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Robust Adaptive Control of Hypnosis During Anesthesia


P. Grieder, A. Gentilini, M. Morari, T. Schnider

Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Istanbul, Turkey

A closed-loop controller for hypnosis was designed and validated on humans at our laboratory. The controller aims at regulating the Bispectral Index (BIS) - a surrogate measure of hypnosis derived from the electroencephalogram of the patient - with the volatile anesthetic isoflurane administered with a closed-circuit breathing system. The control algorithm consists of a cascaded Internal Model Controller (IMC) where the master loop aims at regulating BIS. The slave loop tracks endtidal concentration references provided by the master controller. In this paper, a new tuning method is presented. First, a robust design procedure which guarantees stability of the slave controller despite parametric uncertainties is described. Then, we will demonstrate how the estimation of the drug's equilibration constant $k_{e0}$ greatly improves performance if the estimated value is used to update the models in the control scheme. In order to do so, an identification scheme for $k_{e0}$ is proposed, which requires estimation of the drug's time to peak effect $t_{peak}$. The identification algorithm requires few modeling assumptions and guarantees convergence. Simulation results are presented, which quantify both the performance of the identification scheme and the improvement of the closed-loop control performance.


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M. Morari

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% Autogenerated BibTeX entry
@InProceedings { GriEtal:2001:IFA_921,
    author={P. Grieder and A. Gentilini and M. Morari and T. Schnider},
    title={{Robust Adaptive Control of Hypnosis During Anesthesia}},
    booktitle={Annual International Conference of the IEEE Engineering in
	  Medicine and Biology Society},
    address={Istanbul, Turkey},
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