Topic
Pulsatile flow
About: Pulsatile flow is a research topic. Over the lifetime, 6278 publications have been published within this topic receiving 149638 citations.
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TL;DR: The ratio of pulsatile to total (steady + pulsatile) external work averaged 10% under control conditions but increased markedly when heart rate slowed, when cardiac output rose, or when arterial distensibility was impaired.
Abstract: External left ventricular work was calculated from records of pressure and flow in the ascending aorta of 1 unanaesthetized and 21 anaesthetized dogs. Work was divided into pulsatile and steady components, the former representing energy lost in vascular pulsations and the latter, energy lost in maintaining steady flow. The ratio of pulsatile to total (steady + pulsatile) external work averaged 10% under control conditions but increased markedly when heart rate slowed, when cardiac output rose, or when arterial distensibility was impaired.
214 citations
TL;DR: It was found that inertial effects dominate the flow field under normal physiological flow rates, and flow models coupled with MRI flow measurements become a noninvasive tool to explain the abnormal dynamics of CSF in related brain disorders as well as to determine concentration and local distribution of drugs delivered into the CSF space.
Abstract: The fluid that resides within cranial and spinal cavities, cerebrospinal fluid (CSF), moves in a pulsatile fashion to and from the cranial cavity. This motion can be measured hy magnetic resonance imaging (MRI) and may he of clinical importance in the diagnosis of several brain and spinal cord disorders such as hydrocephalus, Chiari malformation, and syringomyelia. In the present work, a geometric and hydrodynamic characterization of an anatomically relevant spinal canal model is presented. We found that inertial effects dominate the flow field under normal physiological flow rates. Along the length of the spinal canal, hydraulic diameter was found to vary significantly from 5 to 15 mm. The instantaneous Reynolds number at peak flow rate ranged from 150 to 450, and the Womersle number ranged from 5 to 17. Pulsatile flow calculations are presented for an idealized geometric representation of the spinal cavity. A linearized Navier-Stokes model of the pulsatile CSF flow was constructed based on MRI flow rate measurements taken on a healthy volunteer. The numerical model was employed to investigate effects of cross-sectional geometry and spinal cord motion on unsteady velocity, shear stress, and pressure gradientfields. The velocity field was shown to be blunt, due to the inertial character of the flow, with velocity peaks located near the boundaries of the spinal canal rather than at the midpoint between boundaries. The pressure gradient waveform was found to be almost exclusively dependent on the flow waveform and cross-sectional area. Characterization of the CSF dynamics in normal and diseased states may be important in understanding the pathophysiology of CSF related disorders. Flow models coupled with MRI flow measurements mnay become a noninvasive tool to explain the abnormal dynamics of CSF in related brain disorders as well as to determine concentration and local distribution of drugs delivered into the CSF space.
213 citations
TL;DR: Incubation of the donor vessel with NG-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthesis, or removal of its endothelium by rubbing abolished both the frequency- and the amplitude-dependent effects observed in the detector tissue, indicating that these were mediated by changes in EDRF release.
Abstract: We have dissociated the effects of frequency and amplitude of pulsatile flow on flow-induced release of endothelium-derived relaxing factor (EDRF) using cascade bioassay. Rat aortic segments were b...
213 citations
TL;DR: Numerical results are presented for axial and secondary flow velocity and wall shear stresses with special emphasis on the fluid dynamics in the carotid sinus, of major interest because it is affected preferentially by lesions.
212 citations
TL;DR: The results show that the complex flow in the sinus is affected by the angle variation, and the haemodynamic phenomena, which are important in atherogenesis, are more pronounced in the large angle bifurcation.
211 citations