Dependency of hypoxic pulmonary vasoconstriction on temperature

Abstract

We studied the effect of temperature change on hypoxic pulmonary vasoconstriction. Selective hypoxia on the left lower lobe of the lung in open-chested dogs at 37 degrees C caused the electromagnetically measured blood flow to the lobe to decrease 51 +/- 5 (SE)% and its vascular resistance to increase 155 +/- 25%. Testing hypoxic response. The hypoxic response at 31.1 +/- 0.4 degrees C was only a 26 +/- 6% decrease in lobar blood flow compared to the hypoxic response at 40.0 +/- 0.5 degrees C which was a 60 +/- 5% decrease in lobar blood flow. Hypothermia itself was associated with a significant increase in pulmonary vascular resistance. We conclude that hypothermia inhibits and hyperthermia enhances hypoxic pulmonary vasoconstriction. The mechanism of inhibition may involve prehypoxic vasoconstriction.