title: Difference in upper airway collapsibility during wakefulness between men and women in response to lower-body positive pressure.
abstract: Fluid shift from the legs to the neck induced by LBPP (lower-body positive pressure) increases UA (upper airway) collapsibility in healthy men. Rostral fluid displacement during recumbency may therefore contribute to the pathogenesis of OSA (obstructive sleep apnoea). There is a higher prevalence of OSA in men than in women. We therefore hypothesized that UA collapsibility increases more in men in response to rostral fluid displacement than in women. UA collapsibility was assessed in healthy, non-obese men and women while awake by determining UA Pcrit (critical closing pressure) during application of different suction pressures to the UA. Subjects were randomized to 5 min control or LBPP arms after which they crossed-over into the other arm following a 30 min washout. LBPP was applied by inflating anti-shock trousers wrapped around both legs to 40 mmHg. Pcrit, leg fluid volume and neck circumference were measured at baseline and after 5 min of both control and LBPP periods. LBPP caused a decrease in leg fluid volume and an increase in neck circumference that did not differ between men and women. However, compared with the control period, LBPP induced a much greater increase in Pcrit in men than in women (7.2+/-1.8 compared with 2.0+/-1.5 cm H2O, P=0.035). We conclude that rostral fluid displacement by LBPP increases UA collapsibility more in healthy, non-obese men than in women. This may be one mechanism contributing to the higher prevalence of OSA in men than in women.
authors.affiliation: Sleep Research Laboratory of the Toronto Rehabilitation Institute, Toronto, ON M5G 2A2, Canada.
authors.forename: Mao-Chang
authors.initials: MC
authors.lastname: Su
authors.forename: Kuo-Liang
authors.initials: KL
authors.lastname: Chiu
authors.forename: Pimon
authors.initials: P
authors.lastname: Ruttanaumpawan
authors.forename: Satomi
authors.initials: S
authors.lastname: Shiota
authors.forename: Dai
authors.initials: D
authors.lastname: Yumino
authors.forename: Stefania
authors.initials: S
authors.lastname: Redolfi
authors.forename: James S
authors.initials: JS
authors.lastname: Haight
authors.forename: Brian
authors.initials: B
authors.lastname: Yau
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lam
authors.forename: T Douglas
authors.initials: TD
authors.lastname: Bradley
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000502:physiology*; D000886:Anthropometry; D001794:Blood Pressure / Q000502:physiology; D018592:Cross-Over Studies; D005260:Female; D018495:Fluid Shifts / Q000502:physiology*; D005676:Gravity Suits; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008176:Lung Volume Measurements / Q000379:methods; D008297:Male; D009333:Neck / Q000033:anatomy & histology; D012727:Sex Characteristics; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology; D014851:Wakefulness / Q000502:physiology*