title: Lower body positive pressure increases upper airway collapsibility in healthy subjects.
abstract: We previously showed that rostral fluid displacement by lower body positive pressure (LBPP) narrows the upper airway (UA) and increases UA resistance, but effects on UA collapsibility remained unknown. To test if LBPP increases UA collapsibility, 13 healthy men were randomized into a control or LBPP arm then crossed over into the other arm with a 30-min washout in between. LBPP was applied by inflating anti-shock trousers wrapped around both legs to 40 mmHg. UA collapsibility was assessed by determining UA critical closing pressure (P crit) during application of different negative airway pressures. P crit and leg fluid volume were measured at baseline and after 5 min during both periods. LBPP caused a significant increase in P crit associated with a reduction in leg fluid volume. We conclude that rostral fluid displacement by LBPP increases UA collapsibility in healthy men, suggesting that fluid shift into the neck could increase UA collapsibility during sleep and thereby predispose patients with fluid overload states to obstructive sleep apnea.
authors.affiliation: The Sleep Research Laboratory of the Toronto Rehabilitation Institute, Toronto, Ontario, 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: T Douglas
authors.initials: TD
authors.lastname: Bradley
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000502:physiology*; D000704:Analysis of Variance; D001794:Blood Pressure; D006801:Humans; D007866:Leg / Q000098:blood supply; D008297:Male; D009333:Neck / Q000502:physiology; D017286:Polysomnography; D011175:Positive-Pressure Respiration / Q000379:methods; D011187:Posture / Q000502:physiology*; D011312:Pressure; D011897:Random Allocation; D012119:Respiration; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*