Experimental evaluation of flow and dialysis performance of hollow-fiber dialyzers with different packing densities

Abstract

The dialyzer housing structure should be designed in such a way that high dialysis performance is achieved. To achieve high dialysis performance, the flow of the dialysis fluid and blood should be uniform, without channeling and dead spaces. The objective of this study was to evaluate the effect of fiber packing density on the flow of dialysis fluid and blood, and on the dialysis performance of a hollow-fiber dialyzer at defined flow rates for blood (Q (B) = 200 mL/min), dialysis fluid (Q (D) = 500 mL/min), and filtrate (Q (F) = 0 mL/min). We measured Q (D), Q (B), and solute clearance for 3 test dialyzers with dialyzer housing different diameters. To evaluate the flow of dialysis fluid and blood, we measured the residence time of the dialysis fluid and blood in the test dialyzers by use of the pulse-response method. We also measured the clearances of urea, creatinine, vitamin B(12), and lysozyme to evaluate the dialysis performance of the test dialyzers. At packing densities ranging from 48 to 67%, higher packing densities and lower housing diameters of the dialyzer resulted in higher dialysis performance because the dialysis fluid and blood entered the hollow-fiber bundle smoothly and, hence, increased contact area between the dialysis fluid and the blood led to better dialysis performance.

How can dialyzer designs improve solute clearances for hemodialysis patients?

“…15 To improve dialysate flow within the dialyzer, some manufacturers introduced mechanical spacers between the fibers. Packing the capillaries tightly together potentially reduces the space between the fibers limiting dialysate flow and dialyzer clearances, particularly at lower dialysate flow rates.…”

“…Packing the capillaries tightly together potentially reduces the space between the fibers limiting dialysate flow and dialyzer clearances, particularly at lower dialysate flow rates. 15 To improve dialysate flow within the dialyzer, some manufacturers introduced mechanical spacers between the fibers. As such some dialyzers have increased small solute clearances with dialysate flows above 600 mL/min, 16 whereas others do not achieve greater clearances with higher flows.…”

Is it useful to increase dialysate flow rate to improve the delivered Kt?

“…However, in recent years, new dialysers with hollow fibre undulations, spacer yarns and changes in fibre packing density have been developed in order to improve flow distribution through the dialysate compartment [ 7 - 10 ]. A few publications show that increasing Qd no longer led to an increase in KoA [ 11 ] but these results are based on Kt/V measurement [ 12 , 13 ], (with the limitations explained above), without comparison between dialysers, and without keeping in mind effective time (Te) or effective Qb (Qbe).…”

Three‐Dimensional Simulation of Mass Transfer in Artificial Kidneys

“…Computed tomography (CT) and magnetic resonance imaging (MRI) technologies have been used to detect velocity or concentration profiles in artificial kidneys. Using these two noninvasive technologies, a considerable amount of progress has been made, for example with the visualization of velocity and concentration fields for blood and dialysate , the effect of baffles on the flow uniformity of dialysate , the transport of water or solute across hollow fibers , and the optimization of the flow distribution of dialysate and blood . The limitation of these technologies is that it is difficult to differentiate velocity and concentration profiles on both the blood and dialysate sides in the process of dialysis .…”