scholarly journals Effect of Variable Viscosity on MHD Inclined Arterial Blood Flow with Chemical Reaction

2018 ◽  
Vol 23 (3) ◽  
pp. 767-785 ◽  
Author(s):  
B. Tripathi ◽  
B.K. Sharma
Keyword(s):  
Magnetic Field ◽  
Blood Flow ◽  
Shear Stress ◽  
Chemical Reaction ◽  
Applied Magnetic Field ◽  
Variable Viscosity ◽  
Arterial Blood Flow ◽  
Concentration Profiles ◽  
Arterial Blood ◽  
Magnetic Field Increase

Abstract In this paper, we present the mathematical study of heat and mass transfer effects on an arterial blood flow under the influence of an applied magnetic field with chemical reaction. A case of mild stenosis is considered in a non-tapered artery which is inclined at an angle γ from the axis. The variable viscosity of the blood is considered varying with the hematocrit ratio. Governing non-linear differential equations have been solved by using an analytical scheme, homotopy perturbation method to obtain the solution for the velocity, temperature and concentration profiles of the blood flow. For having an adequate insight to blood flow behavior through a stenosed artery, graphs have been plotted for wall shear stress, velocity, temperature and concentration profiles with varying values of the applied magnetic field, chemical reaction parameter and porosity parameter. The results show that in an inclined artery, the magnitude of the wall shear stress at stenosis throat increases as values of the applied magnetic field increase while it reduces as the values of both the chemical reaction and porosity parameters increase. Contour plots have been plotted to show the variations of the velocity profile of blood flow as the values of the height of the stenosis as well as the influence of the applied magnetic field increase.

A model of anemic tissue perfusion after blood transfusion shows critical role of endothelial response to shear stress stimuli

2021 ◽  
Author(s):  
Weiyu Li ◽  
Amy G. Tsai ◽  
Marcos Intaglietta ◽  
Daniel M. Tartakovsky
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Blood Transfusion ◽  
Critical Role ◽  
Cardiovascular Responses ◽  
Arterial Blood Flow ◽  
Microvascular Blood Flow ◽  
No Production ◽  
Arterial Blood ◽  
Transfusion Requirements

­­ ­Although some of the cardiovascular responses to changes in hematocrit (Hct) are not fully quantified experimentally, available information is sufficient to build a mathematical model of the consequences of treating anemia by introducing RBCs into the circulation via blood transfusion. We present such a model, which describes how the treatment of normovolemic anemia with blood transfusion impacts oxygen (O2) delivery (DO2, the product of blood O2 content and arterial blood flow) by the microcirculation. Our analysis accounts for the differential response of the endothelium to the wall shear stress (WSS) stimulus, changes in nitric oxide (NO) production due to modification of blood viscosity caused by alterations of both hematocrit (Hct) and cell free layer thickness, as well as for their combined effects on microvascular blood flow and DO2. Our model shows that transfusions of 1- and 2-unit of blood have a minimal effect on DO2 if the microcirculation is unresponsive to the WSS stimulus for NO production that causes vasodilatation increasing blood flow and DO2. Conversely, in a fully WSS responsive organism, blood transfusion significantly enhances blood flow and DO2, because increased viscosity stimulates endothelial NO production causing vasodilatation. This finding suggests that evaluation of a patients' pre-transfusion endothelial WSS responsiveness should be beneficial in determining the optimal transfusion requirements for treating anemic patients.

scholarly journals Hemodynamic Shear Stress and Endothelial Dysfunction in Hemodialysis Access

2014 ◽  
Vol 7 (1) ◽  
pp. 33-44 ◽  
Author(s):  
Michelle K Fitts ◽  
Daniel B Pike ◽  
Kasey Anderson ◽  
Yan-Ting Shiu
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Neointimal Hyperplasia ◽  
Vascular Wall ◽  
Chronic Hemodialysis ◽  
Arterial Blood Flow ◽  
Venous Anastomosis ◽  
Arterial Blood ◽  
Arteriovenous Access ◽  
The Impact

Surgically-created blood conduits used for chronic hemodialysis, including native arteriovenous fistulas (AVFs) and synthetic AV grafts (AVGs), are the lifeline for kidney failure patients. Unfortunately, each has its own limitations; AVFs often fail to mature to become useful for dialysis and AVGs often fail due to stenosis as a result of neointimal hyperplasia, which preferentially forms at the graft-venous anastomosis. No clinical therapies are currently available to significantly promote AVF maturation or prevent neointimal hyperplasia in AVGs. Central to devising strategies to solve these problems is a complete mechanistic understanding of the pathophysiological processes. The pathology of arteriovenous access problems is likely multi-factorial. This review focuses on the roles of fluid-wall shear stress (WSS) and endothelial cells (ECs). In arteriovenous access, shunting of arterial blood flow directly into the vein drastically alters the hemodynamics in the vein. These hemodynamic changes are likely major contributors to non-maturation of an AVF vein and/or formation of neointimal hyperplasia at the venous anastomosis of an AVG. ECs separate blood from other vascular wall cells and also influence the phenotype of these other cells. In arteriovenous access, the responses of ECs to aberrant WSS may subsequently lead to AVF non-maturation and/or AVG stenosis. This review provides an overview of the methods for characterizing blood flow and calculating WSS in arteriovenous access and discusses EC responses to arteriovenous hemodynamics. This review also discusses the role of WSS in the pathology of arteriovenous access, as well as confounding factors that modulate the impact of WSS.

A new method for visualizing pulmonary artery microvasculature using synchrotron radiation pulmonary microangiography: the measurement of pulmonary arterial blood flow velocity in the high pulmonary blood flow rat model

2018 ◽  
Vol 59 (12) ◽  
pp. 1482-1486 ◽  
Author(s):  
Chiho Tokunaga ◽  
Shonosuke Matsushita ◽  
Hiroaki Sakamoto ◽  
Kazuyuki Hyodo ◽  
Misao Kubota ◽  
...  
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Synchrotron Radiation ◽  
Pulmonary Artery ◽  
Rat Model ◽  
Vascular Remodeling ◽  
Pulmonary Blood Flow ◽  
Arterial Blood Flow ◽  
Non Invasive ◽  
Arterial Blood

Background Increased pulmonary blood flow (PBF) and shear stress may provoke irreversible vascular remodeling, yet invasive visualization of the microvasculature complicates monitoring. A non-invasive imaging methodology would therefore safely provide mechanistic insights into the progression of high PBF-induced vascular remodeling. Purpose To establish a novel microvasculature visualization method using synchrotron radiation pulmonary microangiography (SRPA) that can also calculate PBF velocity in vivo. Material and Methods A high PBF rat model was established by making a fistula between the abdominal aorta and inferior vena cava. After eight weeks, SRPA was performed and the dynamic density changes in the right lower pulmonary artery (PA) were calculated by software. SRPA was performed with a HARP (High-Gain Avalanche Rushing amorphous Photoconductor) receiver. PBF velocity was calculated by contrast medium transit time within the PA. All data were presented as mean ± standard error (SE). Student's t-test was used for comparison between the two groups. Results High dynamic spatial and contrast resolution from SRPA in the PA allowed for clear pulmonary microangiography and accurate detection of higher PBF in the rat model (82.3 ± 8.5 mm/s high-PBF group vs. 46.1 ± 4.3 mm/s control group, P < 0.01). Conclusions These novel results demonstrate that SRPA was useful in both visualizing the dynamic flow distribution within the microvasculature and calculating PBF velocity. This newly developed, non-invasive technology may become a powerful tool in clarifying the mechanism of vascular remodeling associated with high PBF-induced shear stress.

scholarly journals Mathematical Modelling of Blood Flow through a Tapered Overlapping Stenosed Artery with Variable Viscosity

2014 ◽  
Vol 11 (4) ◽  
pp. 185-195 ◽  
Author(s):  
G. C. Shit ◽  
M. Roy ◽  
A. Sinha
Keyword(s):  
Magnetic Field ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Pressure Gradient ◽  
Variable Viscosity ◽  
Stenosed Artery ◽  
Flow Through ◽  
Wall Shear ◽  
Analytical Expressions

This paper presents a theoretical study of blood flow through a tapered and overlapping stenosed artery under the action of an externally applied magnetic field. The fluid (blood) medium is assumed to be porous in nature. The variable viscosity of blood depending on hematocrit (percentage volume of erythrocytes) is taken into account in order to improve resemblance to the real situation. The governing equation for laminar, incompressible and Newtonian fluid subject to the boundary conditions is solved by using a well known Frobenius method. The analytical expressions for velocity component, volumetric flow rate, wall shear stress and pressure gradient are obtained. The numerical values are extracted from these analytical expressions and are presented graphically. It is observed that the influence of hematocrit, magnetic field and the shape of artery have important impact on the velocity profile, pressure gradient and wall shear stress. Moreover, the effect of primary stenosis on the secondary one has been significantly observed.

Mechanisms of Abdominal Aortic Aneurysm Formation in Persons With Traumatic Amputation of a Lower Extremity

2011 ◽  
Author(s):  
Alexander V. Smolensky ◽  
Stephanie Clement-Guinaudeau ◽  
Michael K. Larche ◽  
John N. Oshinski ◽  
W. Robert Taylor
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Lower Extremity ◽  
Aortic Aneurysms ◽  
Arterial Blood Flow ◽  
Infrarenal Aorta ◽  
Traumatic Amputation ◽  
Arterial Blood ◽  
Abdominal Aortic ◽  
Retrograde Blood Flow

Abdominal aortic aneurysms (AAA) are a major cause of morbidity and mortality in the US. The incidence of AAA in older Americans approaches 30%. The most common place of AAA is infrarenal abdominal aorta where oscillatory shear stress (OSS) is present. OSS is known to initiate an inflammatory response in the endothelium. It is known that there is up to a 5-fold increase in the occurrence of AAA in individuals with traumatic amputation of a lower extremity. This increased AAA occurrence is unrelated to co-morbid conditions. We recruited 3 healthy volunteers who underwent infrarenal abdominal aortic Magnetic Resonance angiography and phase contrast imaging. These measurements were done at base line and with acute arterial blood flow occlusion to lower extremity with a blood pressure cuff to mimic amputation. The collected data was used to calculate systolic forward and diastolic retrograde blood flow and wall shear stress during cardiac cycle. Our results suggest that mimicking amputation produces a nearly doubling of retrograde blood flow with ∼50% increase of negative WSS. These changes are more pronounced on the contralateral to the “amputation” side. We conclude that lower extremity traumatic amputations may lead to augmentation of OSS in infrarenal aorta causing AAA development.

scholarly journals Differential impact of water immersion on arterial blood flow and shear stress in the carotid and brachial arteries of humans

2017 ◽  
Vol 5 (10) ◽  
pp. e13285 ◽  
Author(s):  
Howard H. Carter ◽  
Angela L. Spence ◽  
Philip N. Ainslie ◽  
Christopher J. A. Pugh ◽  
Louise H. Naylor ◽  
...  
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Water Immersion ◽  
Arterial Blood Flow ◽  
Differential Impact ◽  
Arterial Blood
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