A Dynamic Boundary Condition for the Pulmonary Vasculature

2008 ◽  
Author(s):  
Rachel B. Clipp ◽  
Brooke N. Steele
Keyword(s):  
Blood Pressure ◽  
Boundary Condition ◽  
Blood Flow ◽  
Computational Models ◽  
Vascular System ◽  
Region Of Interest ◽  
Pulmonary Vasculature ◽  
Dynamic Boundary Condition ◽  
Organ Specific ◽  
Specific Geometry

Computational models can be used to predict the blood pressure and blood flow in a region of interest within the vascular system. To provide an accurate model, it is important to consider the organ-specific properties of the region of interest and apply those properties to the model. The pulmonary vasculature has several organ-specific properties, including the vessel compliance, specific geometry and respiratory process [1,2].

Comparison of Three Types of Dynamic Boundary Conditions

2009 ◽  
Author(s):  
Rachel B. Clipp ◽  
Brooke N. Steele
Keyword(s):  
Boundary Conditions ◽  
Computational Models ◽  
Vascular System ◽  
Dynamic Change ◽  
Region Of Interest ◽  
Pulmonary Vasculature ◽  
Dynamic Boundary Conditions ◽  
System A ◽  
Pulmonary System ◽  
Dynamic Boundary

Computational models can be used to predict the blood pressure and blood flow in a region of interest within the vascular system. A computational model includes a region of interest geometry and boundary conditions. The outlet boundary conditions not only need to reflect the downstream network of vessels, but also the dynamic nature of the downstream network. An example of this is the pulmonary vasculature, which has arterioles that dilate and constrict during the respiratory process altering the resistance/impedance of the downstream network [1]. In order to accurately model a system with a dynamic change, such as the pulmonary system, a dynamic boundary condition should be utilized.

Three Dimensional Simulation of Blood Flow in the Small Arteries of a Truncated Vascular System With Three Levels of Bifurcation

2014 ◽  
Author(s):  
Kamil Kahveci ◽  
Bryan R. Becker
Keyword(s):  
Boundary Condition ◽  
Blood Flow ◽  
Blood Vessel ◽  
Velocity Profile ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Vascular System ◽  
Three Dimensional ◽  
Simulation Software ◽  
Small Arteries

Three dimensional blood flow in a truncated vascular system is investigated numerically using a commercially available finite element analysis and simulation software. The vascular system considered in this study has three levels of symmetric bifurcation. Geometric parameters for daughter vessels, such as their diameters and their angles of bifurcation, are specified according to Murray’s law based on the principle of minimum work. The ratio of blood vessel length to diameter is based upon experimental data found in the literature. An experimentally obtained velocity profile, available in the literature, is used as the inlet boundary condition. An outflow boundary model, consisting of a contraction tube to represent the pressure drop of the small arteries, arterioles, and capillaries that would follow the truncated vascular system, is used to specify the boundary condition at the eight outlets. The results show that although the blood flow velocity experiences a sudden decrease after the bifurcation points due to the higher total cross-sectional area of the daughter vessels as compared to the parent vessel, this decrease in velocity is partially recovered due to the tapering of the blood vessels as they approach the next bifurcation point. The results also show that the secondary flow which is typical after the bifurcation of large arteries does not develop after the bifurcation of small arteries due to the presence of laminar blood flow with very low Reynolds number in the small arteries. The numerical model yields pressure distributions and pressure drops along the vascular system that agree quite well with the physiological data found in the literature. Finally, the results show that, immediately following a bifurcation, the blood flow velocity profile is not symmetrical about the longitudinal axes of blood vessel. However, symmetry is recovered as the blood flow proceeds down the vessel.

TEMPORAL AND SPATIAL HETEROGENEITY IN PULMONARY PERFUSION: A MATHEMATICAL MODEL TO PREDICT INTERACTIONS BETWEEN MACRO- AND MICRO-VESSELS IN HEALTH AND DISEASE

2018 ◽  
Vol 59 (4) ◽  
pp. 562-580 ◽  
Author(s):  
A. R. CLARK ◽  
M. H. TAWHAI
Keyword(s):  
Blood Flow ◽  
Spatial Heterogeneity ◽  
Blood Vessels ◽  
Computational Models ◽  
Temporal Dynamics ◽  
Microvascular Blood Flow ◽  
Pulmonary Vasculature ◽  
Pulmonary Vascular Disease ◽  
Pulmonary Perfusion ◽  
Anatomic Structure

Heterogeneity in pulmonary microvascular blood flow (perfusion) provides an early indicator of lung disease or disease susceptibility. However, most computational models of the pulmonary vasculature neglect structural heterogeneities, and are thus not accurate predictors of lung function in disease that is not diffuse (spread evenly through the lung). Models that do incorporate structural heterogeneity have either neglected the temporal dynamics of blood flow, or the structure of the smallest blood vessels. Larger than normal oscillations in pulmonary capillary calibre, high oscillatory stress contribute to disease progression. Hence, a model that captures both spatial and temporal heterogeneity in pulmonary perfusion could provide new insights into the early stages of pulmonary vascular disease. Here, we present a model of the pulmonary vasculature, which captures both flow dynamics, and the anatomic structure of the pulmonary blood vessels from the right to left heart including the micro-vasculature. The model is compared to experimental data in normal lungs. We confirm that spatial heterogeneity in pulmonary perfusion is time-dependent, and predict key features of pulmonary hypertensive disease using a simple implementation of increased vascular stiffness.

Regional neurohypophyseal blood flow and its control in adult sheep

1981 ◽  
Vol 241 (1) ◽  
pp. R36-R43 ◽  
Author(s):  
R. B. Page ◽  
D. J. Funsch ◽  
R. W. Brennan ◽  
M. J. Hernandez
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
White Matter ◽  
Arterial Blood Pressure ◽  
Median Eminence ◽  
Vascular System ◽  
Neural Lobe ◽  
Adult Sheep ◽  
Blood Flows ◽  
Arterial Blood

Regional neurohypophyseal and cerebral blood flows were measured by the radiolabeled microsphere technique in 30 adult sheep under light barbiturate anesthesia. Regional blood flows were determined under basal conditions. The responses of regional blood flow to alterations in arterial PCO2 and to changes in arterial blood pressure wee also determined. In addition, the relationship between regional neurohypophyseal blood flow and neurosecretory activity as judged by plasma arginine vasopressin levels was assessed. Under basal conditions median eminence blood flow averaged 461 ml.100 g-1.min-1 and did not significantly differ from neural lobe blood flow (436 ml.100 g-1.min-1). Blood flow in the neurohypophysis was about 8 times cortical and 16 times white matter blood flow in these animals. Median eminence and neural lobe blood flow proportionately increased far less than regional cortical or white matter blood flow under conditions of hypercarbia. With alteration of arterial blood pressure, regional neurohypophyseal blood flow remained constant beyond the limits of cerebral autoregulation. The neurohypophysis demonstrates a degree of blood flow homeostasis that exceeds that of any other brain area studied. Although the neurohypophysis is a diverticulum of the brain, its vascular system forms a unique functional as well as a unique anatomic unit.

scholarly journals INPUT IMPEDANCE OF AN ARTERIAL TREE MODEL

2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Patrícia Fonseca de Brito Anjos ◽  
Rodrigo Weber dos Santos ◽  
Rafael Alves Bonfim de Queiroz
Keyword(s):  
Boundary Condition ◽  
Blood Flow ◽  
Input Impedance ◽  
Computational Models ◽  
Model Simulation ◽  
Asymmetry Ratio ◽  
Tree Model ◽  
Arterial Tree ◽  
Small Arteries ◽  
Impedance Response

Computational models are used to represent blood flow in large and small arteries and to simulate cardiovascular diseases. Through these models, it is possible to estimate the pressure and blood flow in arterial vessels. However, to reduce the complexity of the model simulation, it is necessary to truncate small arterial domains representing the networks of small arteries and arterioles. At truncation points, the input impedance is used as a boundary condition. This work describes a method based on fractal laws to generate models of arterial trees that represent the truncated arterial districts, and how to calculate the input impedance of these models. The influence of the parameters used in the generation of the arterial tree model on the input impedance is investigated. The results show that the bifurcation exponent and asymmetry ratio most influence the input impedance response of the models.

Lutein Complex Supplementation Increases Ocular Blood Flow Biomarkers in Healthy Subjects

2019 ◽  
Vol 89 (1-2) ◽  
pp. 5-12
Author(s):  
Alon Harris ◽  
Brent Siesky ◽  
Amelia Huang ◽  
Thai Do ◽  
Sunu Mathew ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Diastolic Blood Pressure ◽  
Healthy Subjects ◽  
Ocular Blood Flow ◽  
Capillary Blood ◽  
Post Treatment ◽  
Capillary Blood Flow ◽  
Doppler Imaging ◽  
Retinal Capillary

Abstract. Introduction: To investigate the effects of a lutein complex supplementation on ocular blood flow in healthy subjects. Materials and Methods: Sixteen healthy female patients (mean age 36.8 ± 12.1 years) were enrolled in this randomized, placebo-controlled, double-blinded, two-period crossover study. Subjects received daily an oral dose of the lutein with synergistic phytochemicals complex (lutein (10 mg), ascorbic acid (500 mg), tocopherols (364 mg), carnosic acid (2.5 mg), zeaxanthin (2 mg), copper (2 mg), with synergistic effects in reducing pro-inflammatory mediators and cytokines when administered together in combination) and placebo during administration periods. Measurements were taken before and after three-week supplementation periods, with crossover visits separated by a three-week washout period. Data analysis included blood pressure, heart rate, intraocular pressure, visual acuity, contrast sensitivity detection, ocular perfusion pressure, confocal scanning laser Doppler imaging of retinal capillary blood flow, and Doppler imaging of the retrobulbar blood vessels. Results: Lutein complex supplementation produced a statistically significant increase in mean superior retinal capillary blood flow, measured in arbitrary units (60, p = 0.0466) and a decrease in the percentage of avascular area in the superior (−0.029, p = 0.0491) and inferior (−0.023, p = 0.0477) retina, as well as reduced systolic (−4.06, p = 0.0295) and diastolic (−3.69, p = 0.0441) blood pressure measured in mmHg from baseline. Data comparison between the two supplement groups revealed a significant decrease in systemic diastolic blood pressure (change from pre- to post-treatment with lutein supplement (mean (SE)): −3.69 (1.68); change from pre- to post-treatment with placebo: 0.31 (2.57); p = 0.0357) and a significant increase in the peak systolic velocity (measured in cm/sec) in the central retinal artery (change from pre- to post-treatment with lutein supplement: 0.36 (0.19); change from pre- to post-treatment with placebo: −0.33 (0.21); p = 0.0384) with lutein complex supplement; data analyses from the placebo group were all non-significant. Discussion: In healthy participants, oral administration of a lutein phytochemicals complex for three weeks produced increased ocular blood flow biomarkers within retinal vascular beds and reduced diastolic blood pressure compared to placebo.

Patterns of Cerebral Blood Flow and Systemic Hemodynamics During Arithmetic Processing

2008 ◽  
Vol 22 (2) ◽  
pp. 81-90 ◽  
Author(s):  
Natalie Werner ◽  
Neval Kapan ◽  
Gustavo A. Reyes del Paso
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Time Course ◽  
Doppler Sonography ◽  
Transcranial Doppler Sonography ◽  
Systemic Hemodynamics ◽  
Heart Period ◽  
Blood Flow Velocities ◽  
Flow Velocities

The present study explored modulations in cerebral blood flow and systemic hemodynamics during the execution of a mental calculation task in 41 healthy subjects. Time course and lateralization of blood flow velocities in the medial cerebral arteries of both hemispheres were assessed using functional transcranial Doppler sonography. Indices of systemic hemodynamics were obtained using continuous blood pressure recordings. Doppler sonography revealed a biphasic left dominant rise in cerebral blood flow velocities during task execution. Systemic blood pressure increased, whereas heart period, heart period variability, and baroreflex sensitivity declined. Blood pressure and heart period proved predictive of the magnitude of the cerebral blood flow response, particularly of its initial component. Various physiological mechanisms may be assumed to be involved in cardiovascular adjustment to cognitive demands. While specific contributions of the sympathetic and parasympathetic systems may account for the observed pattern of systemic hemodynamics, flow metabolism coupling, fast neurogenic vasodilation, and cerebral autoregulation may be involved in mediating cerebral blood flow modulations. Furthermore, during conditions of high cardiovascular reactivity, systemic hemodynamic changes exert a marked influence on cerebral blood perfusion.

COMPARISON OF ANTIHYPERTENSIVE EFFECT OF MOXONIDINE VERSUS CLONIDINE IN RENAL FAILURE PATIENTS.

2018 ◽  
Vol 6 (9) ◽  
Author(s):  
DR.MATHEW GEORGE ◽  
DR.LINCY JOSEPH ◽  
MRS.DEEPTHI MATHEW ◽  
ALISHA MARIA SHAJI ◽  
BIJI JOSEPH ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Renal Failure ◽  
Blood Flow ◽  
Blood Vessel ◽  
Blood Vessels ◽  
High Blood Pressure ◽  
Antihypertensive Effect ◽  
The Body ◽  
Ability To Work ◽  
Blood Flows

Blood pressure is the force of blood pushing against blood vessel walls as the heart pumps out blood, and high blood pressure, also called hypertension, is an increase in the amount of force that blood places on blood vessels as it moves through the body. Factors that can increase this force include higher blood volume due to extra fluid in the blood and blood vessels that are narrow, stiff, or clogged(1). High blood pressure can damage blood vessels in the kidneys, reducing their ability to work properly. When the force of blood flow is high, blood vessels stretch so blood flows more easily. Eventually, this stretching scars and weakens blood vessels throughout the body, including those in the kidneys.

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