Effects of chronic lung denervation on breathing pattern and respiratory gas exchanges during hypoxia, hypercapnia and exercise.

The influence of vagal fibres from the lung on ventilatory responses to hypercapnia, hypoxia and exercise was studied in two intact dogs (C) and two chronically lung denervated dogs (C.L.D.). In intact dogs, inspiration duration did not change as tidal volume increased in response to increased chemical drives. Chronic lung denervation did not affect the hypercapnia- or hypoxia-induced elevations in V, despite significant changes in breathing pattern. During exercise, oxygen consumption was similar for C and C.L.D. animals. V for a given oxygen uptake was the same in C and C.L.D. dogs, but VT was higher in C.L.D. animals at all levels of exercise. It is concluded that vagal fibres from the lung play a role in determining the breathing pattern, but are not required for a normal ventilatory response to hypercapnia, hypoxia and exercise. Interaction between vagal sensory input and specific structures sensitive to chemical or physical stimuli is discussed.