Effect of temperature on the ventilatory response curve to carbon dioxide in anaesthetized cats.

Effects of body temperature on the ventilatory control system were studied in 17 anaesthetized cats. At different body temperatures (stabilized within 0.1 degrees C) CO2 response curves were measured in each cat. In with chloralose-urethan anaesthetized cats it was found that in the body temperature range of 34-40 degrees C, in which neither shivering nor panting occurred, no statistically significant trend with temperature was found in the slope (S) and the extrapolated intercept on the PaCO2-axis (B) of the linear CO2 response curve during hyperoxia as well as hypoxia. In two with pentobarbital anaesthetized cats similar results were obtained. The resting ventilation (at FICO2 = 0) did not change significantly, while the resting PaCO2 during hyperoxia showed a trend to increase with temperature just reaching the level of significance (P less than 0.05). Breathing frequency increased significantly with temperature (P less than 0.0005). When body temperature was elevated above 41 degrees C both the slope (S) and the intercept of the CO2 response curve (B) decreased. In three cats ventriculo-cisternal perfusion was performed and no apparent influence of body temperature was found on the relation between the PCSFCO2 and PETCO2 and on the VE-PCSFCO2 response curves. These findings show that body temperature has no important modifying effect on the ventilatory response to CO2 in anaesthetized cats in the temperature range of 34-40 degrees C.