In Vitro Evaluation of Control Strategies for an Artificial Vasculature Device

Abstract

Ventricular assist devices (VADs) have been used successfully as a bridge to transplant in heart failure patients by unloading ventricular volume and restoring the circulation. An artificial vasculature device (AVD) that may better facilitate myocardial recovery than VAD by controlling the afterload seen by the ejecting heart is being developed. The AVD concept is to enable any user-defined input impedance (IM) with resistance (R) and compliance (C) components. In this study, a pulse duplicator was used to test the efficacy of the AVD concept for two control strategies in an adult mock circulation: (1) R-C in series and (2) 2-element Windkessel (R-C in parallel) using instantaneous impedance position control (IIPC) to maintain a desired value or profile of R and C. In vitro experiments were performed and the resulting cardiovascular pressures, volumes, flows, and the afterload (R and C) seen by the LV during ejection for simulated cardiac failure were recorded and analyzed. Our results indicate that setting the AVD to lower IM reduced LV volume and pressure, restored LV stroke volume, and increased coronary flow. The IIPC control algorithms are better suited to maintain any instantaneous IM or an IM profile, but are susceptible to measurement noise.

An advanced mock circulation loop for in vitro cardiovascular device evaluation

“…The physiologic hemodynamic waveforms produced by the MCL were achieved through high‐frequency control of the electropneumatic regulators which control left and right ventricular contraction, thus avoiding the square‐shaped ventricular pressures often seen in other systems . Meanwhile, simulation of the ventricles using vertically placed PVC pipes with pneumatic actuation and passive filling prevented negative ventricular pressures as seen in other systems that use flexible sacs as heart chambers or piston‐driven ventricles .…”

Simulador pediátrico InCor: desenvolvimento de um modelo hidráulico do sistema circulatório pediátrico com ajustes automatizados de pressões.

“…Foram obtidas formas de ondas das pressões e fluxos e os loops-PV para as três condições simuladas. A precisão dos resultados obtidos fez com que este simulador fosse utilizado em estudos posteriores(39,48).A partir da metade da década de 2000 começaram a surgir novos projetos de DAVs pediátricos proporcionando avanços no desenvolvimento de simuladores da circulação pediátrica(27,28). Um estudo que exemplifica esta tendência foi apresentado porGoodwin et al (2004) (27) onde os parâmetros de um modelo previamente caracterizado para simulação da circulação sistêmica de adultos foram redefinidos para modelar pressões e fluxos encontrados em recém nascidos.…”