Intra- and Inter-rater Reliability of Sonographic Blood Flow Measurements

The recommendation to use relative cuff pressures during blood flow restriction (BFR) training is based on a few studies that have measured arterial blood flow across a range of cuff pressures. These studies have not reported the reliability of measuring blood flow using ultrasound. PURPOSE: This study evaluated the inter- and intra-rater reliability of sonographic measures of blood flow of the radial and superficial femoral arteries. METHODS: Two experienced sonographers used Doppler ultrasound to capture videos of the radial and superficial femoral arteries in 15 participants on the same day. One sonographer captured a second set of videos. The videos were stored for later analysis by the two sonographers. Paired t-tests and 2-way random or mixed effects, absolute agreement intraclass correlations (ICC) were used to measure the reliability of (1) one sonographer analyzing his/her own set of videos two times, (2) one sonographer analyzing two of his/her videos of the subjects, (3) two sonographers analyzing their own videos of the subjects, and (4) two sonographers analyzing the same set of videos. RESULTS: All ICC values exceeded 0.98 indicating high intra- and inter-reliability of measuring blood flow from ultrasound videos of the small radial artery and larger superficial femoral artery. The paired t-tests also indicated highly reliable measures of blood flow. The few comparisons that were statistically significant were small and of little practical significance. Only 13 (11%) of the 120 blood flow comparisons of the radial artery had differences >10 mL/min. All of the 120 blood flow comparisons of the superficial femoral artery were within 10 mL/min. CONCLUSIONS: Well trained and experienced sonographers can reliably measure blood flow from one or multiple videos captured by themselves or another sonographer. We recommend well designed training efforts and evaluation of competencies for those involved in measuring blood flow as part of BFR training.