Optimum control of the Hemopump as a left-ventricular assist device

Abstract

A general framework for designing an optimum control strategy for the Hemopump is described. An objective function was defined that includes four membership functions, each constructed based on the desired values of one of the four members: stroke volume, mean left atrial pressure, aortic diastolic pressure and mean pump rotation speed. The Hemopump was allowed to operate either at a constant speed or at two different speeds during a cardiac cycle. The goal was to maximise the objective function by varying the magnitude and timing of the pump speed. Using a canine circulatory model, it was demonstrated that, in general, different cardiac conditions or different clinical objectives require different operation parameters. For example, when a left ventricle with minor ischaemia was simulated, and the main objective was to increase stoke volume, the objective function was maximised, from a value of 0.877 when the pump was off, to 0.946 when the pump was operated at speed 2 (18 500 revolutions min(-1)). On the other hand, for a severely ischaemic heart, the optimum pump speed became speed 3 (20 000 revolutions min(-1)), which maximized the objective function to 0.943 (from 0.707 when the pump was off). The results also suggest that it is more beneficial to operate the Hemopump at two different speeds during a cardiac cycle (a higher speed during systole and early diastole, and a lower speed during late diastole) than to maintain a constant speed throughout the cardiac cycle.

Synchronized Pulsatile Speed Control of Turbodynamic Left Ventricular Assist Devices: Review and Prospects

“…He et al. performed an in silico study using square‐wave speed profiles. Seven different speed levels in the range of 17 000 rpm to 26 000 rpm, with intervals of 1500 rpm, were considered.…”

Numerical Optimal Control of Turbo Dynamic Ventricular Assist Devices

“…A square-wave speed profile was applied by Bearnson et al [11] and Bourque et al [12] to increase arterial pulse pressure, where the speed profile was not synchronized to the cardiac cycle. Different types of speed profiles, synchronized to the natural cardiac cycle, have been applied in silico and in vitro to analyze their influence on perfusion, pulse pressure and ventricular unloading [13][14][15][16][17][18]. In vivo experiments have been conducted to validate this approach [19,20].…”

Durability improvement of polymer chamber of pulsatile extracorporeal life support system in terms of mechanical change

“…Hence, in order to obtain the CE mark or KFDA approval for these applications, which require its prolonged utilization, in the near future, the long-term reliability or durability testing of the T-PLS is required. Since 1980, reliability tests or optimum control have been conducted for artificial hearts by other research groups [4,6,13,15,22,28,35]. The existing methods of analyzing the reliability of an artificial heart are based on fault tree analysis (FTA) or failure mode and effect analysis (FMEA) [4].…”