Control strategy to enhance pulmonary vascular pulsatility for implantable cavopulmonary assist devices: A simulation study

Abstract

ObjectiveFontan failure can be potentially addressed with an implantable pump in the cavopulmonary junction (cavopulmonary assist device, CPAD) to replace the missing subpulmonary power source. Fontan pulmonary circulation lacks pulsatility due to the absence of the right ventricle, which has adverse physiological consequences. CPAD can augment pulmonary flow and improve Fontan hemodynamics. However, CPAD operating at a constant pump speed does not provide pulmonary arterial pulsatility, provide physiologic flow to match cardiac demand, or avoid suction. To overcome these limitations, a sensorless control strategy for CPAD is proposed. MethodsCPAD pump speed measurement, an intrinsic pump parameter, was used to estimate cavopulmonary pressure head (CPPH). A gain scheduled proportional-integral controller alternates CPPH between high/low setpoints (CPPHHr/CPPHLr) that generates pulsatility, while simultaneously adapting to cardiac demand and avoiding suction. Computer simulations were performed to quantify the overall performance of the proposed algorithm at rest and exercise, rapid transition from exercise to rest, and doubling of the vena caval resistance. The performance was compared against CPPH measured using pressure sensors, and a constant pump speed control strategy. ResultsThe sensorless algorithm generated a pulmonary vascular pulsatility of approximately 10 mmHg, and matched the cardiac demand at rest and exercise. The frequency of pump speed modulation was 10–15 cycles per minute and no suction was observed. Conclusion and significanceThe sensorless strategy outperformed constant CPAD speed control algorithm for improvement of pulmonary vascular pulsatility and physiologic perfusion. Further validation is needed using mock loop and animal tests.