title: Effect of added dead space on sleep disordered breathing at high altitude.
abstract: OBJECTIVE
  Sleep disordered breathing with central apnea or hypopnea frequently occurs at high altitude and is thought to be caused by a decrease in blood CO(2) level. The aim of this study was to assess the effects of added respiratory dead space on sleep disordered breathing.
  
  
  METHODS
  Full polysomnographies were performed on 12 unacclimatized swiss mountaineers (11 males, 1 female, mean age 39 ± 12 y.o.) in Leh, Ladakh (3500 m). In random order, half of the night was spent with a 500 ml increase in dead space through a custom designed full face mask and the other half without it.
  
  
  RESULTS
  Baseline data revealed two clearly distinct groups: one with severe sleep disordered breathing (n=5, AHI>30) and the other with moderate to no disordered breathing (n=7, AHI<30). DS markedly improved breathing in the first group (baseline vs DS): apnea hypopnea index (AHI) 70.3 ± 25.8 vs 29.4 ± 6.9 (p=0.013), oxygen desaturation index (ODI): 72.9 ± 24.1/h vs 42.5 ± 14.4 (p=0.031), whereas it had no significant effect in the second group or in the total population. Respiratory events were almost exclusively central apnea or hypopnea. Microarousal index, sleep efficiency, and sleep architecture remained unchanged with DS. A minor increase in mean PtcCO(2) (n=3) was observed with DS.
  
  
  CONCLUSIONS
  A 500 ml increase in dead space through a fitted mask may improve nocturnal breathing in mountaineers with severe altitude-induced sleep disordered breathing.
authors.affiliation: Pulmonary Department and Centre for Investigation and Research in Sleep (CIRS), Lausanne University Hospital (CHUV), Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Lovis
authors.forename: M
authors.initials: M
authors.lastname: De Riedmatten
authors.forename: D
authors.initials: D
authors.lastname: Greiner
authors.forename: G
authors.initials: G
authors.lastname: Lecciso
authors.forename: D
authors.initials: D
authors.lastname: Andries
authors.forename: U
authors.initials: U
authors.lastname: Scherrer
authors.forename: A
authors.initials: A
authors.lastname: Wellman
authors.forename: C
authors.initials: C
authors.lastname: Sartori
authors.forename: R
authors.initials: R
authors.lastname: Heinzer
mesh_terms: D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000097:blood / Q000503:physiopathology / Q000628:therapy*; D002245:Carbon Dioxide / Q000097:blood; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008397:Masks; D008875:Middle Aged; D009051:Mountaineering / Q000502:physiology*; D017286:Polysomnography; D012126:Respiratory Dead Space / Q000502:physiology*; D012138:Respiratory Therapy / Q000379:methods*; D012891:Sleep Apnea Syndromes / Q000097:blood / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome
chemical_list: D002245:Carbon Dioxide