Effect of mechanical factors on the relation between rate and depth of breathing in cats.

In anesthetized tracheotomized cats we compared the time sequence of ventilatory events with neurological events (electrical activity of the diaphragm) during the breathing cycle. We found that under control conditions a phase shift existed between the neurological and the spirometric duration of inspiration, amounting to about 150 ms. This phase shift was increased by increasing the time constant of the respiratory system (resistive loading) and decreased by decreasing it (elastic loading). These phase shifts resulted in a difference in the appreciation of the volume responsible for the termination of inspiration (Hering-Breuer inhibition) because the volume corresponding to the end of the neurological event was somewhat smaller than the final tidal volume reached.