Filtration experiments through 5 or 3μ Nuclepore membranes are often performed in order to assess the so-called erythrocyte deformability. The relation between this parameter and the RBC filterability is not straightforward. A simple theoretical treatment relating filtration index (as determined by the initial flow rate method) to the average RBC flow resistance through an average pore is presented. In order to deduce the average RBC transit time through the membrane from the initial flow rate data, the suspension hematocrit change after filtration has been determined. The calculated average transit time is comparable to experimental values, as determined by Kiesewetter et al. with the single pore technique.
