title: [Sites of obstruction in obstructive sleep apnea patients and their influencing factors: an overnight study].
abstract: OBJECTIVE
  To understand how sleep stage and position influence the mechanisms for pharyngeal collapse in different levels of upper airway (UA), overnight state-related changes and postural variation in obstructive sites in obstructive sleep apnea hypopnea syndrome (OSAHS) patients were studied.
  
  
  METHODS
  Fifty four OSAHS patients underwent overnight upper airway pressure monitoring during polysomnography. The lower limits of the UA obstruction were determined and their relationship with sleep stage, position, age, body mass index and apnea hypopnea index (AHI) were investigated.
  
  
  RESULTS
  All 54 patients had oropharynx (14 837 of the 23 172 analyzed events) and tongue base obstruction (5605/23,172), 2532 events were located at the oropharynx with extension to tongue base. Twenty nine patients has hypopharynx obstruction (105/23 172). Of the total amount of apnea hypopnea, the portions of obstruction located at tongue base level increased (t = 8.790, P = 0.000) in rapid eye movement (REM) sleep while those located at oropharynx decreased (t = -6.846, P = 0.000). Indexes of the apnea hypopnea caused by tongue base obstruction raised (t = 6.189, P = 0.000). Although the overall AHI in supine position was higher than in lateral position (t = 4.000, P = 0.000), increases in indexes of both the apnea hypopnea caused by tongue base (supine, 17.1 +/- 13.8 vs. lateral, 13.9 +/- 14.6) and oropharynx obstruction (44.3 +/- 20.3 vs. 37.2 +/- 25.9) were without significance (P > 0.05). Distribution of obstructive site varied little with different position (P > 0.05).
  
  
  CONCLUSIONS
  Upper airway obstruction involves more than one specific site of the upper airway and the oropharynx is the most common collapse site. Obstructive sites are likely to extend to lower levels during REM sleep. Sleep position has little effect on the distribution of obstructive site.
authors.affiliation: Department of Otorhinolaryngology Head and Neck Surgery, Affiliated Beijing Tongren Hospital, Capital University of Medical Sciences, Beijing 100730, China.
authors.forename: Yan-ru
authors.initials: YR
authors.lastname: Li
authors.forename: De-min
authors.initials: DM
authors.lastname: Han
authors.forename: Jing-ying
authors.initials: JY
authors.lastname: Ye
authors.forename: Yu-huan
authors.initials: YH
authors.lastname: Zhang
authors.forename: Guo-ping
authors.initials: GP
authors.lastname: Yin
authors.forename: Xiao-yi
authors.initials: XY
authors.lastname: Wang
authors.forename: Xiu
authors.initials: X
authors.lastname: Ding
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010614:Pharynx / Q000473:pathology* / Q000503:physiopathology*; D017286:Polysomnography; D011187:Posture; D020181:Sleep Apnea, Obstructive / Q000473:pathology* / Q000503:physiopathology*; D012894:Sleep Stages; D055815:Young Adult