In silico analyses of blood flow and oxygen transport in human micro-veins and valves

2022 ◽  
pp. 1-16
Author(s):  
Rajeeva Pandian Navaneeth Krishna ◽  
Abhishek Jain
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Experimental Models ◽  
Vortical Flow ◽  
Venous Flow ◽  
Venous Valves ◽  
Hypoxic Environment ◽  
Oxygen Gradients ◽  
Direct Measurements ◽  
Complex Fluid

BACKGROUND: Almost 95% of the venous valves are micron scale found in veins smaller than 300μm diameter. The fluid dynamics of blood flow and transport through these micro venous valves and their contribution to thrombosis is not yet well understood or characterized due to difficulty in making direct measurements in murine models. OBJECTIVE: The unique flow patterns that may arise in physiological and pathological non-actuating micro venous valves are predicted. METHODS: Computational fluid and transport simulations are used to model blood flow and oxygen gradients in a microfluidic vein. RESULTS: The model successfully recreates the typical non-Newtonian vortical flow within the valve cusps seen in preclinical experimental models and in clinic. The analysis further reveals variation in the vortex strengths due to temporal changes in blood flow. The cusp oxygen is typically low from the main lumen, and it is regulated by systemic venous flow. CONCLUSIONS: The analysis leads to a clinically-relevant hypothesis that micro venous valves may not create a hypoxic environment needed for endothelial inflammation, which is one of the main causes of thrombosis. However, incompetent micro venous valves are still locations for complex fluid dynamics of blood leading to low shear regions that may contribute to thrombosis through other pathways.

Splanchnic hemodynamics in portal-hypertensive rats: measurement with gamma-labeled microspheres

1982 ◽  
Vol 242 (2) ◽  
pp. G156-G160 ◽  
Author(s):  
R. J. Groszmann ◽  
J. Vorobioff ◽  
E. Riley
Keyword(s):  
Blood Flow ◽  
Portal Vein ◽  
Experimental Models ◽  
Hypertensive Rats ◽  
Venous Flow ◽  
Reliable Technique ◽  
Splanchnic Hemodynamics ◽  
Significant Difference ◽  
Normal Rat ◽  
The Difference

A method to quantitate hepatic arterial flow (HA), portal venous flow (PBF), and blood flow through portal-systemic shunts (ShBF) in portal-hypertensive rats is described. This method relies on the injection of two differently radiolabeled microspheres (15 micrometers) into the left ventricle and spleen. To evaluate the usefulness of this technique, studies were performed on normal, cirrhotic, and portal vein-ligated rats anesthetized with ketamine. With this method, PBF is calculated indirectly from the sums of the blood flow of the splanchnic organs that drain into the portal vein. In the portal-hypertensive animals with portal-systemic shunting, this technique allows for the determination of PBF perfusing the liver [hepatic fraction of portal flow (HFP)] and PBF escaping through portal-systemic shunts (ShBF). The portal vein-ligated rats have higher HA flow (0.68 +/- 0.08 ml . min-1 . g-1) and lower HFP (0.08 +/- 0.01 ml . min-1 . g-1) than either the cirrhotic (HA: 0.27 +/- 0.03 ml . min-1 . g-1, P less than 0.01; HFP: 1.20 +/- 0.20 ml . min-1 . g-1, P less than 0.01) or the normal rat (HA: 0.29 +/- 0.06 ml . min-1 . g-1, P less than 0.01; HFP: 1.39 +/- 0.16 ml . min-1 . g-1, P less than 0.01). No significant difference was found between the cirrhotic and normal rats. The ShBF was higher in the portal vein-ligated rats (21.4 +/- 2.8 ml/min) than in the cirrhotic (4.6 +/- 2.5 ml/min, P less than 0.001) or normal rats (0.03 +/- 0.005 ml/min, P less than 0.01). The difference between the cirrhotic and normal animals was also significant (P less than 0.05). This is a simple, rapid, and reliable technique that allows for the quantitation of splanchnic hemodynamics in experimental models with portal hypertension.

scholarly journals A Simple Transient Poiseuille-Based Approach to Mimic the Womersley Function and to Model Pulsatile Blood Flow

Dynamics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 9-17
Author(s):  
Andrea Natale Impiombato ◽  
Giorgio La Civita ◽  
Francesco Orlandi ◽  
Flavia Schwarz Franceschini Zinani ◽  
Luiz Alberto Oliveira Rocha ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Boundary Conditions ◽  
Quadratic Function ◽  
Pulsatile Blood Flow ◽  
Flow Through ◽  
Simplified Analysis ◽  
Function Models ◽  
Flow Reversals

As it is known, the Womersley function models velocity as a function of radius and time. It has been widely used to simulate the pulsatile blood flow through circular ducts. In this context, the present study is focused on the introduction of a simple function as an approximation of the Womersley function in order to evaluate its accuracy. This approximation consists of a simple quadratic function, suitable to be implemented in most commercial and non-commercial computational fluid dynamics codes, without the aid of external mathematical libraries. The Womersley function and the new function have been implemented here as boundary conditions in OpenFOAM ESI software (v.1906). The discrepancy between the obtained results proved to be within 0.7%, which fully validates the calculation approach implemented here. This approach is valid when a simplified analysis of the system is pointed out, in which flow reversals are not contemplated.

scholarly journals Changes in Hepatic Hemodynamics due to Primary Liver Tumours

HPB Surgery ◽  
1996 ◽  
Vol 9 (4) ◽  
pp. 245-248 ◽  
Author(s):  
F. Jakab ◽  
Z. Ráth ◽  
F. Schmal ◽  
P. Nagy ◽  
J. Faller
Keyword(s):  
Hepatocellular Carcinoma ◽  
Blood Flow ◽  
Hepatic Artery ◽  
Hepatic Blood Flow ◽  
Primary Hepatocellular Carcinoma ◽  
Portal Venous Flow ◽  
Venous Flow ◽  
Control Value ◽  
Early Results ◽  
Total Hepatic Blood Flow

Data regarding the afferent circulation of the liver in patients with primary hepatocellular carcinoma are controversial, we have carried out measurement of hepatic arterial and portal venous flow intraoperatively by transit time ultrasonic volume flowmetry. In patients with primary hepatocellular carcinoma the hepatic artery flow increased to 0.55±0.211 compared with the control value of 0.37±0.102 1/min. (p<0.01). The portal venous flow decreased from 0.61±0.212 l/min, to 0.47±l/min. p<0.01). Due to the opposite changes in the afferent circulation the total hepatic blood flow did not change significantly, compared with controls.The ratio of hepatic arterial flow to portal vein flow increased to 1.239±0.246 in patients with hepatocellular carcinoma, which is double of the control value (0.66±0.259 l/min). After resection this ratio did not change.The resection did not alter hepatic artery or portal venous flow significantly, although the total hepatic blood flow decreased significantly (p<0.01).On the basis of our early results it is possible that the ratio of the two circulations may be to deel measured with doppler ultrasound and provide diagnostic information.

Pattern of blood flow in the pulmonary veins of the dog

1965 ◽  
Vol 20 (6) ◽  
pp. 1118-1128 ◽  
Author(s):  
Eugene Morkin ◽  
John A. Collins ◽  
Harold S. Goldman ◽  
Alfred P. Fishman
Keyword(s):  
Blood Flow ◽  
Pulmonary Circulation ◽  
Pulmonary Veins ◽  
Electromagnetic Flowmeter ◽  
Sine Wave ◽  
Left Ventricular ◽  
Mean Flow ◽  
Venous Flow ◽  
Pulmonary Venous Flow ◽  
Atrial Contraction

The pattern of blood flow in the large pulmonary veins was studied in dogs by chronic implantation of sine-wave electromagnetic flowmeters and cineangiographic observations. These revealed that: 1) pulmonary venous flow is continuous and pulsatile with peak rate of flow of approximately twice the mean flow; 2) the initial rapid increase in venous flow occurs 0.10 sec after the onset of ventricular systole, reaching a peak at the time of closure of the A-V valves; 3) left atrial contraction produces a fleeting slowing or reversal of flow; and 4) respiratory variations in pulmonary venous flow follow those in pulmonary arterial flow, beat by beat. The genesis of phasic pulmonary venous flow was investigated by analysis of pressure and flow curves from the two sides of the heart, by consideration of the energy required for left ventricular filling, and by reconstruction of the pulmonary venous flow pulse using a mathematical model of the pulmonary circulation. These three lines of evidence are consistent in indicating that the transmitted right ventricular pressure is the major determinant of the pulmonary venous flow pattern in the dog. pulsatile pulmonary venous flow; pulmonary venous flow; pulmonary circulation; ventricular suction; respiration on pulmonary circulation; pulmonary venous angiography; pulmonary veno-atrial junctions; electromagnetic flowmeter; cineangiography Submitted on November 16, 1964

Computational Fluid Dynamics (CFD) Study of the 4th Generation Prototype of a Continuous Flow Ventricular Assist Device (VAD)

2004 ◽  
Vol 126 (2) ◽  
pp. 180-187 ◽  
Author(s):  
Xinwei Song ◽  
Houston G. Wood ◽  
Don Olsen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Ventricular Assist Device ◽  
Continuous Flow ◽  
Surrounding Tissue ◽  
Assist Device ◽  
Ventricular Assist ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd

The continuous flow ventricular assist device (VAD) is a miniature centrifugal pump, fully suspended by magnetic bearings, which is being developed for implantation in humans. The CF4 model is the first actual prototype of the final design product. The overall performances of blood flow in CF4 have been simulated using computational fluid dynamics (CFD) software: CFX, which is commercially available from ANSYS Inc. The flow regions modeled in CF4 include the inlet elbow, the five-blade impeller, the clearance gap below the impeller, and the exit volute. According to different needs from patients, a wide range of flow rates and revolutions per minute (RPM) have been studied. The flow rate-pressure curves are given. The streamlines in the flow field are drawn to detect stagnation points and vortices that could lead to thrombosis. The stress is calculated in the fluid field to estimate potential hemolysis. The stress is elevated to the decreased size of the blood flow paths through the smaller pump, but is still within the safe range. The thermal study on the pump, the blood and the surrounding tissue shows the temperature rise due to magnetoelectric heat sources and thermal dissipation is insignificant. CFD simulation proved valuable to demonstrate and to improve the performance of fluid flow in the design of a small size pump.

scholarly journals Application of a bounded upwinding scheme to complex fluid dynamics problems

2013 ◽  
Vol 57 (3-4) ◽  
pp. 435-459 ◽  
Author(s):  
V.G. Ferreira ◽  
M.K. Kaibara ◽  
G.A.B. Lima ◽  
J.M. Silva ◽  
M.H. Sabatini ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Complex Fluid ◽  
Dynamics Problems
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