Effects of Body Temperature Changes on Hypoxic Pulmonary Vasoconstriction in Isolated Lungs of Rabbits

Ham, Byung Moon; Cheong, Il Young

Abstract

BACKGROUND: We studied the effects of body temperature changes and repeated hypoxic stimulation on hypoxic pulmonary vasoconstriction (HPV).
METHODS
We isolated lungs from 15 rabbits and perfused them at a constant flow of 30 ml/kg/min with a 3% albumin-physiologic salt solution containing autologous blood. After a 30-minute stabilization, the temperature of the perfusate was changed from 38oC to 32oC gradually. The lungs were ventilated for 15 minutes with a hyperoxic gas mixture consisting of 95% oxygen and 5% carbon dioxide and then for 5 minutes with a hypoxic gas mixture consisting of 3% oxygen and 5% carbon dioxide with the balance being nitrogen. We repeated the hypoxic stimulation 3 times at the same temperature. The mean pulmonary artery pressure changes and ventilation-related parameters were measured at each hypoxic stimulation.
RESULTS
With the first hypoxic stimulation, the hypoxic pressure response at the end of the 5-minute hypoxic period decreased significantly at 32oC. With the second and the third hypoxic stimulations, the hypoxic pressure responses at the end of the 5-minute hypoxic period decreased significantly at both 34oC and 36oC. With repeated hypoxic stimulations, the hypoxic pressure responses potentiated significantly at all temperatures. The baseline mean pulmonary artery pressure increased significantly below 34oC.
CONCLUSION
The HPV decreased with the reduction in body temperature and was potentiated by repeated intermittent hypoxia; also, the pulmonary vascular resistance increased with the reduction in the body temperature.