title: Continuous positive airway pressure reduces loop gain and resolves periodic central apneas in the lamb.
abstract: Continous positive airway pressure (CPAP) is used to treat infant respiratory distress syndrome and apnea of prematurity, but its mode of action is not fully understood. We hypothesised that CPAP increases lung volume and stabilises respiratory control by decreasing loop gain (LG). Experimentally induced periodic breathing (PB) in the lamb was terminated early by CPAP in a dose-dependent manner, with a control epoch of 45.4+/-5.1s at zero CPAP falling to 32.9+/-5.4, 13.2+/-4.2 and 9.8+/-3.1s at 2.5, 5 and 10 cmH(2)O, respectively (p<0.001); corresponding duty ratios (duration of the ventilatory phase of PB divided by its cycle duration) increased from 0.50+/-0.02 to 0.62+/-0.05, 0.76+/-0.06 and 0.68+/-0.08, respectively (p<0.001). Since epoch duration and duty ratio are surrogate measures of LG, we conclude that CPAP ameliorates the effects of recurrent central apneas, and perhaps mixed and obstructive apneas, by decreasing LG via increases in lung volume.
authors.affiliation: Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash University, Monash Medical Centre, Clayton 3168, Australia.
authors.forename: Bradley A
authors.initials: BA
authors.lastname: Edwards
authors.forename: Scott A
authors.initials: SA
authors.lastname: Sands
authors.forename: Clare
authors.initials: C
authors.lastname: Feeney
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Skuza
authors.forename: Vojta
authors.initials: V
authors.lastname: Brodecky
authors.forename: Malcolm H
authors.initials: MH
authors.lastname: Wilkinson
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Berger
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D004195:Disease Models, Animal; D017286:Polysomnography / Q000379:methods; D011237:Predictive Value of Tests; D012123:Pulmonary Ventilation / Q000502:physiology*; D015656:Respiratory Mechanics; D012756:Sheep; D020182:Sleep Apnea, Central / Q000503:physiopathology* / Q000628:therapy*; D013990:Tidal Volume / Q000502:physiology