Hydrothermal analysis on non-Newtonian nanofluid flow of blood through porous vessels

In this paper, the flow of non-Newtonian blood fluid with nanoparticles inside a vessel with a porous wall in presence of a magnetic field have been investigated. This study aimed to investigate various parameters such as magnetic field and porosity on velocity, temperature, and concentration profiles. In this research, three different models (Vogel, Reynolds and Constant) for viscosity have been used as an innovation. The governing equations are solved by Akbari-Ganji's Method (AGM) analytical method and the Finite Element Method (FEM) is used to better represent the phenomena in the vessel. The results show that increasing the Gr number, porosity and negative pressure increase the blood velocity and increasing the magnetic field intensity decrease the blood velocity.

Aging-related cerebral microvascular changes visualized using ultrasound localization microscopy in the living mouse

Aging-related cognitive decline is an emerging health crisis; however, no established unifying mechanism has been identified for the cognitive impairments seen in an aging population. A vascular hypothesis of cognitive decline has been proposed but is difficult to test given the requirement of high-fidelity microvascular imaging resolution with a broad and deep brain imaging field of view, which is restricted by the fundamental trade-off of imaging penetration depth and resolution. Super-resolution ultrasound localization microscopy (ULM) offers a potential solution by exploiting circulating microbubbles to achieve a vascular resolution approaching the capillary scale without sacrificing imaging depth. In this report, we apply ULM imaging to a mouse model of aging and quantify differences in cerebral vascularity, blood velocity, and vessel tortuosity across several brain regions. We found significant decreases in blood velocity, and significant increases in vascular tortuosity, across all brain regions in the aged cohort, and significant decreases in blood volume in the cerebral cortex. These data provide the first-ever ULM measurements of subcortical microvascular dynamics in vivo within the context of the aging brain and reveal that aging has a major impact on these measurements.

Study on the Radial Sectional Velocity Distribution and Wall Shear Stress Associated With Carotid Artery Stenosis

BackgroundAtherosclerosis is an important cause of cardiovascular disease. The wall shear stress (WSS) is one of the key factors of plaque formation and dislodgement. Currently, WSS estimation is based on measurement of the blood velocity gradient. However, due to the lack of flow field measurements in carotid stenosis vessels, the two distribution forms (parabolic and non-parabolic) commonly considered in numerical simulations could cause WSS estimates to differ by more than 40%, which could seriously affect the accuracy of mechanical analysis. MethodsThis study was the first to apply 3D printing technology to create an experimental model of real-structure carotid arteries. Microparticle image velocimetry (micro-PIV) was adopted to comprehensively measure blood velocity field data at the stenosis location, providing experimental validation of numerical simulation (Fluent; finite volume method) results. Then, the flow field was simulated at a normal human heart rate (45-120 beats per minute). ResultsThis study revealed that when blood flowed across the carotid artery stenosis location, the velocity distribution was not parabolic but rather a plateau-shaped distribution, with a similar flow velocity in the central area (more than 65% of the total flow path). The WSS values calculated based on a parabolic velocity distribution and the maximum velocity were nearly 60% lower.ConclusionThis study provides a reliable method for WSS determination to better understand the vascular stenosis location and facilitate flow and shear force field research. In the future, it is necessary to carry out in-depth research on the relationship between the plaque shape, flow field distribution and WSS, and amendments to the calculated WSS for clinical stenosis should be proposed.

Cerebrovascular Response to an Acute Bout of Low-Volume High Intensity Interval Exercise and Recovery in Young Healthy Adults

Introduction: High intensity interval exercise (HIIT) is performed widely. However, there is a gap in knowledge regarding the acute cerebrovascular response to low-volume HIIT. Our objective was to characterize the middle cerebral artery blood velocity (MCAv) response during an acute bout of low-volume HIIT in young healthy adults. We hypothesized MCAv would decrease below baseline (BL) 1) during HIIT, 2) immediately following HIIT, 3) and 30-minutes after HIIT. As a secondary objective, we investigated sex differences in the MCAv response during HIIT. Methods: Twenty-four young healthy adults completed HIIT (12 male, age 25 (SD 2)). HIIT included 10-minutes of 1-minute high intensity (~70% estimated maximal watts) and active recovery (10% estimated maximal watts) intervals on a recumbent stepper. MCAv, mean arterial pressure (MAP), heart rate (HR), and end tidal carbon dioxide (PETCO2), were recorded at BL, during HIIT, immediately following HIIT, and 30-minutes after HIIT. Results: Contrary to our hypothesis, MCAv remained above BL during HIIT. MCAv peaked at minute 3 then decreased concomitantly with PETCO2. MCAv was lower than BL immediately following HIIT (p < 0.001). Thirty-minutes after HIIT, MCAv returned to BL (p = 0.47). Compared to men, women had a higher MCAv at BL (p = 0.001), during HIIT (p = 0.009), immediately following HIIT (p = 0.004) and 30-minutes after HIIT (p = 0.001). Conclusions: MCAv did not decrease below BL during low-volume HIIT. However, MCAv decreased below BL immediately following HIIT and returned to resting values 30-minutes after HIIT. MCAv also differed between sex.

Computational analysis of aortic haemodynamics in the presence of ascending aortic aneurysm

BACKGROUND: The usefulness of numerical modelling of a patient’s cardiovascular system is growing in clinical treatment. Understanding blood flow mechanics can be crucial in identifying connections between haemodynamic factors and aortic wall pathologies. OBJECTIVE: This work investigates the haemodynamic parameters of an ascending aorta and ascending aortic aneurysm in humans. METHODS: Two aortic models were constructed from medical images using the SimVascular software. FEM blood flow modelling of cardiac cycle was performed using CFD and CMM-FSI at different vascular wall parameters. RESULTS: The results showed that highest blood velocity was 1.18 m/s in aorta with the aneurysm and 1.9 m/s in healthy aorta model. The largest displacements ware in the aorta with the aneurysm (0.73 mm). In the aorta with the aneurysm, time averaged WSS values throughout the artery range from 0 Pa to 1 Pa. In the healthy aorta, distribution of WSS values changes from 0.3 Pa to 0.6 Pa. CONCLUSIONS: In the case of an ascending aortic aneurysm, the maximum blood velocity was found to be 1.6 times lower than in the healthy aorta. The aneurysm-based model demonstrates a 45% greater wall displacement, while the oscillatory shear index decreased by 30% compared to healthy aortic results.