title: Respiratory load compensation in awake and sleeping dogs.
abstract: We have investigated immediate and progressive ventilatory responses to external elastic loads in five dogs with cervical vagal loops. Three dogs were studied while awake (W) and during non-REM sleep (S); the other two during barbiturate anesthesia (A). Elastic loads were applied at the end expiration for 1-6 breaths by having the dogs breathe from a rigid container (partial load) or against an occluded airway (infinite load). "Effective" elastance (EE) was determined from the tidal volume (VT)-tracheal pressure relationships of the unloaded, partially loaded, and infinitely loaded breaths. Passive thoracic elastance during W and S averaged 16.7 cmH2O/1. EE averaged 55.8 cmH2O/1 during W, 54.7 during S, and 59.5 during A. Vagal blockade (VB) induced large changes in VT but no change in EE in W or S; during A, EE decreased 37.5%. With sustained loading (partial) there was a progressive increase in VT but a corresponding increase in chemical (primarily hypoxic) respiratory drive, so that EE remained constant during five loaded breaths. VB augmented the progressive increase in VT during W or S but virtually abolished the increase in A. Thus the responses to elastic loads in W and S are similar and independent of conscious reactions or vagal influence; responses during A differ considerably. "Progressive load compensation" is a reflection of increasing of increasing chemical drive and not of progressive changes in EE.
mesh_terms: D000818:Animals; D004285:Dogs; D006935:Hypercapnia; D000860:Hypoxia; D008170:Lung Compliance; D010424:Pentobarbital; D012119:Respiration; D012890:Sleep / Q000502:physiology*; D013990:Tidal Volume; D014630:Vagus Nerve / Q000502:physiology; D014851:Wakefulness / Q000502:physiology*
chemical_list: D010424:Pentobarbital