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

Hidenobu Takahashi,Zu Soh,Toshio Tsuji

doi:10.1109/access.2020.3043470

Abstract

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 ). 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.

Highlights

Cardiopulmonary bypass (CPB) is a procedure that involves the temporary replacement of heart and lung functions for the maintenance of systemic circulation during cardiac surgery
To prevent a decrease in blood pressure owing to abrupt blood removal at the start of CPB [2], in addition to air embolisms owing to low blood retention levels [3], it is necessary to minimize human error and meticulously carry out the CPB procedure
In this study, we model the relationship between the occluder operation amount and flow rate, which can provide a basis for the control system

Summary

Introduction

Cardiopulmonary bypass (CPB) is a procedure that involves the temporary replacement of heart and lung functions for the maintenance of systemic circulation during cardiac surgery. CPB drains blood from the right atrium and bypasses the circulation of the heart and lungs. This bypass perfuses blood into the systemic circulation from the aorta after the gas exchange in the oxygenator. A CPB operator is required to carry out delicate operations for the prevention of significant variations in perfusion pressure and to ensure that the arterialand venous-line side flow rates are equal. During the first CPB procedure by Gibbon [4], a safety sensor was installed in the reservoir to monitor the perfusion balance between the arterial- and venous-line sides for human operation support, as is currently common practice. Complex CPB operations require simplification, automation, or both for the prevention of human error [7, 8]

Objectives

Methods

Results

Discussion

Conclusion