Application of a hybrid model to continuous flow pump investigation

Objectives: Continuous flow pumps (CFP) are widely used and differ from each other in types, connection and performance. Circulatory and ventricular conditions too play a role in pump performance. The number of variables involved makes modelling an appealing tool to study pump performance in different patient's conditions and to support clinical decision. This work aims at developing a circulatory model merging a computational model (CM) with a CFP working in its own environment. In this way it is possible to investigate the CFP effects on variables calculated by the computational model but influenced by the pump. Methods: The lumped parameter CM consists of left and right hearts, systemic, pulmonary and coronary circulation. The CFP is represented by an electrical model realised using operational amplifiers. The pump speed and the slope of the pressure-flow characteristics can be controlled to simulate different pump types. Pump performance was analyzed considering circulatory (Cardiac Output-CO, left atrial pressure-LAP, aortic pressure-AOP) and ventricular variables (ESV and EDV) against ranges of left ventricular Emaxl (0.5-2.5-3.5 mmHg·cm-3) and stiffness (30-60 cm3·mmHg-1). All experiments were conducted comparing the selected variables before and after pump activation. The pump was connected between left atrium and aorta. Results: Chosing maximum pump speed and Emax=3.5 mmHg·cm-3, CO, LAP and AOP variations are remarkable: 45%, -300% and 73%, respectively. The pump flow shape is influenced by the pressure variations across the pump head. Different ventricular and circulatory conditions produce remarkably different effects and it is possible to identify dangerous situations (suction). Conclusions: This work demonstrates the possibility to merge a CM with a device working in a different environment. The model provides a platform to produce stable and repeatable circulatory conditions. The CM will be connected to a real device using the technology developed in the frame of EU SensoART project.