Mass transfer characteristics of artificial lungs

An artificial lung is used during cardiopulmonary bypass to oxygenate blood and control blood temperature. The oxygen transfer rate-flow rate characte ristics of three hollow fiber membrane artificial lungs (Sarns Turbo 440, C obe Optima, Dideco Compactflo) were determined in vitro to characterize des ign features. Results are presented as a unique dimensionless relationship between Sherwood number, N-Sh (ratio of convective to diffusive mass transf er), Schmidt number, N-Sc (ratio of momentum to diffusive transport), and R eynolds number, N-Re. (ratio of inertial to viscous forces). This relations hip is a function of device porosity, epsilon, and characteristic device le ngth, xi, defined as the ratio of the mean blood path and manifold length: N-Sh/N-Sc(1/3) . xi (1/2) = phi . (epsilon (1/m) . N-Re)(m) where phi = 0.26 and m = 1.00 for N-Pe < 3,200 and phi = 0.47 and m = 0.64 for N-Pe > 3,200 where N-Pe is the dimensionless Peclet number defined as N -Re . N-Sc. We found good correspondence between the model predictions and in vitro blood oxygen transfer rates. We conclude that this dimensionless a pproach allows us (1) to compare artificial lungs independently, (2) to rel ate water tests to blood, and (3) to predict the oxygen transfer rate of a new artificial lung design.