Automated control of end-tidal inhalation anaesthetic concentration using the GE Aisys Carestation™

Abstract

Automated control of end-tidal inhalation anaesthetic concentration is now possible. The EtControl™ module of an Aisys Carestation Anaesthetic machine digitally adjusts fresh gas flow and plenum vaporizer output to achieve a target end-tidal concentration. We evaluated EtControl in clinical practice by measuring volatile agent consumption and the need for user input. We compared these values with contemporaneous controls using manual control of fresh gas flow rates. A total of 321 patients were anaesthetized with EtControl and 168 with manual control of fresh gas flow. The mean [95% confidence interval (CI)] sevoflurane usage for cases of 20-40 min duration was 14 (13-16) ml h(-1) with EtControl and 30 (26-35) ml h(-1) with manual control. For cases of the same duration, the mean (95% CI) desflurane consumption was 27 (21-33) ml h(-1) with EtControl and 45 (29-62) ml h(-1) with manual control. The average number of keypresses per case was 6.5 with EtControl and 13.6 during manual control of fresh gas flow. Automatic implementation of low-flow anaesthesia using EtControl allows the user to set and maintain a desired end-tidal volatile concentration while using less volatile agent.