Importance

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Abstract

A method and system for rapid control of set inspired gas concentration is disclosed for operating a medical anesthesia delivery system and for controlling the flow and concentration of gases and anesthesia vapor delivered to a patient. Control of the inspired gas and agent concentration is accomplished by operating in different control priority modes. In a flow priority control mode, the user may set, either directly or indirectly, the total fresh gas flow rate. The total fresh gas flow rate can then be slowly be varied by the control algorithm, while the vaporizer concentration is actively controlled to achieve the user set inspired gas concentration. The invention includes a process for switching from the flow priority control mode into a concentration priority mode for low flow rates. By throttling the flow, the patient will receive nearly an instantaneous change in the amount of agent and fresh gas without having the transport delay associated with a change in the agent concentration. Sensors are used to monitor agent concentration and minute volume, and a processor is programmed to estimate the concentration of the agent in the pipeline to select the control priority mode, and control the agent vaporizer and the fresh gas flow controller to selectively switch between control priority modes and operate extremely efficiently while in the concentration priority mode by changing the flow rate instead of the agent concentration.

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First Claim