[Comparative characteristics of respiratory and circulatory changes in acutely hyperthermic cats].

During three-hour heating, cats revealed two phases of changes in respiratory and circulatory systems: the compensatory phase corresponding to a moderate hyperthermia (rectal temperature 39.4 +/- 0.17 degrees C) and the decompensatory one developing at rectal temperature over 39.9 +/- 0.15 degrees C. In the first phase the alveolar ventilation, oxygen consumption, excretion of CO2 and one-minute respiratory volume increase to the same extent as the one-minute blood volume, the increased metabolism and heat production occurring against the background of the blood acid-alkaline homeostasis. In the second phase an imbalance of functions of respiratory and circulatory systems occurs leading to a decrease in the one-minute blood volume, an increase in the alveolar ventilation-lung blood flow ratio, a sharp drop of the pulmonary gas exchange and a respiratory alkalosis.