The design of a bond-graph-based controller for muscle relaxant anaesthesia

This paper introduces a bond graph model-based controller which is based on a conceptual model that has been abstracted from the behaviour of atracurium administration for muscle relaxation. The process of drug administration is related to the macro action (the infusion rate of a syringe pump) and micro reaction (e.g. phenomena of distribution, elimination, absorption, and occupied receptors within the patient's body). The controller, designed by the concept of behaviour-orientation, has been structured in terms of an analogous mechanical system and interpreted from the view point of energy. The system model represented by the concept of component-orientation is derived from the three-compartment model using a pseudo bond graph. Two features are achieved: (1) the bond-graph-based controller can be applied for any proper impulse to increase the rise time in the non-linear system, (2) Model components of pseudo bond graph of atracurium relate to the physiological character of drug effect. Due to the essential non-linear dynamics of drug response a knowledge base which includes eight classes of sensitivities has been developed to aid controller sensitivity, and to choose corresponding initial conditions for a specific patient after giving a bolus dose. Simulation results from closed-loop studies of atracurium show very good performance using this innovative technique.