title: Upper airway resistance syndrome: effect of nasal dilation, sleep stage, and sleep position.
abstract: BACKGROUND
  The upper airway resistance syndrome (UARS) is one of the mild variants of obstructive sleep disordered breathing. Nasal obstruction is proposed as one of the mechanisms that lowers intrapharyngeal pressure and hence increases airway collapsibility.
  
  
  OBJECTIVE
  We evaluated the effect of external nasal dilation and sleep position on sleep in UARS.
  
  
  METHODS
  A double blind, randomized, controlled study with a crossover design (using therapeutic and placebo dilators) was conducted in 18 consecutive patients with UARS. Each patient had two overnight sleep studies one to two weeks apart. Cardiorespiratory parameters (AHI, percentage of time that SaO2 was more than 2% below awake [desaturation time] and mean overnight heart rate), sleep architecture (sleep stages, sleep efficiency, and arousal index), and body position were determined.
  
  
  RESULTS
  Application of the external nasal dilator resulted in a significant increase in the nasal cross-sectional area (p < 0.001). Treatment reduced stage 1 sleep (as a percent of total sleep time) from 8.6 +/- 0.8% to 7.1 +/- 0.7 (SEM), p = 0.034). Desaturation time was significantly lower with treatment (12.2 +/- 2.2% on placebo versus 9.1 +/- 1.3 on treatment, p = 0.04). There were no additional significant effects on the cardiorespiratory parameters, sleep architecture, or MSLT when the entire night was examined. Controlling for interactions of sleep stage and position and treatment we found that treatment reduced desaturation time (p = 0.03) but not AHI or arousal index. AHI was significantly lower in the lateral position compared to the supine (p = 0.0001) and in NREM sleep compared to REM (p = 0.001). Desaturation time was significantly lower on the lateral compared to the supine position (p = 0.002) and in NREM sleep compared to REM (p = 0.006). Arousal index was highly dependent on sleep stage (p = 0.0001): the index was higher in stage 2 compared to slow wave sleep and REM. Sleep position and treatment had no significant effect on arousals.
  
  
  CONCLUSIONS
  External nasal dilation reduced stage 1 sleep, an indirect marker of disrupted sleep, and desaturation time. There were no additional effects on sleep architecture or sleep disordered breathing. Both sleep position and sleep stage had a significant effect on sleep disordered breathing in UARS.
authors.affiliation: Sleep Disorders Centre, St. Boniface General Hospital, Winnipeg, Manitoba.
authors.forename: A S
authors.initials: AS
authors.lastname: Bahammam
authors.forename: R
authors.initials: R
authors.lastname: Tate
authors.forename: J
authors.initials: J
authors.lastname: Manfreda
authors.forename: M H
authors.initials: MH
authors.lastname: Kryger
mesh_terms: D000403:Airway Resistance / Q000502:physiology*; D001143:Arousal / Q000502:physiology; D018592:Cross-Over Studies; D004106:Dilatation; D004311:Double-Blind Method; D006801:Humans; D015508:Nasal Obstruction / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D010100:Oxygen / Q000097:blood; D017286:Polysomnography; D011187:Posture / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D012891:Sleep Apnea Syndromes / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D012894:Sleep Stages / Q000502:physiology; D012913:Snoring / Q000503:physiopathology / Q000628:therapy; D013018:Sound Spectrography
chemical_list: D010100:Oxygen