Analysis of variable flow Doppler hemodialysis access flow measurements and comparison with ultrasound dilution

The variable flow (VF) Doppler method determines access blood flow from the pump speed-induced change in Doppler signal between the arterial and venou s needles. This study evaluated 35 patients in two analyses to assess VF Do ppler measurement reproducibility (54 paired measurements) and compared VF Doppler and ultrasound dilution flow measurements (24 paired measurements). VF Doppler measurement variations were 4% for access flow less than 800 mL /min (n = 17), 6% for access flow of 801 to 1,600 mL/min (n = 22), and 11% for access flow greater than 1,600 mL/min (n = 15). The mean measurement co efficient of variation was 7% for VF Doppler compared with 5% for ultrasoun d dilution. Correlation coefficients (r) between VF Doppler and ultrasound dilution access flow measurements were 0.79 (n = 24; P < 0.0001), 0.84 for access flow less than 2,000 mL/min (n = 20; P < 0.0001), and 0.91 for acces s flow less than 1,600 mL/min (n = 18, P < 0.0001). VF Doppler measurements using indicated versus measured pump flow rates correlated highly (r = 0.9 9; P < 0.0001). VF Doppler therefore yields reproducible access volume flow measurements that correlate with ultrasound dilution measurements. The VF Doppler method is dependent on the pump-induced change in access Doppler si gnal and therefore is inherently most accurate and reproducible at lower ac cess blood flow rates. This method appears capable of determining access fl ow rates in the clinically useful range. (C) 2001 by the National Kidney Fo undation, Inc.