Adaptive Control of Multiple Drug Infusions

Although various control schemes have been successful in controlling mean arterial blood pressure by infusing a vasoactive drug, the simultaneous control of cardiac output and blood pressure by multiple drug infusion has to-date received little attention. To this effect, this paper describes the design of an automated multiple drug delivery system. The proposed computer-based controller combines supervisory functions and adaptive control algorithms in a hierarchical structure. Given a set of measured cardiovascular parameters, the supervisor determines the underlying disordered physiology and initiates the relevant control mode. Each mode is a set of allowable drug types, set-point commands and single or multiple feedback loops. The feedback control laws are adapted to each patient's drug response. The adaptive scheme used here is based on pole-placement self-tuning algorithms. This design method accomodates constraints on maximum drug infusion and physiological response rates and, can deal with unknown varying time delays. Adaptive control appears to be better suited for this application because of the wide range of drug sensitivities among patients, time variations in parameters, unknown drug interaction and physiological distrubances.