Study on automatic control of hypnosis using inhalational anesthetics

本研究开发了一种控制系统，可根据催眠双谱指数调节吸入性麻醉剂七氟醚的激发浓度，以实现患者的理想麻醉。到目前为止，在吸入性麻醉中，药物的剂量通常是根据呼出的浓度来决定的。但是，为了达到理想的麻醉效果，即使同时使用静脉和吸入麻醉药，也必须根据患者的催眠情况调整吸入浓度。为此，我们研究了(1)代表它们相互作用的麻醉药作用模型，(2)催眠控制方法和个体参数的识别方法，以及(3)用于调节吸入麻醉剂吸入浓度的执行器。所得结果如下：(1)一个新的药效学模型，可以代表异丙酚，静脉麻醉剂和七氟醚的相互作用。该模型只有8个参数，异丙酚药效学模型4个参数，七氟醚药效学模型4个参数。仿真结果表明，该模型能够很好地描述丙泊酚和七氟醚在适当参数设置下的作用和相互作用。(2)考虑药物作用延迟时间和七氟醚激发浓度上界和下界，构建了丙泊酚和七氟醚同时使用催眠维持在理想水平的模型预测控制方法。提出了一种基于麻醉诱导过程中测量数据的个体药效学参数和延迟时间的识别方法。识别后开始催眠控制。仿真结果表明，所开发的控制系统能够将催眠控制在适当的范围内。(3)研制了一种用于调节七氟醚吸入浓度的安装驱动器样机。当安装执行器时，医生可以按常规方式调整浓度。少

In this study, a control system is developed that adjusts inspired concentration of sevoflurane, an inhalational anesthetic, based on Bispectral Index, a well-known hypnosis index, to realize a desired anesthesia for patients. Up to now, during anesthesia by an inhalational anesthetic the amount of the drug is usually administered based on exhaled breath concentration. But to realize a desired anesthesia the inspired concentration has to be adjusted based on patient's hypnosis even when both intravenous and inhalational anesthetics are used. For this purpose we study (1) a model of the effects of anesthetics that represents their interaction, (2) a hypnosis control method and an identification method of individual parameters, and (3) an actuator for adjusting inspired concentration of the inhalational anesthetic. The obtained results are as follows.(1) A novel pharmacodynamic model that can represent the interaction of propofol, an intravenous anesthetic, and sevoflurane. The model has … More only eight parameters, four parameters of the propofol pharmacodynamic model and four parameters of the sevoflurane pharmacodynamic model. Simulation results confirm that the model describes the effect and the interaction of propofol and sevoflurane when the parameters are set appropriately.(2) A model predictive control method for maintaining hypnosis at a desired level using both propofol and sevoflurane is constructed considering delay times of drug effects and upper and lower bounds of inspired concentration of sevoflurane. An identification method of individual pharmacodynamic parameters and delay time based on measured data during anesthesia induction is also developed. The hypnosis control is started after the identification. Simulation results confirm that the developed control system can keep hypnosis within a proper range.(3) A prototype of a mounting actuator for adjusting inspired concentration of sevoflurane is developed. Medical doctors can adjust the concentration in the usual way when the actuator is mounted. Less