96 HOURS EVALUATION OF A COMPACT GAS EXCHANGER FOR AMBULATORY ARTERIO-VENOUS CARBON DIOXIDE REMOVAL (AVCO2R)

Abstract

With the goal of developing an ambulatory AVCO2R system, we have tested the performance characteristics of a downsized gas exchanger (1.3 m2, uncoated x30–240 Celgard hollow fibers) with an injection-molded polycarbonate housing (MC3, Inc., Ann Arbor, MI) in a 96 hour healthy sheep model. Methods: The gas exchanger was attached from the carotid artery (12F) to the jugular vein (14F) of adult sheep (n=3) by percutaneous cannulae. ACT was maintained between 160–240 Sec by continuous intravenous heparin. Hemodynamics, blood gases, CBC, and CO2 removal were recorded at 6th, 24th, 48th, 72nd and 96th hour. CO2 removal was measured at a constant blood flow rate (Qb) of 1 L/min with varying sweep gas (Qg) from 1 to 15 L/min, and at constant Qg of 5 L/min with varying Qb from 0.5 to 1.5 L/min to determine the capacity of CO2 removal. Results: Hemodynamics and blood hemoglobin level remained stable throughout the study. CO2 removal utilizing this downsized gas exchanger varied with changes in device blood flow and sweep gas flow rate. CO2 removal with Qb=1L/min and Qg=5L/min was 107±11, 92±13, 90±15, 71±28 and 81±23 mL/min at 6, 24, 48, 72 and 96 hours, respectively. At Qg=5L/min, CO2 removal by the gas exchanger directly correlated with increasing blood flow rate (R2=0.997, P<0.001). During autopsy, clotting was observed in the distal end of all gas exchange devices. Conclusion: This downsized gas exchanger achieves stable, near total resting CO2 removal for 96 hours with a simple arteriovenous shunt.