Modelling of plasma-separation through microporous membranes.

Available mathematical models of ultrafiltration have been used to predict changes in maximum plasma filtration rate with wall shear rate for given filters and blood properties. We have done many plasmapheresis experiments in vitro, using hollow-fiber filters (500-1000 cm2) and fresh bovine blood collected on ACD or heparin. The comparison between predicted and experimentally obtained filtration rates was good for models based on the concentration polarization theory and lift velocity theory. In other experiments with pulsatile inlet flow we found that plasma filtration rate increased by 20 to 50% compared to non-pulsatile conditions. These results are in good agreement with the modified model of ultrafiltration incorporating pulsating flow. This paper presents relationships between plasma filtration velocity (steady and pulsating flow) and hemolysis limit as a function of wall shear rate and filter size.