The existence of inhibitory vagal reflexes arising from cardiac and pulmonary receptors has been recognized for over a century. The cardiopulmonary region contains numerous receptors whose unmyelinated afferent fibers course in the vagus nerves and appear to exert a tonic influence on medullary areas related to heart beat and vasomotor activity. Studies on experimental animals and humans indicate that cardiopulmonary reflexes play an important role in blood pressure and blood volume control. 2. Experimental approaches include a selective decrease or increase of cardiopulmonary receptor activity by reducing or increasing central venous pressure in man, and stimulation of chemosensitive cardiac vagal endings in animals. These studies indicate that the inhibitory cardiopulmonary reflex function is altered in experimental and clinical hypertension. The cardiopulmonary dysfunction in hypertensive disease appears to be related to cardiac structural alterations secondary to the hypertensive state.
