Development of a completely closed circuit using an air filter in a drainage circuit for minimally invasive cardiac surgery

The completely closed circuit system is the future direction of cardiopulmo nary bypass because of its compactness and superior biocompatibility. The m ost serious obstacle for clinical application is the sucking of air bubbles into the drainage circuit. The purpose of this study was to remove the air bubbles from the drainage circuit. Infusing 50 ml/min of air bubbles into the drainage circuit of the usual closed circuit, and infusing 50, 100, and 150 ml/min of air into the drainage circuit of a newly developed closed ci rcuit (drainage circuit using an air filter), the number and size of air bu bbles were observed at the outlet of the arterial filter. In the usual clos ed circuit, many air bubbles of over 40 mu m were detected within 5 s at a blood flow of 4 L/min because the centrifugal pump decreased the size of th e bubbles, which then passed through the oxygenator and arterial filter. Ai r bubbles of over 40 mu were not detected in the newly developed closed cir cuit within 5 min at a blood flow of 4 L/min. The removal of air mixed into the completely closed circuit was possible with a drainage circuit using a n air filter that was developed. The clinical use of the completely closed circuit for minimally invasive cardiac surgery (MICS) became possible based on this development.