Effect of Carotid Body Hypoxia and/or Hypercapnia on Pulmonary Vascular Resistance

Abstract

Abstract

The effect of carotid body hypoxia and/or hypercapnia on pulmonary vascular resistance was investigated in anesthetized open-chested dogs. The carotid bodies were perfused bilaterally with hypoxic and/or hypercapnic blood in systemically normoxic and normocapnic dogs. This was accomplished by pumping arterial autologous blood through a ventilated extracorporeal lung to the common carotid arteries. Before vagotomy, carotid body hypoxia decreased cardiac output but did not alter any pulmonary vascular parameter measured or calculated. After vagotomy, carotid body hypoxia again decreased cardiac output while pulmonary vascular resistance increased. During hypoxia-hypercapnia mean pulmonary artery and pulmonary artery pulse pressures and pulmonary vascular resistance increased. Hypercapnia caused no change in any pulmonary vascular parameter measured or calculated. Following α-blockade with phentolamine pulmonary vascular resistance failed to increase during carotid body hypoxia or hypoxia-hypercapnia. We conclude that in the vagotomized dog carotid body hypoxia and hypoxia-hypercapnia reflexly increase pulmonary vascular resistance and that this effect is mediated by α-adrenergic receptors.