Control Strategy for Maintaining Physiological Perfusion with Rotary Blood Pumps

Abstract

We present arguments and simulation results in favor of a novel strategy for control of rotary blood pumps. We suggest that physiological perfusion is achieved when the blood pump is controlled to maintain an average reference differential pressure. In the case of rotary left ventricular assist devices, our simulations show that maintaining a constant average pressure difference between the left ventricle and aorta results in physiological perfusion over a wide range of physical activities and clinical cardiac conditions. We simulated rest, light, and strenuous exercise conditions, corresponding to cardiac demands of 4.92, 7.98, and 14.62 L/min, respectively. For different exercise levels, the clinical conditions ranged from normal to failing to asystolic heart. By maintaining a constant pressure difference of 75 mm Hg between the left ventricle and aorta, with either an axial or a centrifugal blood pump, a total cardiac output close to the physiological cardiac demand was achieved, irrespective of the heart condition. The simulations of the transitions between different levels of exercise indicate that with the same reference differential pressure, the proposed approach leads to rapid adaptation of the total cardiac output to physiological levels, while avoiding suction. Comparison with the traditional control strategy of maintaining a reference rotational speed (rpm) of the pump indicates that though the traditional approach has some degree of adaptability, it is only adequate over a narrow range of cardiac demand and clinical conditions of the patient. Our results indicate that the proposed approach is superior to the alternatives in providing an adequate and autonomous adaptation of the total cardiac output over a broad range of exercise conditions (expected when an assist device is used as a destination therapy) and clinical statuses of the native heart (such as further deterioration or recovery of cardiac function), while having the potential to improve the quality of life of patients by reducing the need for monitoring and frequent human intervention. The proposed approach can be clinically implemented using simple controllers, and requires the implantation of two pressure sensors, or estimation of the pressure difference based on other available measurements.

Automatic control of dual left ventricular assist devices as a biventricular assist device

“…The two differential pressure controllers presented by Giridharan and colleagues, ΔP and ΔPaolv, exhibited higher pump flows in exercise than constant speed control, with ΔPaolv producing higher flows than ΔP. These results align with those initially presented by Giridharan in [112], [152]. Additional findings from this study were that the differential pressure control strategies did not reduce pump speed sufficiently in response to a change in preload to prevent ventricular suction.…”

“…However, [74] the control objectives that are described in the next chapter are almost all pump-independent. Giridharan and Skliar established this by testing their control system using both axial and centrifugal pumps [106].…”

“…The most significant investigations into ΔP control were performed by Giridharan and colleagues [106], [112], [123], [153]- [155]. These authors extended on the previous work by evaluating ΔP control of both axial and centrifugal pumps.…”

Predicted Hemodynamic Benefits of Counterpulsation Therapy Using a Superficial Surgical Approach

“…[9][10][11][12][13] Briefly, the human circulatory model subdivides the human circulatory system into an arbitrary number of lumped parameter blocks, each characterized by its own resistance, compliance, pressure, and volume of blood. Two idealized elements, resistance and storage, were used to characterize each block.…”

Computational modelling and evaluation of cardiovascular response under pulsatile impeller pump support

“…Vandenberghe et al [8] compared the unloading effect of the Medos microdiagonal rotary blood pump under both continuous and pulsatile modes, and also studied the haemodynamic modes of ventricular assist with the Medos DeltaStream rotary blood pump in continuous and pulsatile modes [7]. In studies of VAD control strategy design, Giridharan & Skliar [9] and Ohuchi et al [10] modulated the speed of the rotary blood pump and produced pulsation of arterial pressure covering the physiological range. However, Shi et al [11] carried out numerical evaluations in a HeartMate III impeller pump and warned that, although modulating the pump rotating speed could produce physiological pressure pulsation, this control mechanism also induced strong regurgitant pump flow, which greatly reduced the pump efficiency.…”