Reliability of popliteal artery flow‐mediated dilation in the seated position

Flow-mediated dilation (FMD), a noninvasive measure of endothelial function, is commonly measured in the popliteal artery in the supine and upright body positions. However, reliability studies of the measurement in these positions are not well studied. This study aimed to examine the trial-retrial and visit-to-visit reliability of popliteal artery FMD in the seated position. Popliteal artery FMD was measured in 20 healthy adults across two visits in the seated and prone positions to assess visit-to-visit reliability. Two measurements were taken for each body position at each visit to assess trial-retrial reliability. %FMD was calculated as the percent change from baseline diameter to peak diameter. The reliability of FMD was assessed via the intraclass correlation coefficient (ICC). Popliteal artery %FMD shows moderate-to-good reliability in the seated position (ICC: 0.67-0.89) and poor-to-moderate reliability in the prone position (ICC: 0.25-0.74) within and between visits. There were no significant differences in baseline diameter or minimum diameter between body positions, visits, or trials (p > 0.05). %FMD and peak diameter following cuff deflation demonstrated no significant difference between body positions (p > 0.05). Popliteal artery FMD demonstrates good reliability in the seated position, supporting the development of a standardized measurement protocol.