Effect of perfusate temperature on pulmonary vascular resistance and compliance by arterial and venous occlusion in the rat.

The effect of different temperatures of perfusing fluid was tested on the pulmonary circulation of the rat. With increasing temperature, a decrease in overall pulmonary vascular resistance was observed, which depended on the associated reductions of arterial, venous and capillary vascular resistances. The highest sensitivity to temperature changes was exhibited by the venous segment. The overall sensitivity of pulmonary vessels to temperature caused a reduction in hydraulic resistance of about 1% for each 1 degrees C temperature increment. Compliance of pulmonary vessels increased when perfusate temperature was increased from between 25 and 35 degrees C to 45 degrees C, probably due to a direct effect of temperature on the stiffness of the vessel walls.