Preload-Based Starling-Like Control for Rotary Blood Pumps: Numerical Comparison with Pulsatility Control and Constant Speed Operation

Abstract

In this study, we evaluate a preload-based Starling-like controller for implantable rotary blood pumps (IRBPs) using left ventricular end-diastolic pressure (PLVED) as the feedback variable. Simulations are conducted using a validated mathematical model. The controller emulates the response of the natural left ventricle (LV) to changes in PLVED. We report the performance of the preload-based Starling-like controller in comparison with our recently designed pulsatility controller and constant speed operation. In handling the transition from a baseline state to test states, which include vigorous exercise, blood loss and a major reduction in the LV contractility (LVC), the preload controller outperformed pulsatility control and constant speed operation in all three test scenarios. In exercise, preload-control achieved an increase of 54% in mean pump flow () with minimum loading on the LV, while pulsatility control achieved only a 5% increase in flow and a decrease in mean pump speed. In a hemorrhage scenario, the preload control maintained the greatest safety margin against LV suction. PLVED for the preload controller was 4.9 mmHg, compared with 0.4 mmHg for the pulsatility controller and 0.2 mmHg for the constant speed mode. This was associated with an adequate mean arterial pressure (MAP) of 84 mmHg. In transition to low LVC, for preload control remained constant at 5.22 L/min with a PLVED of 8.0 mmHg. With regards to pulsatility control, fell to the nonviable level of 2.4 L/min with an associated PLVED of 16 mmHg and a MAP of 55 mmHg. Consequently, pulsatility control was deemed inferior to constant speed mode with a PLVED of 11 mmHg and a of 5.13 L/min in low LVC scenario. We conclude that pulsatility control imposes a danger to the patient in the severely reduced LVC scenario, which can be overcome by using a preload-based Starling-like control approach.

A Starling‐like total work controller for rotary blood pumps: An in vitro evaluation

“…The undesirable effect of increasing RBP hydraulic work with the power ratio controller during independent contractility increase may reduce the workload of the native heart, limiting the potential for ventricular recovery. Meanwhile, when comparing the Starling‐like controllers of Petrou et al comparison study, although the preload recruitable stroke work controller and Starling‐like flow controller reduced RBP flow during increases in ventricular contractility, the total cardiac output was not maintained at 5.0 L/min. Consequently, both these controllers, are less sensitive to improvement in ventricular function when compared with the SL‐TWC as they do not consider ventricular workload as a feedback.…”

The Importance of Venous Return in Starling‐Like Control of Rotary Ventricular Assist Devices

“…Although not explored experimentally in this study, several previous studies have been published which have hypothesized that the gradient of the VRL will change depending on the opening state of the ventricular output valve. This phenomenon was observed when mapping the VRL via the “system response method.” The system response method involves holding the simulated cardiovascular system at a given state and manually changing pump speed to view the preload response of the OP, then using that path as the VRL for the SLC.…”

Standardized Comparison of Selected Physiological Controllers for Rotary Blood Pumps: In Vitro Study

“…Particularly, two of the implemented controllers (described below) were selected due to their outperformance over another five controllers and the CS operation presented in the comparison study of Pauls et al . The other four controllers were selected due to their clear outperformance over the CS operation that they presented when published , while they offered a reasonable concept variability. For the case of controllers presented in , they have been previously developed in our group and, therefore, we have a deep insight of both, while they have been successfully evaluated in vivo .…”

“… CO , cardiac output; LVDP min , minimum left ventricular diastolic pressure; HR, heartrate; AoP, aortic pressure; R* , systemic resistance; K PF (EDP), scaling factor ; P , pump pressure difference; RPM, maximum minus minimum pump speed; SP, systolic pressure; EDV, end‐diastolic volume; EDP, end‐diastolic pressure; PF, pump flow rate; PS, pump speed; ref, reference; des, desired; e, error between measured and reference signals; CS, constant‐speed operation; IOP, inlet–outlet pressure controller; PF‐EDP, pump flow‐end‐diastolic pressure controller; AI, afterload‐impedance controller; SPPC, suction‐prevention and physiologic controller; SP, systolic‐pressure controller; PRS, preload‐responsive controller; bp, blood pump.…”