THE INFLUENCE OF THE DIALYSATE FLOW-RATE ON HOLLOW-FIBER HEMODIALYZERPERFORMANCE

The clearance characteristics of two sizes of hemodialyzers (0.9 m(2) and 1.5 m(2)) from the same range of products have been studied over t he dialysate flow range of 500-3,000 ml/min to establish the device's overall mass transfer resistance characteristics. The results obtained demonstrate a difference in the overall mass transfer resistance whic h is most marked at the commonly used dialysate flow rate of 500 ml/mi n. This difference suggests that the increase in size results in the i ntroduction of flow imperfections which reduces the benefit that might be gained by the use of a larger surface area. Results established in dicate a reduction in the overall mass transfer resistance with an inc reasing dialysate flow rate. This reduction is attributed to the prese nce of turbulence in the dialysate pathway at higher flow rates. The p resence of such turbulence was confirmed by visual inspection of the d ialyzer after the completion of the study when it was noted that the o riginal well-ordered configuration present in a new dialyzer had been substantially disturbed. Correlation of the dialysate flow rate with o verall mass transfer resistance by the use of a Wilson plots indicates a nonlinear relationship. This nonlinearity is attributed to a nonful ly developed turbulent flow profile in the dialysate pathway.