title: Effect of rostral fluid shift on pharyngeal resistance in men with and without obstructive sleep apnea.
abstract: BACKGROUND
  Obstructive sleep apnea (OSA) relates to overnight rostral fluid shift, possibly because fluid accumulation around the pharynx increases pharyngeal resistance (Rph). We hypothesised that Rph will increase more in men with than without OSA in response to rostral fluid redistribution.
  
  
  METHODS
  Seventeen men with, and 12 without OSA were randomized to lower body positive pressure (LBPP) for 15min or control, then crossed over. Leg fluid volume (LFV) and Rph were measured before and after each period.
  
  
  RESULTS
  LBPP displaced similar amounts of fluid from the legs in both groups. However, compared to the non-OSA group, Rph increased significantly more during LBPP in the OSA group (-0.38±2.87 vs. 2.52±2.94cmH2O/l/s, p=0.016). Change in Rph during LBPP correlated directly with baseline Rph in the OSA group, but inversely in the non-OSA group.
  
  
  CONCLUSIONS
  OSA patients have increased susceptibility to pharyngeal obstruction in response to rostral fluid redistribution, which could predispose to pharyngeal collapse during sleep.
authors.affiliation: Sleep Research Laboratory, Toronto Rehabilitation Institute, Canada; Sleep Research Laboratory, Mount Sinai Hospital, Canada.
authors.forename: Laura H
authors.initials: LH
authors.lastname: White
authors.affiliation: Sleep Research Laboratory, Toronto Rehabilitation Institute, Canada; Sleep Research Laboratory, Mount Sinai Hospital, Canada.
authors.forename: Shveta
authors.initials: S
authors.lastname: Motwani
authors.affiliation: Sleep Research Laboratory, Toronto Rehabilitation Institute, Canada; Sleep Research Laboratory, Mount Sinai Hospital, Canada.
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Kasai
authors.affiliation: Sleep Research Laboratory, Toronto Rehabilitation Institute, Canada; Sleep Research Laboratory, Mount Sinai Hospital, Canada.
authors.forename: Dai
authors.initials: D
authors.lastname: Yumino
authors.affiliation: Sleep Research Laboratory, Toronto Rehabilitation Institute, Canada; Sleep Research Laboratory, Mount Sinai Hospital, Canada.
authors.forename: Vinoban
authors.initials: V
authors.lastname: Amirthalingam
authors.affiliation: Sleep Research Laboratory, Toronto Rehabilitation Institute, Canada; Sleep Research Laboratory, Mount Sinai Hospital, Canada; Sleep Research Laboratory, Centre for Sleep Medicine and Circadian Biology of the University of Toronto, Canada; Sleep Research Laboratory, Department of Medicine of the University Health Network Toronto General Hospital, Canada. Electronic address: douglas.bradley@utoronto.ca.
authors.forename: T Douglas
authors.initials: TD
authors.lastname: Bradley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000403:Airway Resistance / Q000502:physiology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D018495:Fluid Shifts / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010614:Pharynx / Q000502:physiology*; D017286:Polysomnography; D011312:Pressure; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D018709:Statistics, Nonparametric; D014851:Wakefulness; D055815:Young Adult
keywords: Obstructive sleep apnea; Rostral fluid shift; Upper airway