Effects of subanaesthetic sevoflurane on ventilation. 2: Response to acuteand sustained hypoxia in humans

We have determined the influence of 0.1 minimum alveolar concentration (MAC ) of sevoflurane on the acute ventilatory response to hypoxia (AHVR), hypox ic ventilatory decline (HVD) and the magnitude of the rapid decline in vent ilation on relief of sustained hypoxia (the off-response) in eight healthy adult volunteers. The following design was used with and without 0.1 MAC of sevoflurane: end-tidal PO2 was maintained at 13.3 kPa for 5 min, at 7.9 kP a for 20 min and at 13.3 kPa for 5 min. End-tidal PCO2 was held constant th roughout at 1.3 kPa above the subject's normal value. A dynamic end-tidal f orcing system was used to generate these gas changes. Sevoflurane reduced A HVR from 14.5 (SEM 1.2) to 11.6 (1.6) litre min(-1) and the off-response at cessation of hypoxia from 7.1 (1.1) to 6.3 (1.4) litre min(-1). The magnit ude of HVD was slightly increased by sevoflurane from 8.2 (1.1) to 10.6 (2. 8) litre min(-1) None of these changes was significant (ANOVA). These resul ts suggest that 0.1 MAC of sevoflurane had very little effect on the AHVR, and that it did not markedly alter the processes underlying HVD during sust ained hypoxia.