000628:therapy*; D014195:Travel
chemical_list: D010100:Oxygen
keywords: altitude; mountain sickness; sleep apnea