LONG-TERM EVALUATION OF GAS-EXCHANGE AND HYDRODYNAMIC PERFORMANCE OF A HEPARINIZED ARTIFICIAL LUNG - COMPARISON OF 2 DIFFERENT HOLLOW-FIBERPORE SIZES

We compared the performance of a heparinized hollow fiber artificial l ung (Medtronic, Minimax) featuring standard hollow fibers (Group A) an d experimental hollow fibers with a smaller pore size (Group B). Four sheep in each group underwent a veno-venous bypass for 72 hours. Every 6 hours, at 3 different blood flow rates (BFr) (400, 800, 1200 ml/min ), at a constant gas flow rate (Gfr = 4 L/min), and at a constant bloo d inlet PCO2 (45-55 mmHg), we measured the oxygenation performance (O- 2 transfer = VO2 and blood outlet PO2 = PO(2)out), CO2 removal (CO2 tr ansfer = VCO2 and PCO2 outlet = PCO2out) and pressure drop across the device (Delta P). A total of about 50 measurement sets were obtained f or each group at different time points and blood flow rates. Both grou ps showed a good oxygenation performance (PO2out always higher than 20 0 mmHg) and no differences were observed between the two groups (at 12 00 ml/min BFr, the average VO2 of all time points was 47 +/- 15 ml/min in group A and 44 +/- 11 ml/min in group B, mean +/- SD, NS). During the first 24 hours, the VCO2 was higher in Group B than in Group A at each BFr (at 1200 ml/min BFr, 81 +/- 18 vs 67 +/- 20 ml/min, p<0.01), while no differences were observed during the subsequent 48 hours. Thr oughout the entire experiment, VCO2 increased with increasing BFr in b oth groups, (in group B, from 43 +/- 14 ml/min at 400 ml/min BFr, to 7 3 +/- 17 ml/min at 1200 ml/min BFr, average of all time points, p<0.01 ). In both groups the Delta P increased with the increasing BFr, but i t was lower in Group B than in Group A at BFr 800 and 1200 ml/min (at 1200 ml/min BFr, 51 +/- 15 mmHg vs 65 +/- 17 mmHg, p<0.01), and remain ed stable for the entire experimental period.