Interaction of Elastic Vessel Wall and Arterial Blood Flow

点击翻译按钮获取中文摘要

Effects of the elasticity of the vessel walls on the blood flow characteristics are studied in vitro and In vivo using laser-Doppler anemometers (LDA).In in vitro experiments, a flow apparatus was devised to produce a fully developed pulsatile flow of which Reynolds number and frequency parameter can be vaded for the ranges corresponding to those of the blood flow In the human large arteries. The flow tube was chosen to be 15 mm In diameter and 4.3 m long to produce the developed flow for the Reynolds number up to 5000. The pulsatile flow with non zero mean flow rate is generated by a rotating sheath and a slit put at the outlet of the flow tube. The flow velocity was measured by a 2-dimensional LDA system and the velocity profiles over the cross-section of the tube are obtained by traversing the LDA system. The velocity profile obtained under a steady flow condition was well represented by the Poiseuille velocity profile corresponding to the flow rate measured by an electromagnetic fl … More ow meter, which shows the flow was fully developed. The velocity profiles under a pulsatile flow condition showed a flow reversal near the tube wall in the phases of minimum flow although the total flow rate was always positiv during the pulsation period. Inflection points were also observed In the velocity profiles at the acceleration phases. These features of the pulsatile velocity profiles agree well with the theoretical expectations for the unsteady flow of an incompressible fluid through a straight circular cylinder. Elastic tube highly transparent for the measurement with LDA was made from polyurethane and the velocity measurement inside the elastic tube is in progress.In in vivo experiments, pulsation of the blood flow was studied in microvessels of the mesente ry of rats (SHR and WKY) by a fiber-optic laser-Doppler anemometer microscope (FLDAM) in relation to the rheology and the network topology of the microvessels. The phase lag of the microvascular flow relative to the carotid arterial pressure increased with decreasing diameter of arterioles in SHR mesentery, while there was little correlation between them In WKY. The propagation of the flow pulse In arterioles was theoretically treated by a porous tapered elastic tube model simulating the microvascular tree and the experimental results were analyzed based on this model. It was suggested from the model that the difference observed in the flow pulsation between SHR and WKY might be due to the longer arteriolar length and the fewer branch points in the SHR microvasculature than WKY. The velocity of the propagation of the flow pulse was also measured in arterioles with diameters from 10 to 30 mum to estimate the elastic property of single vessels. The propagation velocity was in the order of 10 cm/s and increased with the increasing vessel diameter, which is also consistent with the prediction derived from the porous tapered elastic tube model. Less