title: Prevalence of positional sleep apnea in patients undergoing polysomnography.
abstract: OBJECTIVE
  The primary aim of this study was to determine the prevalence of positional obstructive sleep apnea using a functional definition. Positional sleep apnea was defined as a total apnea-hypopnea index (AHI) > or = 5 with a > 50% reduction in the AHI between the supine and nonsupine postures, and an AHI that normalizes (AHI < 5) in the nonsupine posture. A secondary aim was to determine if positional sleep apnea can be diagnosed accurately during a split-night study.
  
  
  METHODS
  Retrospective chart review.
  
  
  METHODS
  Two sleep centers in Buffalo, NY, one a Veterans Affairs Western New York Healthcare System Sleep Center (VAWNY) and the other a freestanding ambulatory center (Associated Sleep Center [ASC]).
  
  
  METHODS
  Three hundred twenty-six patients from the VAWNY, including 57 patients who underwent a split-night study and 242 patients from the ASC who underwent polysomnography.
  
  
  METHODS
  None.
  
  
  METHODS
  Patient characteristics and sleep study results.
  
  
  RESULTS
  Positional sleep apnea was seen in 49 of 99 patients (49.5%) with mild sleep apnea (AHI, 5 to 15/h), 14 of 72 patients (19.4%) with moderate sleep apnea (AHI, 15 to 30/h), and 5 of 77 patients (6.5%) with severe sleep apnea (AHI > 30/h). Sufficient sleep (> 15 min) in both postures was not seen in 104 of 269 patients (38.7%) and 80 of 242 overnight studies (33.1%) at the VAWNY and ASC, respectively, and was not seen in 47 of 57 split-night studies (82.5%). The percentage of studies with insufficient sleep in both postures was significantly greater for split-night studies (p < 0.0001).
  
  
  CONCLUSIONS
  Positional sleep apnea is common particularly in patients with mild disease. Positional sleep apnea cannot usually be assessed during a split-night study.
authors.affiliation: Division of Pulmonary, Critical Care & Sleep Medicine, Section 111S, State University of New York at Buffalo, Veterans Administration Medical Center, Veterans Affairs Western New York Healthcare Sytem, Buffalo, NY 14215, USA. mador@acsu.buffalo.edu
authors.forename: M Jeffery
authors.initials: MJ
authors.lastname: Mador
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Kufel
authors.forename: Ulysses J
authors.initials: UJ
authors.lastname: Magalang
authors.forename: S K
authors.initials: SK
authors.lastname: Rajesh
authors.forename: Veena
authors.initials: V
authors.lastname: Watwe
authors.forename: Brydon J B
authors.initials: BJ
authors.lastname: Grant
mesh_terms: D000328:Adult; D000368:Aged; D004569:Electroencephalography; D004585:Electrooculography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009518:New York / Q000453:epidemiology; D017286:Polysomnography / Q000706:statistics & numerical data*; D011187:Posture; D015995:Prevalence; D012189:Retrospective Studies; D012891:Sleep Apnea Syndromes / Q000145:classification / Q000453:epidemiology*