Clinical system engineering of long-term automatic thermal control during brain hypothermia under changing conditions

Abstract

Automatic control systems of brain temperature for water surface-cooling were first-ever applied to the brain hypothermic treatment of patients. A patient in ICU was regarded as a unity controlled system with an input (temperature of water into blanket) and an output (tympanic membrane temperature). The proposed algorithm of optimal-adaptive and fuzzy control laws inclusive of our developed cooling and warming machine were well confirmed during the hypothermic course to keep brain temperature of patients within its allowable range. It was well controlled without much influence due to room temperature, metabolic and circulatory change caused by various medical treatments including the effect of nonlinear and time-varying characteristics of individual patients. The clinical control of brain temperature was almost continuously performed in around 10 days, under the brain temperature between 35°C and 37°C scheduled by physicians according to the state of patients. Their state had been monitored during the therapeutic course of pharmacological treatment with almost everyday examinations by CT imaging, referring various vital signs inclusive of the temperature of urinary bladder with continuous measurement of intracranial pressure by a catheter placement in cerebral sinus. The patients had good recovery to their rehabilitation after mild hypothermia by the proposed automatic control systems.