Gaseous Emboli Removal Efficiency in Arterial Screen Filters: A Comparative Study

____________ _ Seven commercially available arterial filters were evaluated for their effectiveness in removing gaseous emboli produced by various sources. All filters were of the screen type and ranged from 2040 micron pore size. The first phase of the study consisted of an appraisal of carbon dioxide flushing to facilitate priming. Two filters of each type were used. The first filter was primed without a carbon dioxide flush. The second filter was flushed with carbon dioxide. Immediately after priming, microemboli were monitored distal to the filters for 10 minutes at 6 LIM in. In the second phase each filter's capability of removing gaseous emboli when used in conjunction with a bubble oxygenator was evaluated. Microemboli were alternately monitored pre and post filter at fluid flow rates ranging from I to 6 L/Min. At each liter of fluid flow rate the gas:fluid ratio was varied from I: I to 3: I. In the third phase of the study, the efficacy of each filter in removing varying amounts of room air was evaluated. Boluses of room air ranging from I to 50 cc. were injected proximal to the filter with microembolism monitoring distally. Injections were made at flow rates ranging from I to 6 L/Min. Although carbon dioxide flushing does facilitate priming the filters, it does not reduce microemboli counts distally. Gaseous emboli removal rates Please direct communications to: Ronald J. Massimino, 106 Moorefield St., Providence, RI 02909. Received 10/82 Revised 2/83 Accepted 3/83 ranged from 69.6 to IOO% when used in conjunction with a bubble oxygenator. Air emboli activity distal to the filter after air injections ranged from 0 to 9I ,000 counts/L of fluid flow. IntroductioiL. ___________ _ It has been documented by ultrasonic technique that the simplest extracorporeal circuits contain microemboli .1.2 The effect of microbubbles in the circulation is not clearly understood. However, there has been a substantial body of evidence accumulated incriminating microemboli as a cause of tissue damage following cardio-pulmonary bypass.3.4 Clinically recognizable effects are seen principally in the form of visual field defects, central nervous system dysfunction and respiratory distress. 6.7-8 It has also been noted that patients 65 years of age and older have a higher incidence of cerebrovascular accidents associated with cardiopulmonary bypass. 5 This may be due to their decreased tolerance to the effects of microemboli. Methods and Materials: ________ _ The circuit consisted of a Harvey H -I500 oxy. b genator•, a Bentley Q-220 cardiotomy reservOir , a Stockert modular pumpc, and polyvinyl chloride tubing with compliment connectors and other ancillary hardware (Figure I). The system was primed with 0.9% sodium chloride solution. The oxygenator which was utilized for microemboli produc' William Harvey, Santa Ana, CA 92705 h Bentley Labs Inc., Irvine, CA 92714 ' Co be Labs Inc .. Lakewood, CO 80215 Volume 15, Number 2. 1983 The Journal of Extra-Corporeal Technology 25