On an Automatic Intravenous Anesthesia Control System

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 11650445
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Control engineering
• Research Institution: KYOTO UNIVERSITY
• Principal Investigator: ARAKI Mituhiko Kyoto University, Graduate School of Engineering, Professor, 工学研究科, 教授 (60026226)
• Co-Investigator(Kenkyū-buntansha): ONODERA Hisashi Kyoto University, Graduate School of Medicine, Associate Professor, 医学研究科, 助教授 (50240825) ; FURUTANI Eiko Kyoto University, Graduate School of Engineering, Lecturer, 工学研究科, 講師 (40219118)
• Project Period (FY): 1999 – 2000
• Keywords: Intravenous anesthesia / Anesthesia control / Propofol / Bispectral Index / Model predictive control

Research Abstract

Recently, an intravenous anesthetic drug, propofol, which has less side effects and better characteristics than the other anesthetic drugs is developed. In this research, we have studied an index of anesthetic depth and an intravenous anesthesia control method using propofol in order to develop an automatic intravenous anesthesia control system for keeping patients' anesthetic depth at an appropriate level with minimal infusion of drug. To be concrete, we have studied 1) an appropriate index of anesthetic deptlt, 2) mathematical model of the response of the anesthetic depth to propofol infusion, and 3) a control system of the anesthetic depth using model predictive control. The obtained results are as follows.
Bispectral index (BIS) is the best index of anesthetic depth among the index of cardiovascular dynamics, median power frequency (MF), spectral edge frequency (SEF 95) and BIS.
From the data of anesthetic drug infusion and BIS during surgical operations, we made a mathematical model which describes the relation among the anesthetic drug infusion, the drug concentration in blood, effect-site concentration and BIS.The model consists of four-order transfer function with dead time and nonlinear function. Furthermore, since the dead time and the nonlinear function which describes the relation between effect-site concentration and BIS have much individual difference, we have developed a method of identifying them from the data of anesthetic drug infusion and BIS during anesthesia introduction.
We have developed an intravenous anesthesia control system using model predictive control. To evaluate the accuracy and reliability of our system, we made simulations under similar disturbances as in the actual operations. The results indicated that our system has enough performance.