A DURABLE HIGH-PEFORMANCE THROMBO-RESISTANT OXYGENATOR MADE OF NOVEL HOLLOW FIBER MEMBRANE AND HEPARIN-BINDING MATERIAL

Abstract

We have developed a durable high-performance thrombo-resistant oxygenator for prolonged use. The extraluminal flow type oxygenator consists of novel smaller-diameter polyolefin-made microporous hollow fiber membrane (outer diameter: 205 μm) which effectively augments gas exchange capacity due to larger membrane area and more effective convective mixing of blood among the fibers. In this membrane, micropores are blind-ended to form a thin dense layer (thickness <0.2 μm), and direct blood-gas contact is virtually eliminated to prevent plasma leak in protracted use. Furthermore, the current elaboration successfully enhanced oxygen permeability of the membrane from 40 × 10−5 to 120 × 10−5 m3(STP)/m2/sec/mmHg by controlling the material's crystallinity at manufacturing process and increasing the porosity without compromising its characteristic structural feature. The compact prototype oxygenators (membrane surface area: 1.27 m2, priming volume: 240 ml) were manufactured using the preceding membrane (Oxy-P) and the current membrane with high oxygen permeability (Oxy-C), respectively. In addition, the entire blood-contacting surface of Oxy-C was treated with newly developed antithrombogenic heparin-binding material (Oxy-H). Gas exchange performance of these oxygenators was evaluated in in vivo cardiopulmonary bypass study using an adult goat. Oxygen transfer rates at 1.0 gas/blood flow ratio in Oxy-P, Oxy-C, and Oxy-H were 162, 175, and 185 ml/min at 3 L/min blood flow, and 249, 293, and 265 ml/min at 5 L/min blood flow, respectively. Carbon dioxide removal rates at the same condition were 73, 127, and 152 ml/min at 3 L/min blood flow, and 221, 240, and 229 ml/min at 5 L/min blood flow, respectively. Thus, the use of higher permeability membrane appreciably increased gas exchange capacity, while the newly developed heparin-coating treatment did not exert any untoward effect We conclude that this compact oxygenator with high durability and antithrombogenicity possesses sufficient capacity for the use as ECMO and percutaneous cardiopulmonary support.