Reliable fluid‐mechanical characterization of haemofilters: Addressing the deficiencies of current standards and practices

다국어 초록 (Multilingual Abstract)

Facile methods for accurate fluid‐mechanical characterization of haemofilters (HF) are indispensable for haemofiltration process improvements, equipment design/optimization, and reliable module specifications. Currently employed methods, implemented through specific experimental in vitro protocols, are assessed herein in detail, considering the conditions prevailing during haemofiltration. Minimum number of key parameters required to fully describe the common countercurrent flow field, in the HF active section, include membrane permeance K and friction coefficients in lumen and shell side (ff and fs). It is shown that the countercurrent flow mode itself is incapable of yielding these parameters, based on externally measured flow rates and pressures. Similarly, the relevant ISO protocol is deficient as it can only provide rough underpredictions of permeance K. The causes of such inherent deficiencies of current standards and practices are analyzed. In contrast, a recently developed methodology, accounting for the (heretofore ignored) pressure drop in module headers and combining a mechanistic theoretical model with experimental data from 2 special haemofilter operating modes, yields an accurate determination of the key parameters (K, ff, fs). Additionally, it permits a full description of flow field for Newtonian liquids, for both constant and axially varying viscosity in fiber‐lumen due to the transmembrane flux. Development of new reliable standards is suggested, facilitated by the insights gained in this work.



Haemofilters comprise two headers and the active section, where toxicants are removed from blood (through hollow‐fiber membranes) to counter‐currently flowing dialysate.

Complete fluid‐mechanical characterization necessitates determination of module/membrane‐ permeance K and friction‐coefficients ff and fs due to flows in fiber‐lumen and shell‐side; additionally, pressure drop in the headers should be accounted for.

The deficiencies are analyzed of current ISO‐standards and practices that do not permit such complete and reliable characterization, which is possible by a recently developed method.