An oxygenator with a built-in hemoconcentrator. In vitro performance and pre clinical in vivo assessment of the final prototype

To facilitate the handling of cardiopulmonary bypass (CPB) and simplify the circuit, the authors have developed a new membrane oxygenator with a hemofiltration function. The hollow fiber units for gas exchange and hemofiltration were combined in concentric circles in a cylindrical housing. The total priming volume was 190 ml. Because the authors adopted a silicon coated hollow fiber membrane for gas exchange, this oxygenator was completely resistant to serum leakage, even after treatment to make the device hydrophilic. Both units possess a blood-outside perfusion system. Filtered fluid was collected easily through a stopcock mechanism. The oxygen transfer rate was 312 ml/min at a blood flow rate of 6 L/min, and the ultrafiltration rate was 3.5 L/hr at a blood flow rate of 4 L/min with a 25% hematocrit and 200 mmHg transmembrane pressure in an in vitro study. The pressure drop was 62 mmHg at a blood flow rate of 4 L/min. The authors found no adverse effects in an in vivo study using a mongrel dog. In conclusion, this durable, combined device could achieve excellent and simplified hemoconcentration through having all the blood in the unit flow through the hemofiltration portion, and was useful not only in cardiopulmonary bypass during open heart surgery, but also in extracorporeal membrane oxygenation.