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Simulation of Left Atrial Pressure and Flow Dynamics Using an Adaptable Control Architecture in a Mock Circulatory Loop

For the purposes of analyzing the possible impact of external factors on the performance and reliability of a left ventricular assist device (LVAD), a pulmonary simulator would be critical for in vitro use within a mock circulatory loop (MCL). To accurately reproduce the conditions within the pulmonary system, a pulmonary simulator should not only account for the capacity of the pulmonary system to supply flow at given pressures, but also consider the systemic outflow dynamics. This would allow for an accurate pressure and flow rate return feed back into the left ventricular portion of the MCS, i.e. the initial conditions of the left heart. Utilizing Windkessel modeling techniques, a computational model was developed using Simulink® Simscape that generates the left atrial pressure waveform for given aortic conditions, systemic variables, and pulmonary factors. The adaptability of this model provides the ability to reproduce a wide range of circulatory conditions without the limitations of a dedicated hardware platform. Following a verification and validation (V&V) model, a closed loop, PID controlled, hydraulic system was developed utilizing Simulink® Simscape. Once this simulation was completed, testing of the pulmonary simulator was conducted on the MCL. Simulink® Real-Time was used to control the in vitro system during verification studies of the pulmonary simulator, as well as, validation of the control architecture used to simulate pulmonary performance. Empirical verification of the pulmonary simulator performance and validation of the control architecture support this modeling and control method as an effective means of reproducing pulmonary pressure and systemic outflow.