FLOW VECTORIAL ANALYSIS IN AN IMPLANTABLE LUNG

Abstract

An implantable lung would be a useful device to support patients awaiting lung transplantation. A suitable device must offer low resistance and adequate gas exchange, be non-thrombogenic. These requirements are largely a function of device geometry. Using a CAD system and the requirements of a membrane surface area of 1.5m2 and an inlet outlet port distance of 12cm, we designed ten models that varied in their other dimensions. Computational fluid dynamics (CFD) software was applied to the models to determine which minimized regions of low velocity. A prototype built to these specifications was used in an in-vivo experiment to verify the CFD predictions. The prototype was placed in parallel to the native pulmonary circulation for 120min while the ACTS were kept between 110–120s and device flow was maintained between 1.5–2.5L/min. Examination of the prototype confirmed a correlation between predicted areas of low flow and thrombus formation. Although nearly identical low flow velocity conditions exist at both the inlet and outlet ports, thrombus formation occurs only near the outlet port. This finding agrees with detailed vectorial analysis, which predicts a more complex flow pattern near the outlet port. While near the inlet port flow vectors are nearly parallel, near the outlet port flow vectors collide. The addition of microflow vectorial analysis to flow velocity predictions allows for improved accuracy in predicting regions at risk of thrombosis.