The effect of limb movements on the regulation of depth and rate of breathing.

In anesthetized dogs and rabbits passive or active limb movements (1) shifted to the left the relationship between tidal volume (Vt) and inspiratory time (Ti), (2) lowered the relationship between expiratory time (Te) and Ti and decreased its slope, and (3) increased the output to the inspiratory muscles (Vt/Ti). These effects increased with increasing the frequency of movements. Similar effects were obtained after vagotomy. When the stimulus was started during expiration. Te was shorted in spite of the previous unaffected Ti, Arterial PCO2 during exercise was similar (active movements) or below (passive movements) control value. Since other chemical and physical humoral factors do not seem involved, the whole increase of ventilation should be produced by neurogenic stimuli. The time course of Te, Ti and VT/Ti at the onset and at the offset of limb movements indicates an abrupt and a slow component in the neurogenic drive. A single contraction of the limb during expiration of inspiration affected the timing and the VT/Ti of 3-8 breaths.