Abstract
Blood flow rate through the dialysis circuit is an important factor affecting the dialyzer performance especially for removal of relatively low molecular weight substances. Actual blood flow rate, however, sometimes varies during dialysis treatment due to the condition of the patient's vascular access even though the blood flow rate on the blood pump remains at a constant setting. We developed a new method of measuring the actual blood flow rate through the circuit based on two point hematocrit values (CRIT-2 Point Method). Using two hematocrit monitors, CRIT-LINE (JMS Co. Ltd.), this method estimates the actual blood flow rate based on the difference in hematocrit values between the inlet and outlet of the dialyzer, caused by removal of water from the blood flowing through the dialyzer. In vitro experiments using bovine blood were carried out to evaluate the accuracy of this method. Initially, there was a relative error of the hematocrit value between the CRIT-LINE monitors and a method of correcting the error between monitors was added in order to estimate the actual blood flow rate. The blood flow rate obtained from the CRIT-2 Point Method after error correction (QB-crit) was compared with the actual blood flow rate measured directly using a measuring cylinder (QB-actual). A good correlation between the QB-crit and QB-actual values was obtained, indicating the high accuracy of this method. The percent error of the QB-crit to QB-actual was within±10%. A dialysis machine equipped with the CRIT-2 Point Method to measure the actual blood flow rate will be available in the near future in order to facilitate a safe and adequate dialysis treatment for each patient.
