CHANGES IN THE RESPIRATORY PATTERN INDUCED BY HALOTHANE IN THE CAT

Abstract

The effect of halothane on the respiratory pattern was investigated in lightly anesthetized cats. Following the administration of 20% halothane there was a transient increase in respiratory frequency due to a decrease in the duration of expiration, followed by a progressive decrease in respiratory frequency due to prolongation of inspiration; both events could be demonstrated before and after vagotomy. During the steady-state obtained following the administration of 0.5, 1.0 and 1.5% halothane and after vagotomy there was a decrease in the duration of expiration and a progressive increase in the duration of inspiration. Tidal phrenic output decreased progressively as the concentration of halothane was increased. Changes in respiratory pattern seen during halothane anesthesia might involve some excitatory central mechanisms other than the bulbopontine system.