AN ANALYSIS MODEL OF PULSATILE BLOOD FLOW IN ARTERIES

Blood flow in artery was treated as the flow under equilibrium state (the steady flow under mean pressure)combined with the periodically small pulsatile flow.Using vascular strain energy function advanced by Fung,the vascular stress_strain relationship under equilibrium state was analyzed and the circumferential and axial elastic moduli were deduced that are expressed while the arterial strains around the equilibrium state are relatively small, so that the equations of vessel wall motion under the pulsatile pressure could be established here.Through solving both the vessel equations and the linear Navier_Stokes equations,the analytic expressions of the blood flow velocities and the vascular displacements were obtained.The influence of the difference between vascular circumferential and axial elasticities on pulsatile blood flow and vascular motion was discussed in details.

THE STEADY/PULSATILE FLOW AND MACROMOLECULAR TRANSPORT IN T-BIFURCATION BLOOD VESSELS

A numerical analysis of the steady and pulsatile, macromolecular(such as low density lipopotein (LDL), Albumin) transport in T-bifurcation was proposed. The influence of Reynolds number and mass flow ratio etc. parameters on the velocity field and mass transport were calculated. The computational results predict that the blood flow factors affect the macromolecular distribution and the transport across the wall, it shows that hemodynamic play an important role in the process of atherosclerosis. The LDL and Albumin concentration on the wall varies most greatly in flow bifurcation area where the wall shear stress varies greatly at the branching vessel and the atherosclerosis often appears there.

PULSATILE BLOOD FLOW THROUGH A VISCOELASTICITY-TETHERED TUBE OF MILD VARYING CROSS-SECTION

In this paper a mathematical model is developed for the description of the pulsatile blood flow through an axisymmetric artery of mild varying cross-section, taking into account the tethering effect of the sorrounding tissues.Based on the linear Navier-Stokes equation and boundary conditions,a set of differential equa- tions for the modulus of phase velocity,blood velocities,pressure and deformation of the vessel wall are deduced and the numerical solutions are found by utilizing the Runge-Kutta method.The axial velocity profiles and the peak wall shear stresses are given for both mild tapering tube and mild stenosed tube.It is shown that the peak wall shear stresses in the tethered tube are higher than those in the free tube.It is also shown that in a series of previously research work on peak wall shear stresses of varying cross-section vessels the free vessel assumption has the tendency of under assessing the peak wall shear stresses and vice versa for the rigid vessel assumption.

AB036. Pulsatile choroidal blood flow (PCBF) in the glaucoma spectrum-preliminary results obtained with a novel optical method

Background:Decrease of ocular blood flow has been linked to the pathogenesis of ocular diseases such as glaucoma and age-related macular degeneration.Current methods that measure the pulsatile blood flow have major limitations,including the assumption that ocular rigidity is the same in all eyes.Our group has recently developed a new method to measure the pulsatile choroidal volume change by direct visualization of the choroid with OCT imaging and automated segmentation.Our goal in this study is to describe the distribution of PCBF in a healthy Caucasian population.Methods:Fifty-one subjects were recruited from the Maisonneuve-Rosemont Hospital Ophthalmology Clinic and underwent PCBF measurement in one eye.The distribution of PCBF in healthy eyes was assessed.Results:The distribution of PCBF among the healthy eyes was found to be 3.94±1.70µL with this technique.Conclusions:This study demonstrates the normal range of PCBF values obtained in a healthy Caucasian population.This technique could be used for further investigation of choroid pulsatility and to study glaucoma pathophysiology.

AB091.A novel method for the measurement of pulsatile choroidal blood flow based on video-rate OCT imaging and automated segmentation of the choroid:description and reproducibility

Background:Over the years,a variety of non-invasive techniques have been developed to allow the measurement of blood flow in living human eyes.However,none of the existing techniques has yet been adopted in clinical practice due to their limitations and lack of standardization.Moreover,no reliable technique is currently available to measure the pulsatile choroidal blood flow(PCBF).We propose a novel method based on video-rate optical coherence tomography(OCT)imaging and automated segmentation to measure the pulsatile component of choroidal blood flow in vivo,and demonstrate its repeatability.Methods:Adapted from our earlier work(Beaton et al.),this method uses video-rate OCT with enhanced depth imaging and automated segmentation of the choroid to measure the pulsatile choroidal volume change.Imaging is carried out at the fundus for less than a minute at 7 Hz.In each frame,choroidal thickness(CT)is measured by a segmentation algorithm based on graph cuts using an edge-probability weighting scheme.The algorithm computes the CT change corresponding to choroidal filling over the time-series and subsequently derives the pulsatile choroidal volume change through an approximate model of the eye.Fifty-eight subjects were recruited from the Maisonneuve-Rosemont Hospital and PCBF was measured twice in one eye within the same session and by a single examiner.Repeatability was assessed using the Bland-Altman plot and Intraclass correlation coefficient as calculated with SPSS.Results:Two measurements of PCBF were successfully obtained for each eye using our technique.The average measures ICC for choroidal volume change was 0.929(95%CI,0.881,0.958),showing good to excellent repeatability.The Bland-Altman plot and Pearson coefficient(r=0.840,P<0.001)showed agreement and a strong correlation respectively between intra-session measurement of OR in all examined eyes.Conclusions:This study confirms the high repeatability of pulsatile choroidal blood flow measurements obtained with our optical method,allowing further investigation of blood flow in ocular diseases such as glaucoma and AMD.

EFFECTS OF VASCULAR ZERO STRESS STATE ON PULSATILE BLOOD FOLW

In this paper,blood flow in artery was treated as the flow under equilibrium state (the steady flow under mean pressure) combined with the periodically small sulsatile flow.Based on vascular zero stress state ,the pulsatile strains according to the radial and axial displacements of blood vessel were obtained.With the use of Hooke's law,the pulsatile strains and the corresponding Cauchy stresses were connected,so the corresponding wall motion equations could be established here.By solving the linearized Navier Stokes equations,the analytic expressions of the blood flow velocities and the vascular displacements could be obtained,and the in fluence of the circumferential and axial stretch ratio on pulsatile blood flow and vascular motion was discussed in details.

Optimization of parameters of Yi Zhi Chan Tuina manipulation promotes peripheral circulation

OBJECTIVE:To explore the most effective parameters of Yi Zhi Chan Tuina manipulation for improving peripheral blood circulation.METHODS:A total of 45 volunteers were recruited from Pudong district in Shanghai,China,from October to December 2010,and randomly divided into nine groups using computer-generated random numbers.Participants received Yi Zhi Chan Tuina manipulation on Chengjin(BL 56) acupoint;each group received a particular combination of manipulation force and treatment time.We used a two-factor,three-level factorial design to examine the effects of force and treatment time on changes in popliteal artery average volume flow,pulsatility index,and vessel diameter to determine the optimal parameter group.Outcomes were assessed at baseline and after Tuina manipulation by interviewers blind to treatment group status.RESULTS:After manipulation,two of the nine groups showed an increase in popliteal artery volume flow.An inter-participants effect test showed that for main effect of time,F = 0.331,P = 0.720;for main effect of force,F = 2.934,P = 0.066;and for the force-time interaction effect,F = 1.072,P = 0.385,indicating no interaction between force and time.However,a pairwise comparison of the three levels of time showed that a treatment time of 10 min was significantly more effective than that of 2 min(P = 0.024).A pairwise comparison of light force,medium force,and heavy force showed a statistically significant effect for medium force(P = 0.035).CONCLUSION:Yi Zhi Chan Tuina manipulation with vertical force of 9.31 N for 10 min is most effective in improving peripheral circulation.