In vitro evaluation of the hydraulic permeability of polysulfone dialysers

An in vitro set-up has been designed to study the hydraulic permeability of hollow fiber dialysers. Forward and reverse dialysate ultrafiltration were determined using both sterile dialysers and samples with a protein layer settled on the membrane (Fresenius F6, F8, F60 and F80). The ultrafiltration coefficient K-UF (ml/h.mmHg) was calculated as the ratio of volumetrical flow (Q(UF)) and transmembrane pressure (TMP) measurements. The protein layer on the membrane was induced either by recirculating human plasma through the dialysers (in vitro) or by a standard hemodialysis session (in vivo). K-UF is largely independent of TMP up to 600mmHg (low flux) and 60mmHg (high flux) for forward and reverse flow. In sterile dialysers, backfiltration yields a significantly different K-UF except for the F80. An in vitro induced protein layer on the membrane decreases K-UF 15-30% (forward) and 4-12% (backward) in low flux and 45-70% (forward) and 65-73% (backward) in high flux dialysers.