Can the oxygenator screen filter reduce gaseous microemboli?

Gaseous microemboli (GME) define small bubbles as < 200 microm in size. GME are reported to increase morbidity after cardiopulmonary bypass (CPB) and cardiac surgery. To prevent intrusion of GME into the systemic circulation during CPB, arterial line filtration is generally recommended. New trends in oxygenator design promote location of arterial filtration as an integral part of the oxygenator housing. The present experimental study aimed to evaluate the GME removal properties of an integrated arterial screen filter in a standard microporous oxygenator. The GME properties of Terumo Capiox FX25 with an integrated arterial screen filter was assessed in an experimental setup and compared with Capiox RX25, in which no arterial screen filter is present. A blood analog prime solution was recirculated using a roller pump at 4 and 6 L per minute flow rate, respectively, through a customized CPB circuit comprising oxygenator, reservoir, and connecting tubing. A controlled volume of air was introduced into the circuit. The GME activity was measured and computed using a Gampt BCC200 ultrasonic device placing one probe at the venous inlet and one other at the arterial outlet of the oxygenator. Transmembrane delta values of GME activity were used to calculate the removal efficacy based on counts and volume of GME. Use of screen filtration reduced the GME volume by 99.1% +/- .1% compared with 98.0% +/- .1% for controls at 4 L/min flow rate (p < .001). At 6 L/min, the reduction was 97.9% +/- .1% compared with 97.0% +/- .1% (p < .001). In contrast, the reduction of GME counts was less effective after screen filtration compared with controls: 89.6 +/- .6% versus 91.4 +/- .4% at 4 L/min and 55.6% +/- 1.6% versus 76.0% +/- 1.4% at 6 L/min, respectively (p < .001). The tested oxygenator with incorporated arterial screen filter reduced GME activity based on the calculated volume at the same time as counts of GME increased.