Computational Analysis of Flow Regulatory Mechanism in Artificial Kidney

Abstract

There is an enormous need in the health welfare sector to manufacture inexpensive dialyzer membranes with minimum dialysis duration. In order to optimize the dialysis cost and duration, an in-depth analysis of the effect of dialyzer design and process parameters on toxins (ranging from small to large size molecules) clearance rate is required. The efficiency of this transport phenomena depends on the hollow fiber geometry, membrane characteristics and operating variables. It is difficult to translate the in vivo transfer process with in vitro experiments as it involves high cost to produce various designs and membranes for dialyzer. Mathematical analysis and enhanced computational power of computers can translate the transport phenomena occurring inside the dialyzer while minimizing the development cost. In the past 30 years numerous mathematical models have been proposed to mimic the transport phenomena occurring in vivo. The models have been simulated through different software including MATLAB®, ANSYS Fluent® and COMSOL Multiphysics®. In vitro analysis to optimize the membrane characteristics and module geometry have also been performed side by side. However, due to little communication between the in vitro and in silico research there is no efficient tool for the wet lab workers that enables them to rigorously determine the effect of membrane properties and other process parameters on clearance efficiency of dialyzer module. This void hinders to develop a membrane module that efficiently mimics the function of human kidney. To the best of authors’ knowledge, COMSOL Inc. has developed an application that enable to study the effect of few membrane properties and design parameters on module clearance efficiency but it does not mimic the transport phenomena associated with dialyzers merely because of the simplicity of the mathematical model. Nevertheless, it inspires towards the development of a better application that could reduce the cost of R&D needed to optimize membrane properties and module design. In first part of this study, a steady-state microscopic balance was developed to mimic the convective and diffusive transport of low molecular weight (LMW) solutes i.e. urea and glucose and middle molecular weight (MMW) solutes i.e. endothelin and β2-Microglobulin inside the dialyzer. The aim of computational analysis performed with these model equations is to figure out those factors that play vital role in enhancing the dialyzer clearance. Tortuous Pore Diffusion Model (TPDM) was used to mimic the transport of solute inside the porous medium and convection-diffusion equations were used to establish the mass transfer in blood and dialysate compartment. In the second part, development of a user-friendly stand-alone application is described thoroughly. Keywords: artificial kidney; hemodialysis; membrane; hollow fiber dialyzer, CFD