Automatic control of blood pressure by drug infusion

Abstract

Automatic control of arterial blood pressure by infusing the drug sodium nitroprusside is used for the treatment of elevated blood pressure after open-heart surgery at the Cardiac Surgical Intensive Care Unit of the University of Alabama Hospital. Controller design was based on investigations of the dynamics of the physiological responses of patients to nitroprusside infusion. A nonlinear PID digital controller has been used on over 1700 patients. Clinical experiences have shown that automatic control is safe and effective. The wide range of patient characteristics we have observed warranted the design of an improved controller.For analysis, design and evaluation, a model of the system related to arterial pressure and its response to nitro prusside was developed, and patient care practices were analysed. An adaptive multiple-mode multirate sampled-data controller was designed using model-based techniques, and was implemented with a microcomputer system. Simulation results were verified by experiments in the animal laboratory. Results from clinical evaluations with postsurgical patients were superior to the performance of previous automated infusion systems.