Drug Infusion System

Critical care patients have often suffered a "disturbance" to the normal operation of their physiological system; this disturbance could have been generated by surgery or some sort of trauma (e.g. a heart attack). A responsibility of the critical care physician is to maintain certain patient outputs within an acceptable operating range. Two important outputs to be maintained are mean arterial pressure (MAP) and cardiac output (CO). Often the anesthesiologist will infuse several drugs into the patient in order to control these states close to the desired values. A conceptual diagram is shown in Figure 1.

Figure 1. Drug Infusion Control

The goal of this control system design is to manipulate the flowrate of two drugs, sodium nitroprusside (SNP) and dopamine (DPM) to maintain the two outputs (MAP and CO) at their desired setpoints. A successful implementation of such a strategy allows the anesthesiologist to spend more time monitoring other patient states, such as "depth of anesthesia".

A significant number of research articles have been published in the IEEE Transcations on Biomedical Engineering. Isaka and Sebald (1993), review various modelling and control strategies for SISO control of MAP. Voss et al. (1987) and Yu et al.(1992) discuss advanced control strategies for this multivariable control problem.

In this case study, you will be required to

• model and identify the responses of a patient, interms of transfer functions, to the two drug inputs
• develop a multivariable controller to monitor the patient and
• test its performance and disturbance rejection capabilities.

References :

Isaka S., and A.V. Sebald, Control strategies for arterial blood pressure regulation. IEEE Transactions on Biomedical Engineering v. 40, p. 353-63, 1993.

Voss G. I., P.G. Katona, and H.J. Chizeck, Adaptive multivariable drug delivery : Control of arterial pressure and cardiac output in anesthetized dogs. IEEE Transactions on Biomedical Engineering v. 34, p. 617-23, 1987.

Yu C., R. J. Roy, H. Kaufman, and B. W. Bequette, Multiple model adaptive predictive control of arterial pressure and cardiac output. IEEE Transactions on Biomedical Engineering v. 39, p. 765-78, 1992.