Reproducibility of ultrasound scan in the assessment of volume flow in the veins of the lower extremities

PURPOSE: The purpose of this study was the identification of the optimal settings of ultrasound scan flow measurement in the veins and the determination of whether the standardization of these settings can provide acceptable reproducibility of the venous flow measurements in individual segments of the lower extremity veins. METHODS: The venous cross-sectional area, the time average mean velocity, and the venous volume flow of 25 healthy volunteers were examined with duplex ultrasound scanning. Reproducibility was examined with different measurement settings. Doppler scan sample volume size, ultrasound scan beam incident angle, and time interval of measurement were varied across a spectrum for arrival at the setting for highest reproducibility of the flow volume measurements. Test-retest reproducibility of venous flow volume measurements then was investigated with optimized settings. RESULTS: The highest repeatability of volume flow measurements was achieved when the full lumen of the vein was insonated (coefficient of repeatability [CR] = 1.88 cm/s), the ultrasound scan beam incident angle was equal to 60 degrees (CR = 1.56 cm/s), and the measurement time was more than 40 seconds (CR = 1.64 cm/s). The mean values of volume flow were 360 mL/min in the common femoral vein, 147 mL/min in the superficial femoral vein, 86 mL/min in the profunda femoral vein, and 38 mL/min in the greater saphenous vein. Test-retest repeatability coefficients were 96.9 mL/min for the common femoral vein, 70.2 mL/min for the superficial femoral vein, 40.8 mL/min for the profunda femoral vein, and 16.8 mL/min for the greater saphenous vein. CONCLUSION: The reproducibility of ultrasound scan measurements of volume flow in veins is optimized with the use of sampling volumes that cover the entire venous lumen, with an incident angle of 60 degrees and measuring for 40-second intervals or longer. With these defined variables, volumetric measurements are sufficiently repeatable. the values of flow volume measured with duplex ultrasound scanning were comparable to those with thermodilution techniques that were reported previously.