Hemolysis reduction in plasmapheresis by module design: operating with pulsed flow filtration enhancement

This study is an investigation into the effects of module design on hemolysis levels during the filtration enhancement of plasmapheresis using pulsed blood flow. Two polypropylene hollow fiber modules (F1 and F2) were compared under steady and pulsed flow conditions. The fiber lengths and membrane areas of the respective filters were 136 mm, 0.1 m2 and 226 mm, 0.25 m2 and were used at wall shear rates of 400 and 600 s-1. Fresh citrated bovine blood was circulated at 90 ml/min through their fibers with permate and retentate being recirculated. Plasma samples were analysed by the Cripps method to obtain the mean free hemoglobin concentration. A comparison of the average hemoglobin released with time per fiber, and per unit length allowed an assessment of the effects of fiber length and shear rate on hemolysis levels. It was concluded that a reduction in area and fiber length would reduce hemolysis levels and design equations are suggested to find the optimum length.