Background: We sought to determine the effects of unilateral lower-limb external pneumatic compression (EPC) on bilateral lower-limb vascular reactivity and skin blood flow.
Methods: Thirty-two participants completed this two-aim study. In AIM1 (n = 18, age: 25.5 ± 4.7 years; BMI: 25.6 ± 3.5 kg/m2), bilateral femoral artery blood flow and reactivity (flow mediated dilation [FMD]) measurements were performed via ultrasonography at baseline (PRE) and immediately following 30-min of unilateral EPC treatment (POST). AIM2 (n = 14, age: 25.9 ± 4.5; BMI: 27.2 ± 2.7 kg/m2) involved 30-min unilateral EPC (n = 7) or sham (n = 7) treatment with thermographic bilateral lower-limb mean skin temperature (MST) measurements at baseline, 15-min of treatment (T15) and 0, 30 and 60-min (R0, R30, R60) following treatment.
Results: Comparative data herein are presented as mean ± 95% confidence interval. AIM1: No significant effects on total reactive hyperemia blood flow were observed for the treated (i.e., compressed) or untreated (i.e., non-compressed) leg. A significant effect of time, but no time*leg interaction, was observed for relative FMD indicating higher reactivity bilaterally with unilateral EPC treatment (FMD: +0.41 ± 0.09% across both legs; p < 0.05). AIM2: Unilateral EPC treatment was associated with significant increases in whole-leg MST from baseline during (T15: +0.63 ± 0.56 °C in the visible untreated/contralateral leg, p < 0.025) and immediately following treatment (i.e., R0) in both treated (+1.53 ± 0.59 °C) and untreated (+0.60 ± 0.45 °C) legs (p < 0.0125). Across both legs, MST remained elevated with EPC at 30-min post-treatment (+0.60 ± 0.45 °C; p < 0.0167) but not at 60-min post (+0.27 ± 0.46 °C; p = 0.165). Sham treatment was associated with a significant increase in the treated leg immediately post-treatment (+1.12 ± 0.31 °C; p < 0.0167), but not in the untreated leg (-0.27 ± 0.12 °C). MST in neither the treated or untreated leg were increased relative to baseline at R30 or R60 (p > 0.05). Finally, during treatment and at all post-treatment time points (i.e., R0, R30 and R60), independent of treatment group (EPC vs. sham), there was a significant effect of region. The maximum increase in MST was observed at the R0 time point and was significantly (p < 0.05) larger in the thigh region (+1.02 ± 0.31 °C) than the lower-leg (+0.47 ± 0.29 °C) region. However, similar rates of MST decline from R0 in the thigh and lower leg regions were observed at the R30 and R60 time points.
Discussion: Unilateral EPC may be an effective intervention for increasing skin blood flow and/or peripheral conduit vascular reactivity in the contralateral limb. While EPC was effective in increasing whole-leg MST bilaterally, there appeared to be a more robust response in the thigh compared to the lower-leg. Thus, proximity along the leg may be an important consideration in prospective treatment strategies.
Keywords: External pneumatic compression; Flow mediated dilation; Mean skin temperature; Skin blood flow; Thermography; Vascular reactivity.