Flow distributions in hollow fiber hemodialyzers using magnetic resonance Fourier velocity imaging.

Abstract

Distribution of flow within the hollow fibers and the dialysate compartment of hemodialyzers is difficult to measure; previous work has suggested that flow distributions may be non uniform. Magnetic resonance Fourier velocity imaging was used to determine flow distributions within the hollow fibers and dialysate compartment of three commercial hemodialyzers (CA170, CT190, and F60A). Distilled water was pumped without pulsatility through the hollow fibers and the outflow was circulated in a countercurrent direction through the dialysate compartment. Steady state flow distributions were determined simultaneously in both directions using input flow rates of 300 and 600 ml/min. Flow distributions within the hollow fibers were relatively uniform in most hemodialyzer cross sections, approximately Gaussian, and similar for all hemodialyzers. Flow distributions in the dialysate compartment were non uniform and skewed to high flow rates. High flow in the dialysate compartment was largely outside the fiber bundle for the CA170 and CT190 hemodialyzers. Local regions containing both low flow within the hollow fibers and high flow in the dialysate compartment were observed for the F60A hemodialyzer, and these regions became more prominent at a flow rate of 600 ml/min. The results of this study demonstrate that flow distributions within the hollow fibers and dialysate compartment of hemodialyzers can be simultaneously determined using magnetic resonance Fourier velocity imaging. It is concluded that the distribution of flow within the hollow fibers of hemodialyzers is relatively uniform but in the dialysate compartment it is not uniform and depends upon hemodialyzer design.