A Sensorless Suction-Index based Feedback Control Strategy for Rotary Right Ventricular Assist Devices

Objective: The rotary right ventricular assist devices (RVAD) are mechanical pumps used to provide long-term circulatory support for the patients with right heart failure, which often occurs after occurrence of left heart failure or on its own. In this study, we proposed a new sensorless and suction index (SI) based control algorithm in order to provide sufficient cardiac output and achieve suction avoidance under varying physical activities. Methods: The proposed SI control strategy used a gain-scheduled proportional-integral (PI) controller to maintain the actual calculated values of SI close to a user-defined reference value. SI was extracted based on the RVAD flow rates, which were estimated from the intrinsic pump parameter (noisy pump speed measurements) using Golay-Savitzky (GS) filters. A nonlinear model of the human circulatory system was coupled with the RVAD to evaluate performance of the SI control strategy in-silico. The proposed SI control algorithm was compared to the constant pump speed (RPM) control strategy during (1) rest and exercise conditions, and (2) a rapid 2-fold increase in vena caval resistance (VCR) for (1). Results and Conclusion: The SI control strategy effectively avoided suction events while providing sufficient cardiac output during varying physiologic conditions and was better than the constant RPM control strategy. Significance: The proposed SI control method can eliminate the unreliable and non-long-term used sensors, and can be easily applied to current pumps for suction prevention and physiological perfusion.