SEPARATE EFFECTS OF HALOTHANE AND CARBON DIOXIDE ON RESPIRATORY DURATION IN VAGOTOMIZED CATS

Abstract

The independent effects of halothane and CO2 on central mechanisms regulating respiratory frequency were investigated in 12 vagotomized, artificially ventilated cats. Changes in respiratory pattern analyzed from the phrenic neurogram revealed that increasing PaCO2 [arterial CO2 tension] at a constant depth of halothane anesthesia caused a progressive increase in TE [expiratory time] with various changes in TI [inspiratory time], whereas increasing the depth of halothane anesthesia at a constant PaCO2 caused a progressive decrease in TE with various changes in TI. Evidently the effect of CO2 on central mechanisms regulating respiratory duration is exactly the opposite of that produced by halothane and respiratory frequency is modified by both the depth of halothane anesthesia and PaCO2.