Reliability of Vasodilation in Response to Passive Leg Movement in Young, Healthy Women

Abstract

Passive leg movement (PLM) elicits rapid vasodilation in the microvasculature that is primarily dependent on nitric oxide. PLM‐induced vasodilation (PLM‐D) therefore, provides an index of lower‐limb microvascular endothelial function. PLM‐D is lower in advanced aging and clinical populations vs. young and healthy controls, demonstrating that PLM‐D provides a useful assessment of vascular responses. However, there is currently limited information regarding the reliability of PLM‐D and no information on the reliability of PLM‐D in women. Therefore, the purpose of this study was to test the hypothesis that PLM‐D in women is reliable when measured over two separate days. Seventeen, young healthy women (22 ± 3 yrs) participated in two identical experimental visits during the early follicular (low‐estrogen) phase of the menstrual cycle. Each visit included three standardized trials of PLM involving one minute of baseline, two minutes of PLM and two minutes of recovery. During the two minutes of PLM an experimenter moved the participant's leg from 90° flexion to 180° extension and back at a set pace of 1 cycle/s. Using duplex ultrasound PLM‐D was characterized by six commonly utilized factors; peak leg blood flow (LBF) and vascular conductance (LVC), peak change above baseline (Δpeak) for LBF and LVC, and area under the curve above baseline (ΔAUC) during the first 60s of PLM for LBF and LVC. The day‐to‐day reliability of PLM‐D was quantified by calculating the Pearson correlation coefficient (r value), intraclass correlation coefficient (ICC) and coefficient of variation (CV). The results demonstrated good day‐to‐day reliability of PLM‐D characterized as peak LBF (r = 0.84, p < 0.001; ICC = 0.84; CV = 13.2%), peak LVC (r = 0.82, p < 0.001; ICC = 0.79; CV = 14.4%), Δpeak LBF (r = 0.83, p < 0.001; ICC = 0.82; CV = 17.8%) and Δpeak LVC (r = 0.83, p < 0.001; ICC = 0.80; CV = 16.5%). Characterization of PLM as ΔAUC demonstrated moderate day‐to‐day reliability; ΔAUC LBF (r = 0.71, p< 0.05; ICC = 0.70; CV = 31.2%) and ΔAUC LVC (r = 0.78, p < 0.001; ICC = 0.74; CV = 27.1%). In conclusion, this study demonstrates that PLM‐D has good day‐to‐day reliability, however, characterization of PLM‐D as peak and Δpeak LBF and LVC is more reliable than ΔAUC. These findings support the use of PLM‐D in future studies as a reliable method to assess lower‐limb microvascular endothelial function in women.

Reliability of the passive leg movement assessment of vascular function in men

“…The current results demonstrate that measurements of PLM‐induced LBF peak, ΔLBF peak , and LBF AUC all exhibit moderate‐to‐high reliability, whether performed repeatedly on the same day or on separate days. These results are in agreement with recently published data in women (Lew et al., 2021). Furthermore, when comparing the reliability of PLM to that reported for the currently most accepted vascular function measurement, FMD, the PLM assessment appears to be at least as reliable.…”

“…The current investigation, in tandem with the data published by Lew and colleagues (Lew et al., 2021), provide important information regarding the reliability of PLM in young, healthy men and women. However, for the PLM assessment to be adopted as a clinical assay of vascular function, reliability will need to be determined across a broad range of populations, including middle‐aged and older adults as well as in those with pathologies.…”

“…Dozens of research articles have been published in the last 10 years utilizing the PLM assessment of vascular function, with very little information regarding the reliability of the assessment method. To date, only one study has been published using a spectrum of statistics in order to elucidate the reliability of PLM‐induced hyperemia (Lew et al., 2021). While this study provided much needed information regarding reliability of PLM in women, it is important to point out that data regarding men is lacking.…”

“…Pearson's correlation coefficient (r), while not a true measure of reliability, were included in order to compare the current results to the recently published study, in women, by Lew et al. (2021). The CV were calculated to represent intrasubject variation between the three measurements performed each within‐day and between‐day.…”

“…(2017), after which no supporting data were published until the recent study by Lew et al. (2021) in a group of seventeen young women. Therefore, there has yet to be a complete report of the reliability of PLM in men.…”