Investigation of the cleaning effect by the intermittent backfiltration in diafilters with polysulfone and polymethylmethacrylate membranes.

An intermittent infusion during dialysis therapy across the membrane by backfiltration is expected to have a cleaning effect on the membrane in addition to stabilizing blood pressure. In this study, the effect of backfiltration infusion on the solute removal performance was investigated for both diafilters with polysulfone (PSf) and polymethylmethacrylate (PMMA) membrane in vitro experiment using bovine whole blood. To clarify the infusion method with a high cleaning effect, the infusion was performed under two conditions for dialysate flow: countercurrent and parallel flow to blood flow, aiming to induce backfiltration at different area in a diafilter. A scanning electron microscope (SEM) and a scanning probe microscope (SPM) were used for evaluation of the degree of fouling on the membrane after experiments. Although intermittent backfiltration did not show any effect on the removal efficiency of creatinine and inulin, it was slightly effective in maintaining protein permeability under certain conditions. SEM observations and SPM measurements revealed that protein adsorption to the membrane caused the macropore blocking, and the fouling was partly removed by intermittent infusion primarily in areas where backfiltration mainly occurs. In conclusion, backfiltraion had an effect on resolving fouling and recovering solute removal performance for both membrane materials; however, its effect was limited.