Effects of vertical tubing on the flow status of a blood inlet port

To evaluate the influence of the flow conditions of blood entering a dialyzer port on the occurrence of blood clotting within the dialyzer, we examined blood flow through the dialyzer port when conducted to the port through arterial line tubing maintained in a vertical position immediately above the port by a special holder. Five dialyzer models: TF-1500H (TF), PS-1.6UW (PS), BK-1.6UW (BK), CL-SU15N (CL), and PAN-13DX (PAN), whose blood ports differ in shape, were tested. With the arterial line tubing held vertically over lengths of 0mm, 50mm, 100mm, and 150mm immediately above the blood inlet port and electrodes placed in the port, simulated blood was circulated through the test circuit, and differences in flow conditions between different points inside the port were determined from voltages measured 30 seconds and 7 minutes after the start of circulation. This procedure was carried out ten times for each dialyzer tested and each length of vertical tubing. Except for the CL dialyzer, there was a positive correlation between the length of the vertical segment of the arterial tubing and the averaged sum of voltage differences after 30 seconds of circulations. The correlations between the length of the vertical [segment of] tubing and the both the standard deviation of the averaged sum of voltage differences and the maximum voltage minus the minimum voltage measured at each point were negative. These results indicate that as the length of the vertical [segment of] tubing was increased, flow inside the port become more centralized. As a result, the difference in flow rate between the central and peripheral areas increased, and the difference between points within the peripheral area decreased. We also found in clinical tests that the use of the special holder to keep the tubing immediately above the blood inlet port vertical helped to reduce blood clotting in the port and fibers. This suggests that providing a vertical path of adequate length immediately above the dialyzer port is important to reducing blood clotting in different types of dialyzers.