Pulsatile Physiological Control of Blood Pump-Cardiovascular System Based on Feedforward Compensation

Abstract

Rotary Blood Pump (RBP) is a commonly used ventricular assist device. However, the constant speed operation of the blood pump leads to a reduction of blood flow pulsatility, which triggers a series of adverse reactions. In this paper, a pulsatile physiological control with feed-forward compensation (FFC) is designed to regulate the rotational speed in real time to accurately output pulsatile blood flow to address this problem. The coupled model of the Rotary Blood Pump and cardiovascular system (CVS) is established in the SIMULINK software as the research object. The designed pulsatile physiological control algorithm contains the feed-forward compensation-based pulsatile control and anti-reflux algorithm, switching the applicable algorithm based on the pump flow. When the flow rate is higher than the threshold, feed-forward compensation is introduced and combined with PI feedback control to improve the performance of pulsation tracking; when the flow rate is lower than the threshold, it is switched to the anti-reflux algorithm to gradually increase the pump speed. Simulation shows that the designed feed-forward compensation link reduces the tracking error of the pulsatile physiological control by 80%. In the case of a 50% sudden change of physiological parameters, it can track quickly and stably and avoid reflux. The pulsatile performance and ventricular unloading performance are better compared with no feed-forward compensation pulsation control as well as constant-speed control. An increase of 30 mmHg in aortic beat-to-beat differential pressure was achieved in the extracorporeal circulation experiments, which is important for the realization of pulsatile flow control of the Rotary Blood Pump.

Keywords: Rotary Blood Pump; cardiovascular system; feed-forward compensation; physiological; pulsatility.

Figure 1

Equivalent circuit modeling of vascular networks [12].

Figure 2

Hydraulic performance testing of the RBP.

Figure 3

CVS schematic and Equivalent Circuit. (a) Cardiovascular Schematic. (b) Equivalent circuit diagram.

Figure 4

Equivalent circuit of CVS-RBP coupling model when implanted in parallel.

Figure 5

SIMULINK modeling of the CVS-RBP coupled system.

Figure 6

The equivalent circuit of RBP-CVS simplified by the assumptions.

Figure 7

Schematic diagram of the system structure under the action of the FFC-based pulsatile controller.

Figure 8

Schematic diagram of the switching process of pulsatile physiological control algorithm.

Figure 9

Response and tracking error signal curves of the system without FFC. 1. Reference Signal Input; 2. Response of the system without FFC at Kp = 50; 3. Response of the system without FFC at Kp = 100; 4. Response of the system without FFC at Kp = 300; 5. Tracking Error of the system without FFC at Kp = 50; 6. Tracking Error of the system without FFC at Kp = 100; 7. Tracking Error of the system without FFC at Kp = 300. The blue dotted line indicates the value of Aop₀.

Figure 10

Tracking performance at Kp = 300. 1. Reference Signal Input; 2. Response of the system with FFC; 3. Response of the system without FFC; 4. Tracking Error of the system without FFC; 5. Tracking Error of the system with FFC. The blue dotted line indicates the value of Aop₀.

Figure 11

The variation of physiological parameters.

Figure 12

Systemic response of three control methods to a 50% variation in physiological parameters.

Figure 13

Comparison of hemodynamic pulsatility performance among three control strategies.

Figure 14

Comparison of ventricular unloading performance among three control strategies.

Figure 15

Schematic diagram of extracorporeal circulation device.

Figure 16

Aortic pressure signaling in in vitro experiments.