Steady-State Model of Pressure-Flow Characteristics Modulated by Occluders in Cardiopulmonary Bypass Systems

Cardiopulmonary bypass is a complex procedure that involves the maintenance of heart and lung functions using an external system during cardiac surgery. It is prone to significant human errors, which are mainly caused by inappropriate occluder operation that controls the perfusion balance by adjusting flow rates. Hence, there is a requirement for automatic occluder control; however, the relationship between occluder operation and flow rates remains unclear. The aim of this study is to use a steady-state model to evaluate the influence of occluder control on the flow and pressure of a cardiopulmonary bypass system. Perfusion experiments were performed using Newtonian (glycerin solution) and non-Newtonian (erythrocyte turbid solution) fluids to investigate the pressure-flow characteristics modulated by the occluder. We also visualized the fluid to verify the validity of the measurement data. Based on these experimental data, an exponential occlusion-pressure model is derived to express the relationships between the opening ratio of the occluder and flow rate. Estimation is then achieved by combining the occlusion-pressure model with the linear pressure-flow model. Results reveal that the combined model fitted the perfusion experiment data well for the venous and arterial line side (R
²
= 0.946 and 0.985, respectively; p <; 0.01 ). Further, leave-one-out cross-validation and Bland-Altman analysis confirmed that the combined model could predict flow rates accurately with minimal proportional and bias errors. Therefore, the proposed model can serve as a basis for the further development of cardiopulmonary manipulation systems.