Design and evaluation of a new, low pressure loss, implantable artificial lung

The authors designed and tested an artificial lung intended for intrathoracic implantation as a bridge to lung transplantation in chronic pulmonary insufficiency or as an alternative in the treatment of advanced acute respiratory failure. The prototype devices are comprised of 380 microns outer diameter polypropylene matted fibers with a blood path length of 3.5 cm, frontal area of 128 cm2, void fraction (porosity) of 0.53, and surface area of approximately 2.2 m2. Blood flow is external and approximately perpendicular to the fiber bundle, which fits in an extruded, flexible polyethylene terephthalate housing. Inflow and outflow anastomoses are made to the pulmonary artery and the left atrium, respectively, thereby avoiding a prosthetic blood pump. Inlet and outlet gas lines exit through the chest wall. Nine in vitro experiments of oxygen (O2) transfer performance by the device, with water, initially were done. Our previously described semiempirical mathematical model of convective O2 transfer in cross-flow, hollow fiber membrane lungs was applied to the results from the water tests to predict the transfer rates at any set of blood conditions. Five in vitro blood tests were conducted using a single-pass technique to evaluate O2 and carbon dioxide (CO2) transfer rates, measure pressure losses, and compare predicted and measured O2 transfer rates. O2 transfer rates of 150-200 ml/min, and CO2 transfer rates exceeding 200 ml/min, could be achieved at blood flow rates as great as 4 l/min. Pressure drops of approximately 10-20 mmHg were observed at blood flow rates of 2-4 l/min. Preliminary results of device implantation in two pigs indicate the feasibility of achieving clinically significant O2 and CO2 transfer rates with a low blood-side pressure loss.