Theoretical evaluation of the performance characteristics of a combined hemodialysis/hemoperfusion system — I. Single pass flow

Abstract

A mass transfer model with single pass flow is proposed for evaluating the performance characteristics of a combined system composed of a dialyzer for hemodialysis (HD) and a coated adsorbent packed cartridge for hemoperfusion (HP). In the dialyzer, the mass transfer equation is represented in terms of three dimensionless parameters, i.e., extraction ratio, number of transfer unit, and ratio of flow rates. For the hemoperfusion cartridge, the model equations are derived by formulating the following four processes: convective mass transfer in the bed, fluid phase mass transfer around a coated adsorbent particle, transport across a film of coated membrane, and diffusion within an adsorbent particle. The Freundlich isotherm model is used for the adsorption on adsorbent particles. Applications of the mathematical model to systems to be potentially used in clinical practice are discussed. Solutions for two different sequences of arrangement, i.e., HD‐HP and HP‐HD, are obtained and discussed in terms of their performance efficacies. Theoretical results demonstrate that the HD‐HP arrangement will give better performance in most clinical encounters.