Improving Hollow Fiber Dialyzer Efficiency with a Recirculating Dialysate System I: Theory and Applicability

Abstract

The mathematical theory that underlies a novel non-regenerated recirculating dialysate system (RDS) for improving diffusive clearance in hemodialyzers is presented. The theory states the conditions that hemodialyzers must meet to be suitable in RDS optimization. We have verified the applicability of the RDS for several Cuprophan and polysulfone (PS) commercial dialyzers, showing that PS (synthetic) membranes achieve the highest increments of diffusive clearance. A numerical simulation analysis over more general conditions defined by the dimensionless groups of the system demonstrated that the highest diffusive clearance improvements are achieved in dialyzers operating with a low value of the diffusive mass-transfer area/blood flow rate ratio. This study has provided the base for the assessment of the performance of the RDS as compared to several high-efficiency systems, presented in Part II of this work [M. Prado, L. M. Roa, A. Palma, and J. A. Milan, Ann. Biomed. Eng. (2004) submitted].

Improving Hollow Fiber Dialyzer Efficiency with a Recirculating Dialysate System II: Comparison Against Two-Chamber Dialysis Systems

“…The functionsR t (Q d ) for these dialyzers were calculated by linear regression in Prado et al 28 from the experimental measurements of Allen et al 2 and Leypoldt and Cheung. 19 These are presented here for convenience.…”

“…The value of V t is taken approximately equal to the dialyzer dialysate volume with the aim of keeping the time-constant of the tank solute concentration, c t , lesser than the residence time of the dialysate through the dialyzer. 28 This condition guarantees the steady-state condition of the system, which strongly simplifies the analysis.…”

“…28 The efficiencies of the double-chamber systems depend on these four dimensionless parameters also. This fact provides a clear approach to compare the performance of these dialysis systems.…”

“…Its theoretical foundation was presented in Part I (briefly reviewed below). 28 This work addresses the comparison by digital simulation of the RDS against the twochamber systems of Fig. 1.…”

Two‐Dimensional Mass‐Transfer Model of a Flat‐Plate Dialyzer with Ultrafiltration Operation

“…Furthermore, Henderson [31] and Leber et al [32] showed that ultrafiltration operation not only improves the mass transfer efficiency in a hemodialysis process but can also reduce the treatment time and is tolerable by patients. Prado et al [33] designed a non-regenerating, recirculating dialysate system to improve the efficiency of a hollow fiber dialyzer.…”