Abstract
The completely closed circuit system is the future direction of cardiopulmonary bypass because of its compactness and superior biocompatibility. The most serious obstacle to its clinical application is sucking of air into the drainage circuit. To overcome this problem, we have developed a new air filter for the low pressure drainage circuit. This filter consists of silicon-coated hollow fibers. Serum leakage cannot occur in these hollow fibers. Blood flows outside of the hollow fibers, and air bubbles entering the drainage circuit are sucked out through the hollow fibers by a strong negative pressure, 650mmHg, applied inside the hollow fibers. Three prototypes were made, and in vitro evaluation was performed in a mock circulation. Effectiveness of air removal was evaluated macroscopically and by using an ultrasound bubble detector. Prototype 3 (membrane surface area; 0.95m2, priming volume; 90ml, pressure drop; 64mmHg at a blood flow rate of 6L/min) completely removed the air in the water irrespective of the size of air bubbles and amount of air and water flow rate. Although air in the blood was also completely removed macroscopically, a slight amount of mi crobubbles was detected. In conclusion, the concept of using a hollow fiber and negative pressure for a reliable and effective air filter in the drainage circuit seems to be promising, and further improvement of the design and specifications will be continued.
