Gas transfer performance of a hollow fiber silicone membrane oxygenator: ex vivo study.

Based on the results of in vitro studies of many experimental models, a silicone hollow fiber membrane oxygenator for pediatric cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO) was developed using an ultrathin silicone hollow fiber with a 300 microm outer diameter and a wall thickness of 50 microm. In this study, we evaluated the gas transfer performance of this oxygenator simulating pediatric CPB and ECMO conditions. Two ex vivo studies in a pediatric CPB condition for 6 h and 5 ex vivo studies in an ECMO condition for 1 week were performed with venoarterial bypass using healthy calves. At a blood flow rate of 2 L/min and V/Q = 4 (V = gas flow rate, Q = blood flow rate) (pediatric CPB condition), the O2 and CO2 gas transfer rates were maintained at 97.44 +/- 8.88 (mean +/- SD) and 43.59 +/- 15.75 ml/min/m2, respectively. At a blood flow rate of 1 L/min and V/Q = 4 (ECMO condition), the O2 and CO2 gas transfer rates were maintained at 56.15 +/- 8.49 and 42.47 +/- 9.22 ml/min/m2, respectively. These data suggest that this preclinical silicone membrane hollow fiber oxygenator may be acceptable for both pediatric CPB and long-term ECMO use.

Preclinical evaluation of a hollow fiber silicone membrane oxygenator for extracorporeal membrane oxygenator application.

A silicone membrane hollow fiber oxygenator applicable for use as an extracorporeal membrane oxygenator (ECMO) has been developed in our laboratory. This silicone hollow fiber displays astonishing mechanical stability, is barely compressible or stretchable, and assembles easily while maintaining good gas permeability. The priming volume is 140 cc with a surface area of 0.8 m2. This study evaluated the gas transfer performances and biocompatibility of the oxygenator under ECMO and CPB conditions. In vitro studies that were performed at a blood flow rate of 2 L/min, and revealed O2 and CO2 gas transfer rates of 82.35 +/- 0.56 ml/m2/L/min and 38.72 +/- 2.88 ml/m2/L/min, respectively. The commercially available Kolobow (Avecor 1500) oxygenator was used as the control, and had O2 and CO2 gas transfer rates of 53.8 +/- 0.5 ml/m2/L/min and 24.7 +/- 2.0 ml/m2/L/min. To evaluate blood trauma, Normalized Index of Hemolysis (NIH) was measured according to American Society of Testing and Materials (ASTM) standards. The NIH findings were 0.0112 g/100L at a blood flow of 1 L/min, and 0.0152 g/100L at 5 L/min. Three ex vivo experiments, using a blood flow rate of 1 L/min, were performed with venoarterial bypass, and O2 transfer rate and CO2 transfer rate of the oxygenators were well maintained. This indicates that this preclinical silicone membrane hollow fiber oxygenator has superior efficiency, less blood trauma, and is smaller when compared with the only clinically available Kolobow oxygenator.

Development of a silicone hollow fiber membrane oxygenator for ECMO application.

A new silicone hollow fiber membrane oxygenator for extracorporeal membrane oxygenation (ECMO) was developed using an ultrathin silicone hollow fiber, with a 300 microm outer diameter and a wall thickness of 50 microm. The hollow fibers were mechanically cross-wound on the flow distributor to achieve equal distribution of blood flow without changing the fiber shape. The housing, made of silicone coated acryl, was 236 mm long with an inner diameter of 60 mm. The surface area was 1.0 m2 for prototype 211, and 1.1 m2 for prototype 209. The silicone fiber length was 150 mm, and the silicone membrane packing density was 43% for prototype 211 and 36% for prototype 209. Prototype 211 has a priming volume of 208 ml, and prototype 209 has a priming volume of 228 ml. The prototype 211 oxygenator demonstrates a gas transfer rate of 120 +/- 5 ml/min (mean +/- SD) for O2 and 67 +/- 12 ml/min for CO2 under 2 L of blood flow and 4 L of O2 gas flow. Prototype 209 produced the same values. The blood side pressure drop was low compared with the silicone sheet oxygenator (Avecor, 1500ECMO). These results showed that this new oxygenator for ECMO had efficiency similar to the silicone sheet oxygenator that has a 50% larger surface area. These results suggest that the new generation oxygenator using an ultrathin silicone hollow fiber possesses sufficient gas transfer performance for long-term extracorporeal lung support.