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

Ventilation and oxygen consumption were measured in awake, unrestrained and unintubated guinea pigs during chronic and acute exposure to cold or hypoxia. Specific VE and VO2 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 VE and VO2 than that of control animals. Acclimation to cold did not result in respiratory advantages over that of control animals acutely exposed to cold. In hypoxia-acclimated guinea pigs, specific VE was 30% higher than that of control animals due to an elevation in VT; however, VO2 was similar in both groups of animals. In contrast, acute hypoxia did not increase VE 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.