Hemodynamic response to hypoxia in dogs with chronic pulmonary hypertension

¹ Department of Physiology, Medical College of Georgia, Augusta, Georgia

Control dogs showed a clear increase in pulmonary resistance, in cardiac output, and in pulmonary arterial pressure when artifically ventilated with 10% O₂ under sodium pentobarbital anesthesia. Dogs with pulmonary hypertension from Dirofilariasis showed the same increase in pulmonary arterial resistance but no statistically significant change in pulmonary arterial pressure or in cardiac output when ventilated in the same manner and under the same anesthesia. The anoxia produced a greater lowering of arterial saturation in the hypertensive dogs but this is not enough to explain the clear differences in the response of cardiac output and pulmonary arterial pressure to the anoxic stimulus. It is hypothesized that failure of blood flow and pressure to increase significantly in the hypertensive animals is due to the inability of the chronically overloaded heart to increase its performance in response to anoxia and the accompanying sympathetic stimulation.

Key Words: heartworm disease in dogs • effect of hypoxia on pulmonary circulation • Dirofilariasis • cardiac output • hypoxia in chronic pulmonary hypertension (canine) • hypoxia and pulmonary vascular resistance

Submitted on February 18, 1964