John E. Peacock

Modelling and multivariable control in anaesthesia using neural-fuzzy paradigms Part II. Closed-loop control of simultaneous administration of propofol and remifentanil

OBJECTIVE Part II of this research study is concerned with the development of a closed-loop simulation linking the patient model as well as the fuzzy relational classifier already introduced in Part I with a control algorithm. The overall architecture is in fact a system advisor, which provides information to the anaesthetist about the adequate infusion-rates of propofol and remifentanil simultaneously. METHODS AND MATERIAL The developed fuzzy multivariable controller includes three rule-bases and takes into account the synergetic interactions between the above drugs and uses such knowledge to achieve rapidly the desired depth of anaesthesia (DOA) level. RESULTS The result of the study is a closed-loop control scheme, which adjusts efficiently the infusion-rates of two drugs in response to DOA changes. This controller can either be used in an advisory mode or closed-loop feedback mode in the operating theatre during surgery. CONCLUSION It is hoped that this control scheme coupled with the patient model presented in Part I of this study will be used routinely in the operating theatre in the very near future.

Fuzzy logic for auditory evoked response monitoring and control of depth of anaesthesia

This paper describes a self-organizing fuzzy model of patients undergoing surgery which was created from 10 clinical trials with off-line analysis during maintenance of anaesthesia using the drug propofol. The effects of patient sensitivity and surgical disturbances are also represented in this patient model. Hence, this model can be considered to be a qualitative pharmacologically related model for propofol during the anaesthetic maintenance stage. Furthermore, a closed-loop simulation has been designed to validate the patient model and compare the performance of a self-organizing fuzzy logic controller algorithm against a clinically derived linguistic controller. The successful results obtained provide proof-of-concept and encouragement to perform on-line clinical trials using fuzzy logic-based monitoring and control in operating theatre in the near future.

Propofol Induced Anaesthesia: A Comparative Control Study using a Derived Pharmacokinetic-Pharmacodynamic Model

Abstract The performance of protocols currently used for controlling the infusion of propofol intravenously and which assume a model based on an average pharmacokinetics population to predict the plasma concentration are shown to degrade when mismatch conditions between the patient and the model are considered. The pharmacokinetic model hence considered was extended to include pharmacodynamics by considering Mean Arterial Pressure measurements (thought to give a good indication of the anaesthetic state). Using this new extended model, the performances of two control strategies, modified Alvis algorithm and fixed Generalised Predictive Control (GPC) algorithm were assessed. The study reveals that under mismatch conditions the fixed GPC controller displays better properties than the modified Alvis algorithm making it a more attractive candidate for future clinical trials in theatre.