Abstract
The dependence of diffusive clearance of a high performance dialyzer (SSP-1.5L) for vitamin B12 on dialysate flow rate was larger than that of a conventional dialyzer (SSP-1.5H) with the same dimension as SSP-1.5L. Diffusive resistance of highly permeable membranes is no longer the sole factor governing removal rate of dialyzers for middle molecule substances. We determined optimal dimensions of high performance dialyzers, using empirical equations for dialysate- and blood-side mass transfer and the tortuous pore model combined with equations for estimating pressure drop and priming blood volume. The fraction of membrane diffusive resistance of SSP-1.5L for vitamin B12 calculated from the theory was 0.73 times that of SSP-1.5H. The decrease in inner diameter of the membrane highly increased blood-side pressure drop in spite of slight improvement in diffusive clearance for vitamin B12, leading to optimal inner diameter of approximately 200μm. The decrease in inner diameter of the shell also increased diffusive clearance for vitamin B12. However, the fiber density of 75% with decreasing inner diameter of the shell was calculated to be the upper limit that would maximize the solute removal performance. Dimension of SSP-1.5L was nearly equal to the optimal one calculated from the theory.
