Pattern of breathing during hypoxia or hypercapnia of the awake or anesthetized cat

The breathing patterns during hypoxia and hypercapnia are similar in anesthetized cats but are qualitatively different in awake cats. The differences seen in the awake animals can be explained by either the central depressive effect of hypoxia or by a specific effect of hypercapnia on supra-pontine structures. The Breuer-Hering reflex sensitivity, i.e. the VT-TI relationship, appears, in the awake cat, quite similar to that recently described in man. The inspiratory activity is shown to be controlled by mechanisms dependent on the nature of the respiratory stimulation. The recent model proposed for the control of inspiration during anesthesia must be modified to account for the results observed in awake animal.