| Anaesthesia comprises muscle relaxation, analgesia and unconsciousness. The depth of anaesthesia(DOA), the key parameter to estimate anaesthesia quality, is control object in operation. The target-controlled infusion(TCI), a vein dose regimen method in clinical anaesthesia, which is based on pharmacokinetics and pharmacodynamics and able to be used to implement proper target(plasma) dose concentration by adjusting dose regimen.The technology of intravenous anaesthesia has been improved and developed a lot since the birth of TCI in 1980's, whose basic is the traditional compartmental model. The lack of the model is that the pharmacokinetic parameter is only the average estimation of colony which is great different from the real case of individual. Physiologically-based pharmacokinetic model(PBPK model) is able to reflect the real change of dose concentration in human body, and depict real parameter of individual precisely. This paper analyzes the structure and sensitivity of the PBPK model in detail, based on which the anaesthesia control strategy is studied in virtue of the classical and modern control theory. For the first time, an advanced closed-loop control algorithm to compute the dose regimen of TCI, upon which a platform of anaesthesia closed-loop control is established and the dose regimen is applied to clinical experiment.Based on the research for the control strategy and algorithm of the TCI in anaesthesia, the key work is enclosed in the following three aspects:1. The closed-loop control theory guidance to the clinical anaesthesia infusionA new method was proposed to compute the dose regimen of TCI using closed-loop control arithmetic based on the reported PBPK physiological model of Propofol in human. The auditory evoked potentials index(AEPI)was considered as the target variable and the dose regimen was computed and applied in clinical anaesthesia. Comparing with traditional method, clinical results show that the dose regimen using this method was more precise. As we all know, physiological characteristic of different individuals can be reflected by physiological model. That makes it important to study the dose regimen for individual based on complex physiological model.2. The research for anaesthesia TCI by using iterative learning control(ILC) algorithmOn the basis of individual difference of population, the P-type iterative learning control algorithm, a hybrid controller combining P-ILC algorithm with general PID controller was designed in this paper. To modify present information with the prior system control experience and output error, the control parameters were not relied on the physiological parameters of control object. Hence, the system has broad adaptness and good robustness. The contradiction can be solved on parameter adjusting and physiological parameter difference of anesthesia object in traditional control algorithm.The TCI control demanding of all anesthesia objects with one control algorithm and parameter was realized by this system. The simulation results indicated that the hybrid controller could raise the final control accuracy of system and reduce the maladjustment of traditional PID control.3. The development of anaesthesia TCI research system and successful application in clinical practiceAn anesthesia TCI research system that complies to the clinical criterion was proposed in this paper. This system was composed of hardware equipment, software interface which was developed independently and algorithm of dose regimen curve in anesthesia process. The hardware system comprises anesthesia monitor(including non-invasion blood pressure monitor, multi-functional air monitor and AEPI monitor), close-loop control computer and micro-injection pump. With the use of online programmable technology of system control software, the step series changeable variable parameter control of anesthesia process can be realized and the multi-mode requirement of anesthesia scheme in experiment can be fulfilled.This system had been successfully applied in clinical experiments. 20 samples had been tested using this system and the results showed that: the average time approaching to steady state was reached was about 200s, the AEPI response speed was fast, the steady value of AEPI can be maintained at the target value 20, which shows agreement real measured AEPI curve and the simulation, in other words the clinical effects is good.The above results have not been reported yet and are new.In this paper comprehensive simulation is studied in strategy and arithmetic of TCI. The new algorithm is been applied to clinical surgery and satisfactory effects been obtained. So this work is of significance in both anaesthesia auto control theory and clinical individual dose regimen.
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