Impact of acute exposure to increased hydrostatic pressure and reduced shear rate on conduit artery endothelial function: a limb-specific response

Abstract

Unlike quadrupeds, humans exhibit a larger hydrostatic pressure in the lower limbs compared with the upper limbs during a major part of the day. It is plausible that repeated episodes of elevated pressure in the legs may negatively impact the endothelium, hence contributing to the greater predisposition of atherosclerosis in the legs. We tested the hypothesis that an acute exposure to increased hydrostatic pressure would induce conduit artery endothelial dysfunction. In protocol 1, to mimic the hemodynamic environment of the leg, we subjected the brachial artery to a hydrostatic pressure gradient ( approximately 15 mmHg) by vertically hanging the arm for 3 h. Brachial artery flow-mediated dilation (FMD) was assessed in both arms before and following the intervention. In protocol 2, we directly evaluated popliteal artery FMD before and after a 3-h upright sitting (pressure gradient approximately 48 mmHg) and control (supine position) intervention. Our arm-hanging model effectively resembled the hemodynamic milieu (high pressure and low shear rate) present in the lower limbs during the seated position. Endothelium-dependent vasodilation at the brachial artery was attenuated following arm hanging (P < 0.05); however, contrary to our hypothesis, upright sitting did not have an impact on popliteal artery endothelial function (P > 0.05). These data suggest an intriguing vascular-specific response to increased hydrostatic pressure and reduced shear rate. Further efforts are needed to determine if this apparent protection of the leg vasculature against an acute hydrostatic challenge is attributable to posture-induced chronic adaptations.

Lymphedema beyond breast cancer

“…The higher incidence of lower extremity lymphedema after inguinofemoral lymph node dissection may be because of anatomic variation, with fewer associated lymphatic collateral pathways, or be related to a specific response to increased hydrostatic pressure in the disrupted lower extremity lymphatics. 55 These findings are concordant with the primary risk factors for lymphedema identified in breast cancer survivors. Specifically, the surgical treatment for breast cancer, which often includes axillary lymph node dissection and/ or mastectomy, is considered a major risk factor for lymphedema 7,56 The extent of lymph node dissection and tumor burden has also been shown to increase the risk of lymphedema.…”

Comparative study of the upper and lower limb skin blood flow control mechanisms in patients with essential hypertension

“…Our findings confirming this suggestion are also supported by the studies investigating increased blood pressure on conduit artery function. In a study, Padilla et al (17) have shown that the brachial artery endothelial vasodilatation was impaired following increase in blood pressure but poplietal artery endothelial function was unaltered. Similar result is found in a study that used the leg press exercise to increase the blood pressure (32).…”

“…The structural and functional alterations of conduit arteries are particularly important in the lower extremities of subjects with cardiovascular disease (15,16). The attenuated endothelium dependent vasodilatation has been found in the upper extremities of subject during acute rise in blood pressure induced by hydrostatic factor (17). Despite the significant work performed on the primary conduit vessels of the arm and leg to assess limb vascular heterogeneity (10)(11)(12)(13)17), only one single work (7) compared upper and lower limb cutaneous vascular function in humans.…”

“…The attenuated endothelium dependent vasodilatation has been found in the upper extremities of subject during acute rise in blood pressure induced by hydrostatic factor (17). Despite the significant work performed on the primary conduit vessels of the arm and leg to assess limb vascular heterogeneity (10)(11)(12)(13)17), only one single work (7) compared upper and lower limb cutaneous vascular function in humans. And, there are currently no data comparing cutaneous blood flow recorded from upper and lower limbs in EHT patients.…”

Seven Days Breaking Up Prolonged Sitting Improves Systemic Endothelial Function in Sedentary Men

“…There are numerous sitting opportunities throughout the day and the average sitting time for American adults is~8 hr/day [2]. Sitting creates a unique anatomical and physiological milieu in the legs including bends in the femoral and popliteal artery, increased viscosity [3], blood pressure [4] and decrease in arterial shear rates [5]. Interestingly in humans, lower extremities exhibit an increased distribution of atherosclerosis as compared to the upper extremities [6][7][8].…”