Adaptive Closed-Loop Control of End-Tidal Concentrations of Volatile Agents
In inducing anesthesia with the volatile agents, the goal is to rapidly achieve the desired brain concentration without creating a dangerously high level in the arterial blood. One protocol uses high fresh-gas flows (5 l/min) and an initial inspired concentration of 3–4 MAC. When the end-tidal concentration reaches the desired level, the vaporizer setting is reduced to 120% of the desired level. After 5 min the vaporizer is set to the desired level and the fresh-gas flow reduced to 1 l/min. Automatic control of this process could be implemented in a very straightforward way. Automation would reduce the human variability and might avoid potential injury when a clinician is busy with other tasks and forgets to reduce the vaporizer setting at the appropriate time. This chapter will review the design of the automatic controller and present its clinical advantages.
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