Bubble tracking through computational fluid dynamics in arterial line filters for cardiopulmonary bypass

Gaseous embolism is still a concern in cardiopulmonary bypass, and the use of arterial line filters (ALFs) is widespread because of their recognized role in increasing safety. Currently, the methods used for the optimization/evaluation of ALF designs are based on a trial-and-error approach. In this work, we propose a method to objectively assess the air-handling capabilities of ALFs, using computational fluid dynamics (CFD) simulations to track the trajectory of large numbers of bubbles traversing the device under examination. We applied the CFD method to ALF prototypes, whose design featured the classical purge/screen configuration, to establish the relative roles of the bubble-trap and bubble-barrier deairing effects. Simulations were run at the maximum rated blood flows. Clusters of hundred bubbles in the micro- to macroembolic size range (10-1,000 microm diameter) were tracked. The results quantified the relative amount of bubbles whose fate is either to reach the purge line or to be intercepted by the filter screen. For microbubbles, the analysis detailed how the screen barrier is exploited, mapping the percent distribution of the intercepted bubbles along the screen surface. We conclude that the method proposed increases knowledge and awareness in designing an optimal exploitation of the filtration mechanisms involved in ALFs.