Efficiency of an air filter at the drainage site in a closed circuit with a centrifugal blood pump: An in vitro study

In a closed circuit with a centrifugal blood pump, one of the serious obstacles to clinical application is sucking of air bubbles into the drainage circuit. The goal of this study was to investigate the efficiency of an air filter at the drainage site. We used whole bovine blood and the experimental circuit consisted of a drainage circuit, two air filters, a centrifugal blood pump, a membrane oxygenator, a return circuit, and a reservoir. Air was injected into the drainage circuit with a roller pump, and the number and size of air bubbles were measured. The air filter at the drainage site could remove the air bubbles (>40 μm) by itself, but adding a vacuum removed more bubbles (>40 μm) than without vacuum. Our results suggest that an air filter at the drainage site could effectively remove air bubbles, and that adding the filter in a closed circuit with a centrifugal blood pump would be safer.