Reliability of Popliteal Artery Flow-Mediated Dilation in the Seated and Prone Positions

Introduction: Flow-mediated dilation (FMD) is a noninvasive measurement of endothelial function, which is a useful prognostic tool for cardiovascular disease risk. Despite its widespread use since 1992, the reproducibility of FMD varies widely between studies. This variability in reproducibility is especially significant in the case of the popliteal artery due to different methodological approaches. Studies perform popliteal artery FMD in various body positions, with the prone and seated positions being the most common. However, no studies have examined the reproducibility of both the seated and prone positions of the popliteal artery FMD. Therefore, the aim of this study is to examine the test-retest and visit-to-visit reliability of the popliteal artery FMD in the seated position and to determine whether differences in %FMD exist between seated and prone positions. Methods: The popliteal artery FMD was measured on two occasions in 20 healthy young adults, both in seated and prone positions. Popliteal artery diameter was measured at baseline, during 5 minutes of cuff occlusion at 220 mmHg, and following cuff deflation for 5 minutes. FMD was calculated as the percent change from baseline diameter to peak diameter. The reliability of FMD was assessed in the prone and seated positions via intraclass correlation coefficient (ICC). Further, differences in FMD between the prone and seated positions were assessed via the three-way repeated measures analysis of variance (body position x visit x trial). Results: The results demonstrate that the popliteal artery %FMD has moderate to good reliability in the seated position both within and between visits (ICC values range from 0.67 to 0.89), whereas the prone position has poor to moderate reliability within and between visits (ICC values range from 0.25 to 0.74). Also, there were no significant differences in baseline diameter, peak diameter, or minimum diameter between body positions, visits, or trials except for %FMD being higher following the 2nd visit compared to the 1st visit. Conclusion: The popliteal artery FMD has a good reliability when measured in the seated position which can contribute to the development of a standard protocol to measure the FMD in the seated position.