Experimental study of air bubbles in a simulated cardiopulmonary bypass system with flow constriction

Abstract

An experimental study is performed to examine the breaking of an air bubble in the flow passage of a simulated cardiopulmonary bypass system by means of a flow constriction. The purpose of the study is to discover a geometry of the flow constriction which is efficient in breaking air bubbles while providing the least resistance to the flow of blood, i.e. to develop a new device for the oxygenation of the blood in extracorporeal circulation.Both plasma and water are used in the study. The use of plasma is to simulate the principal transport properties of the human blood and enable direct visualization of bubbles. Water is used for comparison with plasma to determine the influence of fluid properties on the breaking of bubbles. Several different shapes of flow constriction are tested. It is observed that as a result of rapid changes in the liquid pressure and bubble shape, an air bubble breaks into many bubbles at downstream from the flow constriction. The results are quantatively expressed by the number of baby bubbles vs. the flow rate.It is disclosed that the flask-shape constriction is efficient in breaking air bubbles while providing ideal passage for the flow of blood. The number of baby bubbles is found to increase with an increase in the fluid viscosity.