A NEW APPROACH TO BLOOD-PRESSURE AND BLOOD-VOLUME MODULATION DURING HEMODIALYSIS - AN ADAPTIVE FUZZY CONTROL MODULE

The paper proposes a fuzzy logic based procedure able to control as fa r as possible the behaviour of the blood pressure of a patient during a dialysis session, allowing him to reach the foreseen dry weight. A P I discrete-time fuzzy control is used in order to compare the controll ed variables concerning the (blood pressure and blood volume) to the r eference values. Two different reference tables, concerning the pressu re and volume errors and rates are introduced, then the proposed contr ol actions are mixed in order to obtain the final value (net ultrafilt ration rate). A smooth function of volemia acts on the second control variable, Na concentration in the dialysate. The adaptive control syst em was simulated on an IBM-PC, rules and terms were expressed by lingu istic judgements like: IF ''situation'', THEN ''action''. A pre-proces sor converts the rules into the numerical values of the reference tabl es. The obtained simulation results are satisfactory, the introduction of the Na control allows reaching the target dry weight of the patien t with a stable blood pressure.