Tonic vagal influences on inspiratory duration.
The tidal volume (VT), inspiratory (Ti) and expiratory (Te) durations were determined in anesthetized rabbits, cats and dogs under normal conditions, during continuous positive or negative pressure breathing. Elastic loads up to complete occlusion of the airways were applied in order to determine the VT-Ti and Te-Ti relationships. The larger the end-expiratory lung volume the steeper the VT-Ti relationship, the smaller the increase of Ti and the greater the increase of Te produced by the load. Hence, the larger the end-expiratory lung volume the steeper the Te-Ti relationship. In vagotomized animals airways occlusion did not affect Ti and Te. Ti of occluded breaths in vagotomized animals was longer than that of occluded breaths in intact animals, whereas Te was similar at the resting volume of the respiratory system (FRC), shorter above FRC and longer below FRC. These results show that both phasic and tonic vagal discharges determine Ti and Te.
D000818:Animals; D002415:Cats; D004285:Dogs; D008176:Lung Volume Measurements; D011817:Rabbits; D012119:Respiration; D013045:Species Specificity; D013990:Tidal Volume; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology*