title: Postural effects on pharyngeal protective reflex mechanisms.
abstract: OBJECTIVE
  Pharyngeal muscle dilators are important in obstructive sleep apnea pathogenesis because the failure of protective reflexes involving these muscles yields pharyngeal collapse. Conflicting results exist in the literature regarding the responsiveness of these muscles during stable non-rapid eye movement sleep. However, variations in posture in previous studies may have influenced these findings. We hypothesized that tongue protruder muscles are maximally responsive to negative pressure pulses during supine sleep, when posterior tongue displacement yields pharyngeal occlusion.
  
  
  METHODS
  We studied all subjects in the supine and lateral postures during wakefulness and stable non-rapid eye movement sleep by measuring genioglossus and tensor palatini electromyograms during basal breathing and following negative pressure pulses.
  
  
  METHODS
  Upper-airway physiology laboratory of Sleep Medicine Division, Brigham and Women's Hospital.
  
  
  METHODS
  17 normal subjects.
  
  
  RESULTS
  We observed an increase in genioglossal responsiveness to negative pressure pulses in sleep as compared to wakefulness in supine subjects (3.9 percentage of maximum [%max] +/- 1.1 vs 4.4 %max +/- 1.0) but a decrease in the lateral decubitus position (4.1 %max +/- 1.0 vs 1.5 %max +/- 0.4), the interaction effect being significant. Despite this augmented reflex, collapsibility, as measured during negative pressure pulses, increased more while subjects were in the supine position as compared with the lateral decubitus position. While the interaction between wake-sleep state and position was also significant for the tensor palatini, the effect was weaker than for genioglossus, although, for tensor palatini, baseline activity was markedly reduced during non-rapid eye movement sleep as compared with wakefulness.
  
  
  CONCLUSIONS
  We conclude that body posture does have an important impact on genioglossal responsiveness to negative pressure pulses during non-rapid eye movement sleep. We speculate that this mechanism works to prevent pharyngeal occlusion when the upper airway is most vulnerable to collapse eg, during supine sleep.
authors.affiliation: Sleep Medicine and Pulmonary/Critical Care Divisions, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. amalhotra1@partners.org
authors.forename: Atul
authors.initials: A
authors.lastname: Malhotra
authors.forename: John
authors.initials: J
authors.lastname: Trinder
authors.forename: Robert
authors.initials: R
authors.lastname: Fogel
authors.forename: Michael
authors.initials: M
authors.lastname: Stanchina
authors.forename: Sanjay R
authors.initials: SR
authors.lastname: Patel
authors.forename: Karen
authors.initials: K
authors.lastname: Schory
authors.forename: Darci
authors.initials: D
authors.lastname: Kleverlaan
authors.forename: David P
authors.initials: DP
authors.lastname: White
mesh_terms: D000328:Adult; D015992:Body Mass Index; D005260:Female; D005683:Gagging / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010609:Pharyngeal Muscles / Q000502:physiology; D011187:Posture / Q000502:physiology*; D011312:Pressure; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000517:prevention & control*; D012894:Sleep Stages / Q000502:physiology; D014059:Tongue / Q000502:physiology; D014851:Wakefulness / Q000502:physiology