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Abstract: SA-PO618

Blood Flowrate Accuracy with Diality Hemodialysis System

Session Information

Category: Dialysis

  • 801 Dialysis: Hemodialysis and Frequent Dialysis


  • Poppe, Clayton, Diality, Irvine, California, United States
  • Hyun, Nicholas, Diality, Irvine, California, United States
  • Murakami, Blaine, Diality, Irvine, California, United States

As laid out by Williams, Jensen, Gillum and Nabut,[1] blood flow accuracy in hemodialysis machines often does not match the manufacturers’ stated accuracy at high blood flowrates. Flowrates might be lower by as much as 80-100 ml/min at a setpoint of 500 ml/min. This compares to the stated accuracy of +/-10% by most hemodialysis machine manufacturers. This difference in blood flowrate can lead to a reduction in Kt/V of 8.4%, depending on the dialysate flowrate. The Diality Hemodialysis System corrects for the factors responsible for reducing the expected flowrate leading to more accurate control of the blood flowrate and thus a higher Kt/V that better matches the theoretical value for dose delivered.

[1] Williams HF, Jensen K, Gillum D, Nabut J. Blood pump speed vs. actual or "compensated" blood flow rate. Nephrol Nurs J. 2007 Sep-Oct;34(5):491-9, 525. PMID: 18041451.


The challenge in controlling blood flow is that parameters that are appropriate for high blood flows may not work a low flowrates. An algorithm that predicts the flowrate from independent variables is used to control the blood flow using a Proportional-Integral-Differential (PID) control methodology. The factors feeding into this algorithm are independently correlated with changes in blood flow. These include:

- Pump head speed
- Inlet and Outlet Pressures
- Tubing Aging
- Temperature


The graph on the left-hand side of Figure 1 shows the accuracy of blood flow control at 100 ml/min while the graph on the right-hand side shows the accuracy of blood flow control at 500 ml/min. The green line represents the measured flow from a reference flowmeter while the orange line represents the algorithmically calculated flow from the device. Actual flowrates are well within the stated accuracy of +/-10% for both low and high flowrates.


Understanding the variables that lead to changes in blood flow and using them to control blood flow in real time can leads to better blood flow accuracy. This in turn can lead to higher average Kt/V for higher treatments with high blood flowrates.

Figure 1: Blood Flowrates of 100 ml/min (right) and 500 ml/min (left)