Abstract
The fluid and solute transfer performances of dialyzers have been improved as a result of advances in membrane and device technology. To date, many types of dialyzers with high performance membranes have been developed. In some of these dialyzers, the pressure drop in the blood and dialysate streams occurs in a countercurrent manner, inducing internal filtration/back filtration (IF/BF). Namely, filtration from the blood through the membrane and to the dialysate occurs in the upstream of the blood flow and back filtration from the dialysate to the blood occurs in the downstream.
Recently, several types of dialyzer with enhanced internal filtration have been introduced for clinical application as a means of improving the efficiency of solute removal, and the enhanced internal filtration in these dialyzers has increased the convective transport of the solute besides the diffusive transport. The internal filtration flow rates (QIF) of the dialyzer, however, have never been evaluated precisely. During our studies, blood flow velocity in a cross-sectional plane of a dialyzer was measured by pulse Doppler ultrasonography to evaluate QIF. An in vitro study using bovine blood was carried out to determine the profile of local blood flow velocity with a probe slider that enables the probe to move in parallel along a dialyzer. The Doppler ultrasonography is a useful method for bedside monitoring of QIF in several dialyzers, because it is noninvasive to the patient and produces reliable data with higher reproducibility.
