DEVELOPMENT OF A LOW-FLOW RESISTANCE INTRAVENOUS OXYGENATOR

A potentially attractive support device for patients with acute respir atory failure is an intravenous membrane oxygenator. One problem, howe ver, is that the membrane surface area required for sufficient gas exc hange can unduly increase vena caval pressure drop and impede venous r eturn. The purpose of this study was to design and develop an intraven ous oxygenator that would offer minimal venous flow resistance in situ . The device uses a constrained fiber bundle of smaller cross sectiona l size than the vena cava so as to effect an intentional shunt flow of venous blood around the fiber bundle and reduce the venous pressure d rop caused by the device. A pulsating balloon within the fiber bundle redirects part of this shunt flow into reciprocating flow in and out o f the fiber bundle. This offers dual advantages: 1) Blood flow through the fiber bundle is mainly perpendicular to the fibers; and 2) the re quisite energy for driving flow comes largely from the pneumatic syste m pulsating the balloon, not from a venous pressure drop. In this mode a full length device with a 2 cm fiber bundle in a 2.5 cm blood vesse l would offer a pressure drop of only a few millimeters of mercury. Th e use of constrained fiber bundles requires good uniformity of fiber s pacing for effective gas exchange, Several prototypes have been fabric ated, and CO2 and O-2 exchange rates of up to 402 and 347 ml/min/m(2) have been achieved during acute animal implantation.