To begin, place the probe on the inguinal region of the participant then find the optimal arterial section for leg blood flow or LBF measurements. Make a cross-sectional image of the common femoral artery. Turn the Gain button clockwise to increase gain and counterclockwise to decrease gain.
Turn the Depth button clockwise to increase the depth and counterclockwise to decrease it. After adjustment, ensure that the artery is in the middle of the screen and the blood is black. In 2D mode, press Freeze once then scroll using the track ball to find an end-systolic image.
Press Measure once and move the cursor to the superficial intimal layer of the artery then press Enter. Next, move the cursor to the deep intimal layer of the artery and press Enter to obtain the diameter at end-systole. Press Freeze then turn the probe 90 degrees clockwise while keeping the artery centered on the screen and probe parallel to the artery to create a longitudinal view.
Press the PW button, followed by the Measure button. Move the cursor to auto and press Enter then click Flow Volume and press Enter. Move the cursor to Live and press Enter to obtain the trace and finish by pressing Measure once.
To obtain the velocity at an insonation angle of less than 60 degrees. Turn the Steer Angle button clockwise to decrease it and counterclockwise to increase it. Turn the Angle Correction button to validate the trace captured with the cursor horizontal to the artery.
Press Sample Volume to adjust the volume according to the width of the artery while avoiding contact with the artery wall. To decrease the sample size, press the left arrow and increase by pressing the right arrow. Next, turn the Sound button clockwise then obtain the blood flow velocity trace with simultaneous 2D visualization of the artery and audiovisual blood velocity feedback.
Obtain the first trace during seated rest for 30 seconds, and press Image Store twice to save the trace. Then, instruct the participant to maintain a pace of 60 RPM during the test. Using the same conditions, record the trace data at a pace of 60 RPM and zero watts.
Add resistance to the single leg knee extensor chair. Then, ask the participant to complete a minimum of 150 seconds of exercise before obtaining 30 seconds of trace. Press Image Store twice to save the trace.
Once all the images are obtained, press Review, press track ball and move the cursor to the desired image then double click on Enter. Once the desired trace appears, press Measure. Then, from the dropdown menu, select Flow Volume and press Enter.
Next, select 2D Ultrasound Image and press Enter. Then drag the cursor until it reaches the diameter measured during rest and press Enter again. Turn the Cursor Select button clockwise twice.
Then, by scrolling the track ball and pressing Enter, choose a 30-second trace between two vertical lines. There were no statistically significant differences in the absolute LBF values between the Within Day or Between Day measurements. LBF increased progressively across the incremental workloads.
The value ranges from 0.36 liter per minute at rest to 2.44 liter per minute during exercise at 18 watts. Bland Altman Plots of LBF measurements for Within Day reliability showed no outliers. In contrast, a few outliers were observed in the Between Day measurements, and several outliers were observed during the Interrater measurements.
In test/retest reliability, the smallest real difference values were lower for Within Day measurements compared to the Between Day and Interrater measurements. Similarly, the coefficient of variation values were higher in the Between Day and Interrater measurements compared to the Within Day measurements. The intraclass correlation coefficient values showed that the reliability at all workloads during Within Day and Between Day were higher than 0.90.
Conversely, the Interrater measurements yielded ICC values as low as 0.41.
