Luca Merigo

Event-Based control of depth of hypnosis in anesthesia

BACKGROUND AND OBJECTIVE In this paper, we propose the use of an event-based control strategy for the closed-loop control of the depth of hypnosis in anesthesia by using propofol administration and the bispectral index as a controlled variable. METHODS A new event generator with high noise-filtering properties is employed in addition to a PIDPlus controller. The tuning of the parameters is performed off-line by using genetic algorithms by considering a given data set of patients. RESULTS The effectiveness and robustness of the method is verified in simulation by implementing a Monte Carlo method to address the intra-patient and inter-patient variability. A comparison with a standard PID control structure shows that the event-based control system achieves a reduction of the total variation of the manipulated variable of 93% in the induction phase and of 95% in the maintenance phase. CONCLUSIONS The use of event based automatic control in anesthesia yields a fast induction phase with bounded overshoot and an acceptable disturbance rejection. A comparison with a standard PID control structure shows that the technique effectively mimics the behavior of the anesthesiologist by providing a significant decrement of the total variation of the manipulated variable.

A model-based control scheme for depth of hypnosis in anesthesia

Abstract In this paper we propose a model-based scheme to control the depth of hypnosis in anesthesia that uses the BIS signal as controlled variable. In particular, the control scheme exploits the propofol pharmacokinetics/pharmacodynamics model of the patient so that the estimated effect-site concentration is used as a feedback signal for a standard PID controller, which compensates for the model uncertainties. The tuning of the parameters is performed off-line using genetic algorithms to minimize a performance index over a given data set of patients. The effectiveness of the proposed method is verified by means of a Monte Carlo method that takes into account both the intra-patient and inter-patient variability. In general, we obtain a fast induction phase with limited overshoot and a good disturbance rejection during maintenance of anesthesia.

Event-based GPC for depth of hypnosis in anesthesia for efficient use of propofol

This work presents a simulation study of an event-based predictive control system for depth of hypnosis in anesthesia using bispectral index as a controlled variable. The developed control structure uses a Wiener model structure to exploit the linear model predictive approach. Due to this architecture it is possible to use a well-established model predictive controller for linear system taking advantage of constraints handling mechanism and keeping the computational effort in reasonable limits. In such a scheme, the predictive controller is implemented within adjustable virtual deadband on actuator to limit changes in control signal and preserve the control system resources. The presence of the virtual deadband permits to establish the tradeoff between control performance and the use of the control resources (propofol administration). This feature could reduce the risk of drug overdosis during the anesthesia reducing negative effects on patients health with postoperative delirium. The analyzed control system is evaluated for different values of the actuator deadband in order to test its influence on the controlled variable. Additionally, a comparison with a standard time-based predictive controller is performed.

Event based control of propofol and remifentanil coadministration during clinical anesthesia

In this paper we present an event-based methodology for the control of the depth of hypnosis in general anesthesia. The control system is based on the implementation of an event generator with strong noise filtering capabilities together with a PIDPlus controller and considers both the administration of propofol and remifentanil in order to obtained a desired level of the bispectral index scale. Simulation results obtained with a wide set of patients model demonstrate the effectiveness of the method in both the induction and maintenance phases and how the technique can be appreciated in practical cases as it mimics the behaviour of the anesthesiologist.

A noise-filtering event generator for PIDPlus controllers

Abstract In this paper we propose a new event generator, which has strong noise-filtering capabilities, to be used in event-based control systems with a PIDPlus controller. An approximate frequency analysis is performed in order to characterize the event generator system and tuning guidelines are provided for its design parameter. Simulation and experimental results obtained with a laboratory setup demonstrate the effectiveness of the methodology in providing a satisfactory performance related to set-point and load disturbance step responses with a total variation that is significantly reduced with respect to the standard cases.

A new event generator for PIPlus control systems

In this paper we propose a new event detector for control systems with a PIplus controller. Its main feature is its capability of filtering the noise in a very effective way, by generating a quantized signal. Practical guidelines are given for the selection of the parameters. Simulation results show the efficacy of the technique and that it outperforms the use of standard use of a Butterworth low-pass filter.