An adjustable systemic-pulmonary artery (SPA) shunt is being developed that consists of apolytetrafluoroethylene (PTFE) graft with a screw plunger mechanism. This device would allowfull control of flow through SPA shunts used to augment pulmonary blood flow in neonates bornwith single ventricle physiology. The objective of this study is to evaluate the changes this mechanismhas on flow fields for a 4 mm and 5 mm adjustable SPA shunt. Two in vitro models wereexamined; an idealized model with an axisymmetric constriction and a model developed from 3-Dreconstruction of the actual shunt under asymmetric constriction. These models were used to measurethe instantaneous velocity and vorticity fields using Particle Image Velocimetry (PIV) underboth steady and pulsatile flow conditions. Recirculation regions and maximum values of velocity,vorticity, and shear stress are compared between the 4 mm and 5 mm models. The results indicatethat for the idealized model of both shunts, separation regions are much smaller, persistingfor approximately 0-1.75 diameters downstream of the constriction, while for the realistic modelsseparation regions of 2.5 diameters downstream were observed. Additional models of a 4 mm and5 mm shunt were tested under pulsatile conditions matching Re of 1061 and 849 and a Womersleynumber of 4.09 and 5.12, respectively, as seen in vivo. The maximum shear rates observed in bothshunts are within an allowable range without inducing platelet aggregation or hemolysis. However,regions of reverse flow exist distal to the throat, leading to possible concerns of plaque formation.Further in vivo testing will be needed to address this concern. This work is part of an extensiveeffort in developing a completely implantable adjustable systemic-pulmonary artery shunt.

Os ensaios de palheta são frequentemente utilizados na estimativa da resistência não-drenada de depósitos de argilas moles devido à simplicidade do equipamento, rapidez de execução e baixo custo. A velocidade de deformação em ensaios de palheta de campo é, geralmente, de 6º/min. Contudo, os resultados destes ensaios são influenciados por vários fatores e, dentre eles, a velocidade de rotação pode ser considerada um dos mais importantes. Sob condições não-drenadas, os materiais argilosos apresentam ganho de resistência não-drenada com o aumento da velocidade de cisalhamento, resultante da viscosidade da água adsorvida nas partículas de solo. Como o ensaio de palheta tem sido cada vez mais utilizado para estimar a resistência não-drenada de outros solos de granulometria fina, como siltes, resíduos de mineração entre outros, é preciso ter cautela na interpretação dos resultados nestes materiais, pois a utilização da velocidade padrão de campo pode levar à ocorrência de drenagem parcial durante o cisalhamento e, nestes casos, os solos apresentam resistência e rigidez maiores que sob condições não-drenadas. Desta forma, o objetivo deste trabalho consiste na avaliação da influência da velocidade de rotação do ensaio de palheta na resistência dos solos. Foram realizados ensaios de palheta, utilizando palhetas de 20,2, 25,5 e 40,0 mm de diâmetro e com relação altura-diâmetro igual a 2 a velocidades de rotação de 0,68 a 10800o/min, utilizando três misturas compostas por 85% caulim e 15% bentonita com 100, 130% e 160% de umidade (argilosas), uma mistura composta por caulim puro a 50% de umidade (silte) e uma mistura composta por 60% caulim e 40% areia com 40% de umidade (silte). A partir dos resultados dos ensaios de palheta, observou-se que a resistência não-drenada aumenta com a velocidade, sob condições não-drenadas, tanto para os solos argilosos quanto para os siltosos. A resistência não-drenada também é influenciada pelo diâmetro da palheta e pelo índice de vazios do solo, e consequentemente pelo seu teor de umidade. A resposta viscosa dos ensaios de palheta ao longo de toda a faixa não-drenada pode ser descrita por uma equação potencial (para valores de velocidade adimensional maiores que 10). Os solos siltosos, especialmente a argila misturada com areia, também apresentam aumento de resistência com o aumento da velocidade, sob condições não-drenadas, mais pronunciado que para os solos argilosos. Entretanto, a pequenas velocidades, uma parcela do excesso de poro pressão gerado durante a rotação da palheta foi dissipado, ocasionando efeitos de drenagem parcial durante o cisalhamento. O torque medido durante os ensaios é influenciado pelas dimensões da palheta. Porém, não foi verificada qualquer tendência de variação na resistência normalizada (T/Tref) decorrente das dimensões da palheta. A velocidade normalizada (V) considera diretamente, além da velocidade, a geometria da palheta e o coeficiente de adensamento do solo e reflete os efeitos de permeabilidade, rigidez e velocidade de cisalhamento, fatores que também controlam a viscosidade. Desta forma, os efeitos viscosos dos ensaios de palheta são representados com precisão no espaço normalizado. Além da avaliação dos efeitos de velocidade devido a viscosidade, a normalização dos resultados no espaço T/Tref versus V possibilita também a avaliação dos efeitos de drenagem parcial. Ou seja, dois fenômenos físicos distintos podem ser identificados e interpretados utilizando a mesma abordagem. / Vane tests are frequently used to estimate the undrained shear strength of soft clays deposits because of the equipment simplicity, speed and low costs. The strain rate used in vane shear tests is generally of 6o/min. However, vane tests results are influenced by many factors and rate of shear can be considered one of the most important. Under undrained conditions, undrained shear strength of clayey soils increases with shear velocity. This increase on undrained shear strength occurs due to viscous effects. Furthermore, this method has been used to estimate the undrained shear strength of other fine-grained materials such as silts, tailings, among others. Tests results interpretation must to be careful on these materials, because partial drainage can occur during shear tests conducted at the standard field shear rate. In this cases, soil strength and stiffness are higher than under undrained conditions. Thus, this research is aimed to evaluate the influence of the vane shear velocity in soils strength. Vane tests were conducted using vanes with 20.2, 25.5 and 40.0 mm in diameter and with aspect ratio of 2, at rotation rates from 0.68 to 1800o/min using three kaolin-bentonite mixtures composed by 85% kaolin and 15% bentonite with a water content of 100, 130 and 160% (clay), a mixture composed just by kaolin with a 50% water content (silt) and a mixture composed by 60% kaolin and 40% Osório sand with a 40% water content (silt). Tests results shows that clay and silt strength increases with shear rate, under undrained conditions. Undrained shear strength is also influenced by vane diameter and soil void ratio, and consequently by water content. Viscous response on vane tests throughout the undrained range of velocities can be described by a power law (for normalized velocity values further than 10). Silty soils, especially clay-sand mixtures under undrained conditions, exhibited a greater increase on strength than the increased observed for clayey soils. Neverthless, in some tests conducted at low shear velocities, part of pore pressure excess generated during vane rotation was dissipated, occasioning partial drainage effects during shear. The measured torque has been influenced by vane blade dimensions, but any variation on normalized resistance (T/Tref) wasn’t found as a result of vane dimensions. Normalized velocity considers directly peripheral velocity, vane geometry and soil coeficient of consolidation and reflects permeability, stifness and shear rate effects, factors that also control viscous effects. Thus, viscous effects in vane tests are accurately represented on normalized space. In addiction to rate effects due to viscosity evaluation, results normalization on T/Tref versus V space enable partial drainage effects assessment. It shows that the two distinct physical phenomena can be identified and interpreted using one single approach.

This dissertation is devoted to the finite element (FE) approximation of equations describing the motion of a class of non-Newtonian fluids. The main focus is on incompressible fluids whose viscosity nonlinearly depends on the shear rate and pressure. The equations of motion are discretized with equal-order d-linear finite elements, which fail to satisfy the inf-sup stability condition. In this thesis a stabilization technique for the pressure-gradient is proposed that is based on the well-known local projection stabilization (LPS) method. If the viscosity solely depends on the shear rate, the well-posedness of the stabilized discrete systems is shown and a priori error estimates quantifying the convergence of the method are proven. In the shear thinning case, the derived error estimates provide optimal rates of convergence with respect to the regularity of the solution. As is well-known, the Galerkin FE method may suffer from instabilities resulting not only from lacking inf-sup stability but also from dominating convection. The proposed LPS approach is then extended in order to cope with both instability phenomena. Finally, shear-rate- and pressure-dependent viscosities are considered. The Galerkin discretization of the governing equations is analyzed and the convergence of discrete solutions is...

Os ensaios de palheta são frequentemente utilizados na estimativa da resistência não-drenada de depósitos de argilas moles devido à simplicidade do equipamento, rapidez de execução e baixo custo. A velocidade de deformação em ensaios de palheta de campo é, geralmente, de 6º/min. Contudo, os resultados destes ensaios são influenciados por vários fatores e, dentre eles, a velocidade de rotação pode ser considerada um dos mais importantes. Sob condições não-drenadas, os materiais argilosos apresentam ganho de resistência não-drenada com o aumento da velocidade de cisalhamento, resultante da viscosidade da água adsorvida nas partículas de solo. Como o ensaio de palheta tem sido cada vez mais utilizado para estimar a resistência não-drenada de outros solos de granulometria fina, como siltes, resíduos de mineração entre outros, é preciso ter cautela na interpretação dos resultados nestes materiais, pois a utilização da velocidade padrão de campo pode levar à ocorrência de drenagem parcial durante o cisalhamento e, nestes casos, os solos apresentam resistência e rigidez maiores que sob condições não-drenadas. Desta forma, o objetivo deste trabalho consiste na avaliação da influência da velocidade de rotação do ensaio de palheta na resistência dos solos. Foram realizados ensaios de palheta, utilizando palhetas de 20,2, 25,5 e 40,0 mm de diâmetro e com relação altura-diâmetro igual a 2 a velocidades de rotação de 0,68 a 10800o/min, utilizando três misturas compostas por 85% caulim e 15% bentonita com 100, 130% e 160% de umidade (argilosas), uma mistura composta por caulim puro a 50% de umidade (silte) e uma mistura composta por 60% caulim e 40% areia com 40% de umidade (silte). A partir dos resultados dos ensaios de palheta, observou-se que a resistência não-drenada aumenta com a velocidade, sob condições não-drenadas, tanto para os solos argilosos quanto para os siltosos. A resistência não-drenada também é influenciada pelo diâmetro da palheta e pelo índice de vazios do solo, e consequentemente pelo seu teor de umidade. A resposta viscosa dos ensaios de palheta ao longo de toda a faixa não-drenada pode ser descrita por uma equação potencial (para valores de velocidade adimensional maiores que 10). Os solos siltosos, especialmente a argila misturada com areia, também apresentam aumento de resistência com o aumento da velocidade, sob condições não-drenadas, mais pronunciado que para os solos argilosos. Entretanto, a pequenas velocidades, uma parcela do excesso de poro pressão gerado durante a rotação da palheta foi dissipado, ocasionando efeitos de drenagem parcial durante o cisalhamento. O torque medido durante os ensaios é influenciado pelas dimensões da palheta. Porém, não foi verificada qualquer tendência de variação na resistência normalizada (T/Tref) decorrente das dimensões da palheta. A velocidade normalizada (V) considera diretamente, além da velocidade, a geometria da palheta e o coeficiente de adensamento do solo e reflete os efeitos de permeabilidade, rigidez e velocidade de cisalhamento, fatores que também controlam a viscosidade. Desta forma, os efeitos viscosos dos ensaios de palheta são representados com precisão no espaço normalizado. Além da avaliação dos efeitos de velocidade devido a viscosidade, a normalização dos resultados no espaço T/Tref versus V possibilita também a avaliação dos efeitos de drenagem parcial. Ou seja, dois fenômenos físicos distintos podem ser identificados e interpretados utilizando a mesma abordagem. / Vane tests are frequently used to estimate the undrained shear strength of soft clays deposits because of the equipment simplicity, speed and low costs. The strain rate used in vane shear tests is generally of 6o/min. However, vane tests results are influenced by many factors and rate of shear can be considered one of the most important. Under undrained conditions, undrained shear strength of clayey soils increases with shear velocity. This increase on undrained shear strength occurs due to viscous effects. Furthermore, this method has been used to estimate the undrained shear strength of other fine-grained materials such as silts, tailings, among others. Tests results interpretation must to be careful on these materials, because partial drainage can occur during shear tests conducted at the standard field shear rate. In this cases, soil strength and stiffness are higher than under undrained conditions. Thus, this research is aimed to evaluate the influence of the vane shear velocity in soils strength. Vane tests were conducted using vanes with 20.2, 25.5 and 40.0 mm in diameter and with aspect ratio of 2, at rotation rates from 0.68 to 1800o/min using three kaolin-bentonite mixtures composed by 85% kaolin and 15% bentonite with a water content of 100, 130 and 160% (clay), a mixture composed just by kaolin with a 50% water content (silt) and a mixture composed by 60% kaolin and 40% Osório sand with a 40% water content (silt). Tests results shows that clay and silt strength increases with shear rate, under undrained conditions. Undrained shear strength is also influenced by vane diameter and soil void ratio, and consequently by water content. Viscous response on vane tests throughout the undrained range of velocities can be described by a power law (for normalized velocity values further than 10). Silty soils, especially clay-sand mixtures under undrained conditions, exhibited a greater increase on strength than the increased observed for clayey soils. Neverthless, in some tests conducted at low shear velocities, part of pore pressure excess generated during vane rotation was dissipated, occasioning partial drainage effects during shear. The measured torque has been influenced by vane blade dimensions, but any variation on normalized resistance (T/Tref) wasn’t found as a result of vane dimensions. Normalized velocity considers directly peripheral velocity, vane geometry and soil coeficient of consolidation and reflects permeability, stifness and shear rate effects, factors that also control viscous effects. Thus, viscous effects in vane tests are accurately represented on normalized space. In addiction to rate effects due to viscosity evaluation, results normalization on T/Tref versus V space enable partial drainage effects assessment. It shows that the two distinct physical phenomena can be identified and interpreted using one single approach.

A suspension is a fully saturated mixture of discrete solid particles and interstitial liquid. Examples of suspensions include pastes, slurries, cement, food-spreads, drilling fluids and some geophysical flows. The present work focusses on granular (as opposed to colloidal) suspensions, which we define as those for which the thermal motion of the solid particles is negligible. Despite such ubiquity in industry and nature, our understanding of the mechanical properties of suspensions lags behind that of their constituent solid and liquids. In this thesis, the discrete element method is used to simulate suspension flow in shear, capillary and constriction geometries, mapping and characterising the fundamental flow, or rheological, regimes. As a starting point (Chapter 2), we consider an established regime map for dry granular materials, appropriate for flows of sand, grains and dry debris. Taking guidance from shear flow simulations that consider the lubricating effect of an interstitial liquid, we recast the regime map for a general suspension, elucidating flows comparable to the dry material or to a viscous liquid, dependent on the shear rate, liquid viscosity and particle stiffness. We give an account of the microstructural traits associated with each regime. Motivated by recent groundbreaking theoretical, computational and experimental work, we incorporate the emerging picture of frictional shear thickening into our regime map (Chapter 3). Our shear flow simulations capture the shear thickening behaviour and demonstrate that it may, in principle, occur in any of the identified flow regimes. Our simulations of time-dependent shear flows (Chapter 4), specifically flow reversal, provide a detailed micro-mechanical explanation of a longstanding and previously unexplained experimental finding, guiding future experimentalists in decomposing the particle and liquid contributions to the viscosity of any suspension. Indeed, the findings have already been exploited in the devising of an experimental protocol that has successfully proven the dominance of particle contacts in driving shear thickening. We next consider suspension flow in a microchannel (Chapter 5), finding that the identified shear flow regimes are locally applicable to flows in complex geometries under inhomogeneous stress conditions only when the local mean shear rate exceeds temporal velocity fluctuations. A more comprehensive description is therefore required to fully characterise the flow behaviour in this geometry. Finally (Chapter 6), we simulate pressure driven suspension flow through a constriction geometry, observing highly inhomogeneous stress distributions and velocity profiles. The roles of particle and fluid properties are considered in the context of an industrial paste extrusion process.

Os ensaios de palheta são frequentemente utilizados na estimativa da resistência não-drenada de depósitos de argilas moles devido à simplicidade do equipamento, rapidez de execução e baixo custo. A velocidade de deformação em ensaios de palheta de campo é, geralmente, de 6º/min. Contudo, os resultados destes ensaios são influenciados por vários fatores e, dentre eles, a velocidade de rotação pode ser considerada um dos mais importantes. Sob condições não-drenadas, os materiais argilosos apresentam ganho de resistência não-drenada com o aumento da velocidade de cisalhamento, resultante da viscosidade da água adsorvida nas partículas de solo. Como o ensaio de palheta tem sido cada vez mais utilizado para estimar a resistência não-drenada de outros solos de granulometria fina, como siltes, resíduos de mineração entre outros, é preciso ter cautela na interpretação dos resultados nestes materiais, pois a utilização da velocidade padrão de campo pode levar à ocorrência de drenagem parcial durante o cisalhamento e, nestes casos, os solos apresentam resistência e rigidez maiores que sob condições não-drenadas. Desta forma, o objetivo deste trabalho consiste na avaliação da influência da velocidade de rotação do ensaio de palheta na resistência dos solos. Foram realizados ensaios de palheta, utilizando palhetas de 20,2, 25,5 e 40,0 mm de diâmetro e com relação altura-diâmetro igual a 2 a velocidades de rotação de 0,68 a 10800o/min, utilizando três misturas compostas por 85% caulim e 15% bentonita com 100, 130% e 160% de umidade (argilosas), uma mistura composta por caulim puro a 50% de umidade (silte) e uma mistura composta por 60% caulim e 40% areia com 40% de umidade (silte). A partir dos resultados dos ensaios de palheta, observou-se que a resistência não-drenada aumenta com a velocidade, sob condições não-drenadas, tanto para os solos argilosos quanto para os siltosos. A resistência não-drenada também é influenciada pelo diâmetro da palheta e pelo índice de vazios do solo, e consequentemente pelo seu teor de umidade. A resposta viscosa dos ensaios de palheta ao longo de toda a faixa não-drenada pode ser descrita por uma equação potencial (para valores de velocidade adimensional maiores que 10). Os solos siltosos, especialmente a argila misturada com areia, também apresentam aumento de resistência com o aumento da velocidade, sob condições não-drenadas, mais pronunciado que para os solos argilosos. Entretanto, a pequenas velocidades, uma parcela do excesso de poro pressão gerado durante a rotação da palheta foi dissipado, ocasionando efeitos de drenagem parcial durante o cisalhamento. O torque medido durante os ensaios é influenciado pelas dimensões da palheta. Porém, não foi verificada qualquer tendência de variação na resistência normalizada (T/Tref) decorrente das dimensões da palheta. A velocidade normalizada (V) considera diretamente, além da velocidade, a geometria da palheta e o coeficiente de adensamento do solo e reflete os efeitos de permeabilidade, rigidez e velocidade de cisalhamento, fatores que também controlam a viscosidade. Desta forma, os efeitos viscosos dos ensaios de palheta são representados com precisão no espaço normalizado. Além da avaliação dos efeitos de velocidade devido a viscosidade, a normalização dos resultados no espaço T/Tref versus V possibilita também a avaliação dos efeitos de drenagem parcial. Ou seja, dois fenômenos físicos distintos podem ser identificados e interpretados utilizando a mesma abordagem. / Vane tests are frequently used to estimate the undrained shear strength of soft clays deposits because of the equipment simplicity, speed and low costs. The strain rate used in vane shear tests is generally of 6o/min. However, vane tests results are influenced by many factors and rate of shear can be considered one of the most important. Under undrained conditions, undrained shear strength of clayey soils increases with shear velocity. This increase on undrained shear strength occurs due to viscous effects. Furthermore, this method has been used to estimate the undrained shear strength of other fine-grained materials such as silts, tailings, among others. Tests results interpretation must to be careful on these materials, because partial drainage can occur during shear tests conducted at the standard field shear rate. In this cases, soil strength and stiffness are higher than under undrained conditions. Thus, this research is aimed to evaluate the influence of the vane shear velocity in soils strength. Vane tests were conducted using vanes with 20.2, 25.5 and 40.0 mm in diameter and with aspect ratio of 2, at rotation rates from 0.68 to 1800o/min using three kaolin-bentonite mixtures composed by 85% kaolin and 15% bentonite with a water content of 100, 130 and 160% (clay), a mixture composed just by kaolin with a 50% water content (silt) and a mixture composed by 60% kaolin and 40% Osório sand with a 40% water content (silt). Tests results shows that clay and silt strength increases with shear rate, under undrained conditions. Undrained shear strength is also influenced by vane diameter and soil void ratio, and consequently by water content. Viscous response on vane tests throughout the undrained range of velocities can be described by a power law (for normalized velocity values further than 10). Silty soils, especially clay-sand mixtures under undrained conditions, exhibited a greater increase on strength than the increased observed for clayey soils. Neverthless, in some tests conducted at low shear velocities, part of pore pressure excess generated during vane rotation was dissipated, occasioning partial drainage effects during shear. The measured torque has been influenced by vane blade dimensions, but any variation on normalized resistance (T/Tref) wasn’t found as a result of vane dimensions. Normalized velocity considers directly peripheral velocity, vane geometry and soil coeficient of consolidation and reflects permeability, stifness and shear rate effects, factors that also control viscous effects. Thus, viscous effects in vane tests are accurately represented on normalized space. In addiction to rate effects due to viscosity evaluation, results normalization on T/Tref versus V space enable partial drainage effects assessment. It shows that the two distinct physical phenomena can be identified and interpreted using one single approach.

Red blood cells (RBCs) form approximately 40 to 45% of the human blood volume, and their behaviour and characteristics are the main determinant of blood properties, such as viscosity. RBCs are deformable species and stack together under low shear rate to form aggregates or rouleaux. Flowing RBCs migrate away from the wall leaving a cell-depleted layer known as the cell-free layer (CFL). This layer contributes to the blood viscosity and exchange between the RBCs and the target cells: a thinner CFL enhances the exchange process by reducing the diffusion distance. The formation of this CFL, however, is not yet completely understood. The goal of this study is to improve the understanding of the formation of the CFL in the micro-flow. This was accomplished by studying the effects of changing both the flow rate and the microchannel geometry on blood flow in microchannels. In this work, 10% hematocrit human blood suspensions were prepared in native plasma and flowed through poly-dimethylsiloxane (PDMS) microchannels of 100 μm x 34 μm cross-section. Investigation of the flowing cells was performed by using micro particle image velocimetry (μPIV) coupled with a high-speed camera. First, the high-speed camera images were processed with customized Matlab programs to detect and measure the CFL thickness and the RBC aggregates sizes. Second, the blood flow velocity profiles were measured using μPIV in order to determine the actual flow rate, the RBCs’ centerline velocity, and the shear rate. The results showed that the increase in both flow rate and shear rate significantly reduced the CFL thickness and RBC aggregates size. Comparison of the upstream and downstream measurements in the bifurcating microchannel showed that the change in microchannel geometry did not significantly influence CFL thickness and RBC aggregate size, while within the daughter branches, RBCs tended to flow close to the inner wall resulting in an undetectable CFL at the inner wall and in a larger CFL at the outer wall of the branch. These in vitro results quantitatively relate CFL thickness and RBC aggregate size at different shear rates. The findings are of immediate interest regarding the understanding of microcirculation and improved designs of microchips.

No description available.

BACKGROUND: Age-related declines in endothelial function have been well documented with larger declines observed in middle-aged. Passive heat exposure has been shown to be a promising method to improve vascular endothelial health, with sauna specifically being linked to reduced risk of cardiovascular disease. Increases in blood flow and shear rates associated with heat exposure are often considered to have a major influence on the observed improved endothelial function following heat exposure. The magnitude of these changes in response to sauna have not yet been defined. Therefore, the purpose of this study is to quantify and compare the vascular response to an acute bout of sauna heating in young and middle-aged individuals. METHODS: 10 young (24.9 ± 4.2 years, 6 males and 4 females) and 8 middle-aged adults (55.6 ± 3.9 years 4 males and 4 females) underwent 40 min of sauna exposure at 80 oC. Esophageal and intramuscular temperatures were recorded throughout the duration of the experiment. Brachial and superficial femoral artery blood flow, artery diameter, and shear rates were recorded at baseline and following heat exposure. Brachial artery flow-mediated dilation (FMD) was measured at baseline and following 90 min of recovery. RESULTS: Core and muscle temperatures significantly increased by 1.5 ± 0.53 and 1.95 ± 0.70 °C, respectively (P < 0.05) and the magnitude of increase did not differ between young and middle-aged participants (P0.867 and 0.488, respectively). Shear rate increased by 170– 200% (P < 0.001), while blood flow increased by 180–390% (P < 0.001) in the superficial femoral and brachial artery, respectively, in both groups. Importantly, the changes in shear and flow did not significantly differ between young and middle-aged subjects for either artery (P = 0.190–0.899.) Systolic blood pressure (SBP) was significantly reduced from 135.25 ± 17.50 to 122.38 ± 19.7 mmHg (P = 0.017) only in middle-aged participants and a decrease in diastolic blood pressure was observed from 81.6 ± 13.0 mmHg at baseline to 69.8 ± 8.4 mmHg (P < .001). Heat-induced dilation was strongly correlated to baseline endothelial function in the young (R = 0.86, P = 0.006), but not the old (R = 0.22, P = 0.631). CONCLUSIONS: These results indicate that young and middle-aged adults have similar shear-rate and blood flow responses to acute sauna heating, which significantly reduces blood pressure in middle-aged, but not young individuals. Future heat therapy studies may elicit meaningful cardiovascular benefits from lower magnitudes of chronic passive heat stress.

No description available.