Venous Chamber Pressure Control and Air Bubbles Detection in Hemodialysis Delivery System Based on Fuzzy Logic

Abstract

Air bubbles can enter the exctracorporeal hemodialysis circuit because of air trapped inside the tubing or because of a faulty pump connection. If a considerably dangerous amount of air bubble were to enter the veins, the patient will most likely to experience venous air embolism (VAE). To avoid the possibility of VAE, an air bubble detection along with an automatic clamping system is needed right before the blood is returned to the patients vein. A sudden change of venous chamber pressure during hemodalysis may cause hemolysis. This change of pressure can be caused by a kink in the venous chamber tubing, clotting in the patient's venous access, or a change in blood pump speed. A pressure sensor is required to monitor the pressure inside the hemodialysis venous chamber before the blood enters the vein. This study propose a device to monitor venous chamber pressure and detect air bubbles in the hemodialysis delivery system based on fuzzy logic. The pressure error and derivative error to the ideal pressure measured by the sensor will be the input of a DC motor speed control system to drive the peristaltic pump based on fuzzy logic controller (FLC). Output value of the designed FLC is Pulse Width Modulation (PWM) signal using a pressure sensor as the feedback. Air bubble detection is done by utilizing an air bubble sensor. Based on the DC motor test, saturation of rotation speed (RPM) occurs when given duty cycle of 84,3% and above. This was used as a consideration during the development of the fuzzy logic parameters, which results in the duty cycle given is between 65%-70%. The system needs 72,42 seconds to return to the set point when given disruption in the form of sudden increased pressure. It also needs 28,755 seconds to return to the set point when given disruption in the form of sudden pressure loss. Air bubble detection using the air bubble sensor has a result of 100% detection rate