Abstract
Pulses (100 ms) of inflation and deflation were applied to the lungs of anesthetized rabbits before and during inactivation of pulmonary stretch receptors. Pulses of either sign given in inspiration often produced augmented breaths, whether or not stretch receptors were inactivated. Inflation pulses were more effective than deflation pulses. After an augmented breath it was impossible to produce another for at least 1 mn (refractoriness). Pulses of deflation always shortened expiration. Pulses of inflation early in expiration shortened expiration. Later in expiration, they lengthened expiration when stretch receptors were active and shortened expiration when stretch receptors were blocked. No refractoriness was observed for the effects on expiratory time. Pulses in paralyzed animals caused a burst of phrenic activity of fixed duration, usually with brief latency. There was no refractoriness. Apparently, the duration of inspiration is governed by the activity of pulmonary stretch receptors, except during an augmented breath, and the duration of expiration is governed by a balance of stretch and irritant receptor activity.