Effect of changes in airway pressure on breathing pattern in conscious dogs

The effect of brief (400 ms) or sustained (several breaths) application of positive or negative intrapulmonary air pressure was studied in three exercising conscious dogs. Changes in inspiratory duration (TI), expiratory duration (TE) and tidal volume (VT) were measured with the dogs' vagus nerves at body temperature and cooled to a temperature which abolished the Hering-Breuer inflation reflex (7 degrees C). Comparison of these results with those obtained with anaesthetized dogs leads us to suggest that there exists in conscious dogs a reflex inspiratory promoting drive.