Breathing patterns under enflurane, halothane and propofol sedation in humans.

Abstract

Goodman and collegues (4) reported a fall in tidal volume (VT), ventilation (VE) and the inspiratory time:total time ratio (TI:Ttot) during propofol anaesthesia compared with the awake state. On the other hand, Rosa and coworkers (8) were unable to show any significant changes in respiratory frequency (f), VE, VT, inspiratory and expiratory time (TI,TE) and TI:Ttot during conscious sedation with low doses of propofol when compared with the awake state. Their results indicate that propofol at repeated small boluses of 0.3 and 0.6 mg. kg-1 does not produce significant alterations in inspiratory drive, respiratory pattern, gas exchange, or minute volume. Similar findings to those of Goodman (4) were published by Reich et al. (6) for the ventilatory effects of halothane at doses of 1.2 minimum alveolar concentration (MAC) and 1.7 MAC. They concluded that halothane caused a dose-dependent decrease in inspiratory drive and an increase in breathing frequency. The aim of our study was to investigate the effect of sedative doses of enflurane, halothane and propofol on breathing pattern, while maintaining end-tidal PCO2 1–2 Torr above the subjects’ natural resting value.