SMALL INTRAPULMONARY ARTERY LUNG PROTOTYPES - MATHEMATICAL-MODELING OF GAS TRANSFER

Two diffusion models have been developed to analyze gas transfer data previously measured in an intravascular artificial lung consisting of a central gas supply catheter from which are tethered a large number o f blind-ended microporous fibers of equal length. A convective-diffusi on model (CD) describes the countercurrent transfer of a binary gas pa ir when gas is supplied at constant pressure conditions, and a well mi xed (WM) cycled pressure model predicts transfer when the gas supply p ressure is time cycled between compression and vacuum conditions. Regr ession of gas to gas and liquid to gas excretion data with the CD mode l resulted in estimates of the liquid phase mass transfer coefficient k(Al). Because these values were intermediate between the k(Al) expect ed for flow parallel to a cylinder and for flow normal to a cylinder, gas transfer was influenced by both the tethered region of the fiber t hat was nearly perpendicular to the axis of the test section and the f ree end of the fiber that rested along the wall of the test section. W ith a time cycled gas supply pressure, the enhanced carbon dioxide and oxygen excretion predicted by the WM model was similar to the data, b ut a loss in transfer efficiency with fiber length was not accounted f or by the theory.