Effects of posture on shear rates in human brachial and superficial femoral arteries

Shear rate is significantly lower in the superficial femoral compared with the brachial artery in the supine posture. The relative shear rates in these arteries of subjects in the upright posture (seated and/or standing) are unknown. The purpose of this investigation was to test the hypothesis that upright posture (seated and/or standing) would produce greater shear rates in the superficial femoral compared with the brachial artery. To test this hypothesis, Doppler ultrasound was used to measure mean blood velocity (MBV) and diameter in the brachial and superficial femoral arteries of 21 healthy subjects after being in the supine, seated, and standing postures for 10 min. MBV was significantly higher in the brachial compared with the superficial femoral artery during upright postures. Superficial femoral artery diameter was significantly larger than brachial artery diameter. However, posture had no significant effect on either brachial or superficial femoral artery diameter. The calculated shear rate was significantly greater in the brachial (73 ± 5, 91 ± 11, and 97 ± 13 s−1) compared with the superficial femoral (53 ± 4, 39 ± 77, and 44 ± 5 s−1) artery in the supine, seated, and standing postures, respectively. Contrary to our hypothesis, our current findings indicate that mean shear rate is lower in the superficial femoral compared with the brachial artery in the supine, seated, and standing postures. These findings of lower shear rates in the superficial femoral artery may be one mechanism for the higher propensity for atherosclerosis in the arteries of the leg than of the arm.

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Are the dynamic response characteristics of brachial artery flow-mediated dilation sensitive to the magnitude of increase in shear stimulus?

Journal of Applied Physiology ◽

10.1152/japplphysiol.01190.2007 ◽

2008 ◽

Vol 105 (1) ◽

pp. 282-292 ◽

Cited By ~ 50

Author(s):

K. E. Pyke ◽

J. A. Hartnett ◽

M. E. Tschakovsky

Keyword(s):

Shear Stress ◽

Shear Rate ◽

Dynamic Response ◽

Phase I ◽

Brachial Artery ◽

Flow Mediated Dilation ◽

Final Phase ◽

Stimulus Magnitude ◽

Brachial Artery Diameter ◽

Response Characteristics

The purpose of this study was to determine the dynamic characteristics of brachial artery dilation in response to step increases in shear stress [flow-mediated dilation (FMD)]. Brachial artery diameter (BAD) and mean blood velocity (MBV) (Doppler ultrasound) were obtained in 15 healthy subjects. Step increases in MBV at two shear stimulus magnitudes were investigated: large (L; maximal MBV attainable), and small (S; MBV at 50% of the large step). Increase in shear rate (estimate of shear stress: MBV/BAD) was 76.8 ± 15.6 s−1 for L and 41.4 ± 8.7 s−1 for S. The peak %FMD was 14.5 ± 3.8% for L and 5.7 ± 2.1% for S ( P < 0.001). Both the L (all subjects) and the S step trials (12 of 15 subjects) elicited a biphasic diameter response with a fast initial phase (phase I) followed by a slower final phase. Relative contribution of phase I to total FMD when two phases occurred was not sensitive to shear rate magnitude ( r2 = 0.003, slope P = 0.775). Parameters quantifying the dynamics of the FMD response [time delay (TD), time constant (τ)] were also not sensitive to shear rate magnitude for both phases (phase I: TD r2 = 0.03, slope P = 0.376, τ r2 = 0.04, slope P = 0.261; final phase: TD r2 = 0.07, slope P = 0.169, τ r2 = 0.07, slope P = 0.996). These data support the existence of two distinct mechanisms, or sets of mechanisms, in the human conduit artery FMD response that are proportionally sensitive to shear stimulus magnitude and whose dynamic response is not sensitive to shear stimulus magnitude.

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Observations of rapidly flowing granular-fluid materials

Journal of Fluid Mechanics ◽

10.1017/s0022112085000167 ◽

1985 ◽

Vol 150 ◽

pp. 357-380 ◽

Cited By ~ 251

Author(s):

Daniel M. Hanes ◽

Douglas L. Inman

Keyword(s):

Shear Rate ◽

Granular Material ◽

Volume Concentration ◽

Yield Criterion ◽

Internal Boundary ◽

Similar Data ◽

Shear Rates ◽

Lower Shear ◽

High Shear Rates ◽

Entire Flow

The rapid shearing of a mixture of cohesionless glass spheres and air or water was studied in an annular, parallel-plate shear cell designed after Savage (1978). Two types of flow were observed. In the first type of flow the entire mass of the granular material was mobilized. At high shear rates the shear and normal stresses were found to be quadratically dependent upon the mean shear rate (at constant volume concentration), in general agreement with the observations of Bagnold (1954) and Savage & Sayed (1984), and the ‘kinetic’ theory of Jenkins & Savage (1983). The stresses were found to be weakly dependent on the volume concentration up to approximately 0.5, and strongly dependent above this concentration. For flows in which water was the interstitial fluid, the ratio of the shear stress to the normal stress was slightly higher (than in air), and the stresses at lower shear rates were found to be more nearly linearly related to the shear rate. It is suggested that these effects are contributed to by the viscous dampening of grain motions by the water. The second type of flow was distinguished by the existence of an internal boundary above which the granular material deformed rapidly, but below which the granular material remained rigidly locked in place. The thickness of the shearing layer was measured to be between 5 and 15 grain diameters. The stress ratio at the bottom of the shearing layer was found to be nearly constant, suggesting the internal boundary is a consequence of the immersed weight of the shearing grains, and may be described by a Coulomb yield criterion. A scaled concentration is proposed to compare similar data obtained using different-sized materials or different apparatus. An intercomparison of the two types of flow studied, along with a comparison between the present experiments and those of Bagnold (1954) and Savage & Sayed (1984), suggests that the nature of the boundaries can have a significant effect upon the dynamics of the entire flow.

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Increased brachial artery retrograde shear rate at exercise onset is abolished during prolonged cycling: role of thermoregulatory vasodilation

Journal of Applied Physiology ◽

10.1152/japplphysiol.00936.2010 ◽

2011 ◽

Vol 110 (2) ◽

pp. 389-397 ◽

Cited By ~ 60

Author(s):

Grant H. Simmons ◽

Jaume Padilla ◽

Colin N. Young ◽

Brett J. Wong ◽

James A. Lang ◽

...

Keyword(s):

Shear Rate ◽

Brachial Artery ◽

Prolonged Exercise ◽

Vascular Conductance ◽

Brachial Artery Diameter ◽

Cutaneous Vasodilation ◽

Leg Cycling ◽

Baseline Values ◽

Retrograde Shear

Acute leg exercise increases brachial artery retrograde shear rate (SR), while chronic exercise improves vasomotor function. These combined observations are perplexing given the proatherogenic impacts of retrograde shear stress on the vascular endothelium and may be the result of brief protocols used to study acute exercise responses. Therefore, we hypothesized that brachial artery retrograde SR increases initially but subsequently decreases in magnitude during prolonged leg cycling. Additionally, we tested the role of cutaneous vasodilation in the elimination of increased retrograde SR during prolonged exercise. Brachial artery diameter and velocity profiles and forearm skin blood flow and temperature were measured at rest and during 50 min of steady-state, semirecumbent leg cycling (120 W) in 14 males. Exercise decreased forearm vascular conductance (FVC) and increased retrograde SR at 5 min (both P < 0.05), but subsequently forearm and cutaneous vascular conductance (CVC) rose while retrograde SR returned toward baseline values. The elimination of increased retrograde SR was related to the increase in FVC ( r2= 0.58; P < 0.05) and CVC ( r2= 0.32; P < 0.05). Moreover, when the forearm was cooled via a water-perfused suit between minutes 30 and 40 to blunt cutaneous vasodilation attending exercise, FVC was reduced and the magnitude of retrograde SR was increased from −49.7 ± 13.6 to −78.4 ± 16.5 s−1( P < 0.05). Importantly, these responses resolved with removal of cooling during the final 10 min of exercise (retrograde SR: −46.9 ± 12.5 s−1). We conclude that increased brachial artery retrograde SR at the onset of leg cycling subsequently returns toward baseline values due in part to thermoregulatory cutaneous vasodilation during prolonged exercise.

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Impact of retrograde shear rate on brachial and superficial femoral artery flow-mediated dilation in older subjects

Atherosclerosis ◽

10.1016/j.atherosclerosis.2015.04.017 ◽

2015 ◽

Vol 241 (1) ◽

pp. 199-204 ◽

Cited By ~ 18

Author(s):

Tim H.A. Schreuder ◽

Daniel J. Green ◽

Maria T.E. Hopman ◽

Dick H.J. Thijssen

Keyword(s):

Shear Rate ◽

Femoral Artery ◽

Superficial Femoral Artery ◽

Flow Mediated Dilation ◽

Older Subjects ◽

Artery Flow ◽

Retrograde Shear

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Preserved flow-mediated dilation in the inactive legs of spinal cord-injured individuals

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00958.2003 ◽

2004 ◽

Vol 287 (1) ◽

pp. H374-H380 ◽

Cited By ~ 84

Author(s):

Patricia C. E. de Groot ◽

Fleur Poelkens ◽

Miriam Kooijman ◽

Maria T. E. Hopman

Keyword(s):

Spinal Cord ◽

Shear Rate ◽

Endothelial Function ◽

Femoral Artery ◽

Brachial Artery ◽

Rate Ratio ◽

Arterial Occlusion ◽

Flow Mediated Dilation ◽

Dilatory Response ◽

Spinal Cord Injured

The aim of the study was to assess endothelial function, measured by flow-mediated dilation (FMD), in an inactive extremity (leg) and chronically active extremity (arm) within one subject. Eleven male spinal cord-injured (SCI) individuals and eleven male controls (C) were included. Echo Doppler measurements were performed to measure FMD responses after 10 and 5 min of arterial occlusion of the leg (superficial femoral artery, SFA) and the arm (brachial artery, BA), respectively. A nitroglycerine spray was administered to determine the endothelium independent vasodilatation in the SFA. In the SFA, relative changes in FMD were significantly enhanced in SCI compared with C (SCI: 14.1 ± 1.3%; C: 9.2 ± 2.3%), whereas no differences were found in the BA (SCI: 12.5 ± 2.9%; C: 14.2 ± 3.3%). Because the FMD response is directly proportional to the magnitude of the stimulus, the FMD response was also expressed relative to the shear rate. No differences between the groups were found for the FMD-to-shear rate ratio in the SFA (SCI:0.061 ± 0.023%/s−1; C: 0.049 ± 0.024%/s−1), whereas the FMD-to-shear rate ratio was significantly decreased in the BA of SCI individuals (SCI: 0.037 ± 0.01%/s−1; C: 0.061 ± 0.027%/s−1). The relative dilatory response to nitroglycerine did not differ between the groups. (SCI: 15.6 ± 2.0%; C: 13.4 ± 2.3%). In conclusion, our results indicate that SCI individuals have a preserved endothelial function in the inactive legs and possibly an attenuated endothelial function in the active arms compared with controls.

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TCT-534 To cover or not to cover deep femoral arteries in stenting for bifurcation lesions of superficial femoral artery

Journal of the American College of Cardiology ◽

10.1016/j.jacc.2013.08.1280 ◽

2013 ◽

Vol 62 (18) ◽

pp. B161-B162

Author(s):

Sung-Jin Hong ◽

Young-Guk Ko ◽

Jung-Sun Kim ◽

Myeong-Ki Hong ◽

Yang soo Jang ◽

...

Keyword(s):

Femoral Artery ◽

Superficial Femoral Artery ◽

Femoral Arteries ◽

Bifurcation Lesions

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Low flow-mediated constriction occurs in the radial but not the brachial artery in healthy pregnant and nonpregnant women

Journal of Applied Physiology ◽

10.1152/japplphysiol.00815.2009 ◽

2010 ◽

Vol 108 (5) ◽

pp. 1097-1105 ◽

Cited By ~ 27

Author(s):

Tracey L. Weissgerber ◽

Gregory A. L. Davies ◽

Michael E. Tschakovsky

Keyword(s):

Shear Rate ◽

Pregnant Women ◽

Radial Artery ◽

Brachial Artery ◽

Vascular Function ◽

Low Flow ◽

Flow Mediated Dilation ◽

Brachial Artery Diameter ◽

Function Test ◽

Positive Correlations

Radial artery diameter decreases when a wrist cuff is inflated to stop blood flow to distal tissue. This phenomenon, referred to as low flow-mediated vasoconstriction (L-FMC), was proposed as a vascular function test. Recommendations that L-FMC be measured concurrently with flow-mediated dilation (FMD) were based on radial artery data. However, cardiovascular disease prediction studies traditionally measure brachial artery FMD. Therefore, studies should determine whether L-FMC occurs in the brachial artery. The hypothesis that reduced shear causes L-FMC has not been tested. Brachial and radial artery L-FMC and FMD were assessed in active nonpregnant ( n = 17), inactive nonpregnant ( n = 10), active pregnant ( n = 15, 34.1 ± 1.2 wk gestation), and inactive pregnant ( n = 8, 34.2 ± 2.2 wk gestation) women. Radial artery diameter decreased significantly during occlusion in all groups (nonpregnant, −4.4 ± 4.2%; pregnant, −6.4 ± 3.2%). Brachial artery diameter did not change in active and inactive nonpregnant, and inactive pregnant women; however, the small decrease in active pregnant women was significant. Occlusion decreased shear rate in both arteries, yet L-FMC only occurred in the radial artery. Radial artery L-FMC was not correlated with the reduction in shear rate. L-FMC occurs in the radial but not the brachial artery and is not related to changes in shear rate. Positive correlations between L-FMC (negative values) and FMD (positive values) suggest that radial artery FMD may be reduced among women who experience greater L-FMC. Studies should clarify the underlying stimulus and mechanisms regulating L-FMC, and test the hypothesis that endothelial dysfunction is manifested as enhanced brachial artery L-FMC, but attenuated radial artery L-FMC.

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Relationship between upper and lower limb conduit artery vasodilator function in humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.00290.2011 ◽

2011 ◽

Vol 111 (1) ◽

pp. 244-250 ◽

Cited By ~ 42

Author(s):

Dick H. J. Thijssen ◽

Nicola Rowley ◽

Jaume Padilla ◽

Grant H. Simmons ◽

M. Harold Laughlin ◽

...

Keyword(s):

Endothelial Function ◽

Femoral Artery ◽

Brachial Artery ◽

Superficial Femoral Artery ◽

Popliteal Artery ◽

Lower Limb ◽

Strong Predictor ◽

Lower Limbs ◽

Conduit Artery ◽

Healthy Humans

Brachial artery flow-mediated dilation (FMD) is a strong predictor of future cardiovascular disease and is believed to represent a “barometer” of systemic endothelial health. Although a recent study [Padilla et al. Exp Biol Med (Maywood) 235: 1287–1291, 2010] in pigs confirmed a strong correlation between brachial and femoral artery endothelial function, it is unclear to what extent brachial artery FMD represents a systemic index of endothelial function in humans. We conducted a retrospective analysis of data from our laboratory to evaluate relationships between the upper (i.e., brachial artery) vs. lower limb (superficial femoral n = 75; popliteal artery n = 32) endothelium-dependent FMD and endothelium-independent glyceryl trinitrate (GTN)-mediated dilation in young, healthy individuals. We also examined the relationship between FMD assessed in both brachial arteries ( n = 42). There was no correlation between brachial and superficial femoral artery FMD ( r2 = 0.008; P = 0.46) or between brachial and popliteal artery FMD ( r2 = 0.003; P = 0.78). However, a correlation was observed in FMD between both brachial arteries ( r2 = 0.34; P < 0.001). Brachial and superficial femoral artery GTN were modestly correlated ( r2 = 0.13; P = 0.007), but brachial and popliteal artery GTN responses were not ( r2 = 0.08; P = 0.11). Collectively, these data indicate that conduit artery vasodilator function in the upper limbs (of healthy humans) is not predictive of that in the lower limbs, whereas measurement of FMD in one arm appears to be predictive of FMD in the other. These data do not support the hypothesis that brachial artery FMD in healthy humans represents a systemic index of endothelial function.

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SHEARING EFFECTS ON THE ELECTRORHEOLOGICAL RESPONSE

International Journal of Modern Physics B ◽

10.1142/s0217979201005453 ◽

2001 ◽

Vol 15 (06n07) ◽

pp. 930-937 ◽

Cited By ~ 6

Author(s):

K. TANAKA ◽

S. HASHIMOTO ◽

T. TAKENOUCHI ◽

I. SUGIMOTO ◽

A. KUBONO ◽

...

Keyword(s):

Shear Rate ◽

Electric Field ◽

Transient Response ◽

Stress Responses ◽

Experimental Conditions ◽

Transient Stress ◽

Shear Rates ◽

Lower Shear ◽

Mason Number ◽

The Individual

The steady and transient stress responses were investigated from lower shear rates to higher shear rates at a given strength of the electric field, and the individual experimental conditions were reduced to Mason number ( M n). The electro-rheological response was found in the region with higher M n of the order of 10, and the transient response became faster as the shear rate increased. These results show that the effect of chance of collision among the polarized particles would play an important role even in the region.

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