The Implantable Fuzzy Controlled Helmholtz‐Left Ventricular Assist Device: First In Vitro Testing

Abstract

To perform first experimental tests for validation of a new left ventricular assist device (LVAD) with a high efficiency energy converter, a new pump design and a novel type of perfusion control, a functional labtype, were manufactured. With a stroke volume of 65 ml, a total pump housing volume of 450 ml (including valves and connectors), and a weight of 430 g, it is one of the smallest and lightest implantable pulsatile electromechanical LVADs. Pulsatile operation is generated by a special reduction and displacement gear which transforms a uniform rotational movement of a sensorless. electronically commutated DC motor into a translatory pusher plate movement. A prolonged duration for filling (60% of the cycle time) supports full-empty pumping and consequently a high overall pump efficiency. Active adaptation of output flow to organ perfusion demand is achieved by changing the rotational speed of the motor by means of a sensorless fuzzy controller, which detects preload and afterload induced effects at the motor current input. First in vitro test results obtained within a circulatory mock loop that simulates physiological preloads and afterloads are presented. They comprise preload sensitivity and the function of the novel perfusion controller as well as preload and afterload related flow data. The results prove the feasability of the energy conversion with the novel gear and control concept for an implantable electromechanical pulsatile LVAD.

In vitro evaluation of multi‐objective physiological control of the centrifugal blood pump

“…The fuzzy control system has characteristics appropriated for assistance circulatory applications. 6,11,13,14,39,40 Figure 5 shows a membership function configuration for each variable of FzC. Membership function is adequately sets for harmonious and safe operation.…”

“…10 Others works propose a fuzzy system as a controller to adjust LVAD speed with preload and afterload response. [11][12][13][14] Volkron et al designed a control algorithm to obtain a linear relationship between heart rate (HR) and pump speed. 15 Gao et al show a numeric simulation of an anti-suction control based on blood assistant index of ventricle unloading.…”

“…Computer simulations, in vitro and in vivo tests point to the effectiveness of the fuzzy control system. 10,11,[18][19][20] Controllers aimed at physiological performance, but the evolution of the patient's clinical condition was not part of their rules.…”

Estimation of Filling and Afterload Conditions by Pump Intrinsic Parameters in a Pulsatile Total Artificial Heart

“…This control algorithm should be able to monitor and react to (i) changes in preload, (ii) changes in afterload, and (iii) a physiological imbalance between systemic and pulmonary flow. Other systems use similar methods but based on current consumption (13,14). Hemodynamic parameters, including inlet and outlet blood pressures and blood flows, can be measured by implanted blood pressure and flow sensors (5).…”

“…The left ventricular filling and arterial pressure are estimated from the measured position of the actuator, motor speed and motor voltage (11,12). Other systems use similar methods but based on current consumption (13,14). These methods only estimate the hemodynamic state of the systemic circulation.…”