Effects of cold and hypoxia on ventilation and oxygen consumption in awake guinea pigs

Abstract

Ventilation and oxygen consumption were measured in awake, unrestrained and unintubated guinea pigs during chronic and acute exposure to cold or hypoixa. Specific V̇e and V̇ O 2 in acute and chronic exposure to cold were more than twice that of animals in normal environmental temperatures. Increased ventilation was mainly due to a 70% greater Vt in cold. Cold-acclimated guinea pigs returned acutely to normal temperatures, maintained higher V̇e and V̇ O 2 than that of control animals. Acelimation to cold did not result in respiratory advantages over that of control animals acutely exposed to cold. In Hypoxia-acclimated guinea pigs, specific V̇e was 30% higher than that of control animals due to an elevation in Vt; however, V̇ O 2 was similar in both group of animals. In contrast, acute hypoxia did not increase V̇e in control animals. This lack of ventilatory response to acute hypoxia apparently causes the marked erythropoiesis and the severe increase in hematocrit observed throughout chronic exposure to hypoxia. The high blood viscosity resulting from the increased hematocrit contributes to the right ventricular hypertrophy and cardiac failure in guinea pigs chronically exposed to hypoxia.