Analytical study of pulsatile mixed electroosmotic and shear-driven flow in a microchannel with a slip-dependent zeta potential

The escalation of zeta potential by the influence of wall slip for the electrokinetically modulated flow through a microchannel motivates to consider the impact of hydrodynamic slippage upon the zeta or surface potential.The reported study undergoes an analytical exploration of the pulsatile electroosmosis and shear-actuated flow characteristics of a fluid with a Newtonian model through a microchannel with parallel plates by invoking the reliance of a zeta or surface potential on slippage.The linearized Poisson-Boltzmann and momentum equations are solved analytically to obtain the explicit expression of the electrical potential induced in the electrical double layer(EDL),the flow velocity field,and the volumetric flow rate for an extensive span of parameters.The velocity field proximal to the microchannel wall is observed to enhance by an apparent zeta potential,and is further escalated for a thinner EDL and an oscillating electric field with a higher amplitude.However,near the core region of the microchannel,the flow velocity becomes invariant with the EDL thickness.The result shows that the lower wall velocity contributes to the flow velocity along with the electroosmotic body force and the impact of the velocity of the wall underneath diminishes proximal to the upper wall.Moreover,the volumetric flow rate increases when the thickness of the EDL decreases,owing to the influence of the wall slip.However,for thinner EDLs and medium and higher oscillating Reynolds numbers,the volumetric flow rate varies non-monotonously,correlative to the slip-free and slip cases.

Analysis of Etiology,Diagnosis,and Treatment Strategy and Efficacy of Pulsatile Tinnitus Caused by Abnormal Vascular Anatomy

Objective To investigate the etiology,clinical characteristics,diagnosis,and treatment strategies and efficacy of pulsatile tinnitus(PT)caused by vascular anatomy abnormality.Methods The clinical data of 45 patients with PT in our hospital from 2012 to 2019 were collected and retrospectively analyzed.Results All 45 patients had vascular anatomical abnormalities.The patients were divided into 10 categories according to the different locations of vascular abnormalities:sigmoid sinus diverticulum(SSD),sigmoid sinus wall dehiscence(SSWD),SSWD with high jugular bulb,pure dilated mastoid emissary vein,aberrant internal carotid artery(ICA)in the middle ear,transverse-sigmoid sinus(TSS)transition stenosis,TSS transition stenosis with SSD,persistent occipital sinus stenosis,petrous segment stenosis of ICA,and dural arteriovenous fistula.All patients complained of PT synchronous with heartbeat rhythm.Endovascular interventional therapy and extravascular open surgery were used according to the location of the vascular lesions.Tinnitus disappeared in 41 patients,was significantly relieved in 3 patients,and was unchanged in 1 patient postoperatively.Except for one patient with transient headache postoperatively,no obvious complications occurred.Conclusion PT caused by vascular anatomy abnormalities can be identified by detailed medical history and physical and imaging examination.PT can be relieved or even completely alleviated after appropriate surgical treatments.

Surgical treatment of pulsatile tinnitus related to the sigmoid sinus

Objective: Tinnitus-a common clinical symptom-can be categorized into pulsatile tinnitus(PT) and non-PT. Among these, PT is usually associated with sigmoid sinus symptoms, such as sigmoid sinus wall defect or diverticulum, for which various surgical treatments are available. We have discussed the clinical efficacy of surgery for sigmoid sinus-associated PT via the transmastoid approach in this study.Methods: We conducted a retrospective review of 4 patients who underwent surgery for sigmoid sinusassociated PT via the transmastoid approach at Nanjing Drum Tower Hospital from January to December2020. Of these, 2 patients had sigmoid sinus wall defect and 2 had sigmoid sinus diverticulum. Postoperative tinnitus grading and surgical efficacy were determined.Results: After surgery, PT dissolved in 3 patients, while tinnitus significantly decreased in 1 patient.During the follow-up period of 12-18 months, none of the 4 patients showed complications related to increased intracranial pressure or venous sinus thrombosis, and tinnitus symptoms disappeared in 3patients without recurrence, although 1 patient occasionally developed tinnitus. Postoperative thin-slice CTA of the temporal bone indicated that the sigmoid sinus bone wall defect or diverticulum was completely repaired with a thick soft tissue coverage.Conclusion: Surgical repair of sigmoid sinus-associated PT via the transmastoid approach deserves clinical promotion as it exhibited better efficiency while being relatively less invasive.

The Hemodynamic Comparative Study Between Pulsatile and Non-Pulsatile VA ECMO:A Primary Numerical Study

Although pulsatile ECMO,as novel kinds of ECMO,has been attracted more and more attention,the differences of the hemodynamic effects of the pulsatile ECMO on the aorta,the cerebral perfusion,and left ventricular work were still under-investigated.The aim of this study was to clarify the hemodynamic differences of the cardiovascular system between the pulsatile and non-pulsatile VA ECMO.In this study,three ECMO support modes,named as“constant flow mode”,“co-pulse mode”and“counter pulse mode”,were designed.The computational fluid dynamics(CFD)study was carried out.The distribution of the oxygenated blood,the blood velocity vector,the oscillatory shear index(OSI),the relative residence time(RRT),the left ventricular external work(EW),the equivalent left ventricular afterload(EAL)and the energy loss of cardiovascular system(EL)were calculated to compare the hemodynamic differences.The simulation results demonstrate that the oxygenated blood under co-pulse mode was easier to perfuse into the three braches vessels than that under both other modes.In addition,the ECMO under counter pulse mode could also achieve lowest RRT(constant flow mode 220 vs.co-pulse mode 132 vs.counter pulse mode 93).Similarly,the ECMO under counter pulse mode could significantly reduce the left ventricular external work(co-pulse mode 1.51 w vs.constant flow mode 1.44 w and counter pulse mode 1.30 w),left ventricular afterload(constant flow mode 1.03 mmHg·s/ml vs.co-pulse mode 1.67 mmHg·s/ml vs.counter pulse mode 0.82 mmHg·s/ml)and energy loss of arterial system(constant flow mode 0.18 w vs.co-pulse mode 0.50 w vs.counter pulse mode 0.16 w).In short,the ECMO under counter pulse mode could have advantages to the left ventricular unloading.In contrast,the ECMO under co-pulse mode has more benefit to cerebral oxygen perfusion.

Effects of renal artery stenosis on realistic model of abdominalaorta and renal arteries incorporating fluid-structureinteraction and pulsatile non-Newtonian blood flow

The effects of the renal artery stenosis （RAS） on the blood flow and vessel walls are investigated. The pulsatile blood flow through an anatomically realistic model of the abdominal aorta and renal arteries reconstructed from CT-scan images is simulated, which incorporates the fluid-structure interaction （FSI）. In addition to the investigation of the RAS effects on the wall shear stress and the displacement of the vessel wall, it is determined that the RAS leads to decrease in the renal mass flow. This may cause the activation of the renin-angiotension system and results in severe hypertension.

Experimental and numerical study of the effect of pulsatile flow on wall displacement oscillation in a flexible lateral aneurysm model

This study experimentally and numerically investigated the effect of pulsatile flow of different frequencies and outflow resistance on wall deformation in a lateral aneurysm.A method for constructing a flexible aneurysm model was developed,and a self-designed piston pump was used to provide the pulsatile flow conditions.A fluid-structure interaction simulation was applied for comparison with and analysis of experimental findings.The maximum wall displacement oscillation increased as the pulsation frequency and outflow resistance increased,especially at the aneurysm dome.There is an obvious circular motion of the vortex center accompanying the periodic inflow fluctuation,and the pressure at the aneurysm dome at peak flow increased as the pulsatile flow frequency and terminal flow resistance increased.These results could explain why abnormal blood flow with high frequency and high outflow resistance is one of the risk factors for aneurysm rupture.

Bone remodeling in sigmoid sinus diverticulum after stenting for transverse sinus stenosis in pulsatile tinnitus: A case report

BACKGROUND Pulsatile tinnitus(PT)is a potentially disabling symptom that has received increasing attention.Multiple causes of PT have been confirmed by targeted treatment.However,dynamic changes of related structures in PT patients with multiple causes after stenting for ipsilateral transverse sinus stenosis(TSS)have not been previously reported.We report such a case and present postoperative computed tomography venography(CTV)follow-up findings to demonstrate the decreased sigmoid sinus diverticulum and bone remodeling.CASE SUMMARY A 45-year-old man suffered from left-sided PT for 15 years that was occasionally accompanied by headache and dizziness.Pre-operative CTV revealed left-sided sigmoid sinus wall anomalies(SSWAs),TSS,outflow dominance,large posterior condylar emissary vein,and an empty sella turcica.A cerebrospinal fluid pressure of 270 mmH2O was further detected.The sound disappeared immediately after stenting for ipsilateral TSS,with no recurrence during 2 years of follow-up.After the procedure,the patient underwent four consecutive CTV examinations.The diverticulum decreased 6 mo after the procedure with new bone remodeling.The density of the remodeled bone was further increased 1 year later,and a hardened edge was formed 2 years later.CONCLUSION PT associated with SSWAs,TSS,and idiopathic intracranial hypertension can be cured by stenting for TSS alone.And bone remodeling around SSWAs is a more significant finding.

Diploic vein as a newly treatable cause of pulsatile tinnitus: A case report

BACKGROUND Pulsatile tinnitus(PT)is an annoying sound that can be eliminated with targeted treatment of the cause.However,the causes of PT have not been fully elucidated.CASE SUMMARY A 38-year-old woman with right-sided objective PT underwent preoperative computed tomography arteriography and venography(CTA/V).A 3.8 mm vine diploic vein(DV),which passed through the mastoid air cells posteriorly in a dehiscent canal and was continuous with the transverse-sigmoid sinus,was thought to be the causative finding.Four-dimensional flow magnetic resonance(4D flow MR)imaging showed that the blood in the DV flowed toward the transverse-sigmoid sinus.The closer the blood was to the transverse-sigmoid sinus,the higher the velocity.No vortex or turbulence was found in the DV or adjacent transverse sinus.The sound was eliminated immediately after ligation of the DV with no recurrence during a three-month follow-up.No flow signal of the DV was noted on postoperative 4D flow MR.CONCLUSION A DV may be a treatable cause of PT.CTA/V and 4D flow MR could be utilized to determine the morphological and hemodynamic characteristics of the DV.

3D CFD Simulation of Pulsatile Blood Flow in the Human Aorta

A three-dimensional computational fluid dynamics (CFD) simulation of the physiological pulsatile blood flow in the human aortic arch and its three branches has been conducted by using commercial software StarCD. The blood flow, of a peak Reynolds number of 3289 and a Womersley parameter of 16.44, was simulated in a rigid aorta geometry that was built by computer aided design (CAD) reconstruction method based on autopsy data of a female adult. The purpose of this work is to further the understanding of the complex nature of aorta flow, therefore it mainly focuses on analysis of the spatial and temporal distributions of velocities and wall shear stresses. The results, illustrated by 3D visualization pictures and 2D graphs of the primary velocity profiles, wall shear stress and pressure distributions, as well as the secondary flow patterns, are in good agreement with those of other experimental and computational works. The distributions of pressure and wall shear stress support the correlation between high and low shear stresses and pressures and the atherosclerotic lesions.

Transfer characteristics of dynamic biochemical signals in non-reversing pulsatile flows in a shallow Y-shaped microfluidic channel: signal filtering and nonlinear amplitude-frequency modulation

The transports of the dynamic biochemical signals in the non-reversing pulsatile flows in the mixing microchannel of a Y-shaped microfluidic device are ana- lyzed. The results show that the mixing micro-channel acts as a low-pass filter, and the biochemical signals are nonlinearly modulated by the pulsatile flows, which depend on the biochemical signal frequency, the flow signal frequency, and the biochemical signal transporting distance. It is concluded that, the transfer characteristics of the dynamic biochemical signals, which are transported in the time-varying flows, should be carefully considered for better loading biochemical signals on the cells cultured on the bottom of the microfluidic channel.

EFFECT OF THE MAGNETIC FIELD ON THE PULSATILE FLOW THROUGH A RIGID TUBE

This study presents the effect of the magnetic field with constant intensity on the pulsatile flow through a rigid tube. Basing on the experimental results, the influence of the magnetic field on the blood viscosity is considered The analytic solution of the pulsatile flow through a rigid tube under constant magnetic field intensitier and the effect of the magnetic field on the velocity distribution, flow and impedance in a rigid tube are given. this investigation is valuable for understanding the influence of the magnetic field on the blood circulation.

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.

THE INFLUENCE OF LOW-FREQUENCY VARYING MAGNETIC FIELDON THE PULSATILE FLOW IN A RIGID ROUND TUBE

In this paper, the analytic solution of the dynamical equation of the pulsatile flow in a rigid round tube under the low-frequency varying magnetic field is obtained. The velocity distribution and the flow impedance are calculated. The results of e valuable for understanding the influence of low-frequency varying magnetic field on hemodynamics and its clinical application.

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.

Pulsatile electroosmotic flow of a Maxwell fluid in a parallel flat plate microchannel with asymmetric zeta potentials

The pulsatile electroosmotic flow （PEOF） of a Maxwell fluid in a parallel flat plate microchannel with asymmetric wall zeta potentials is theoretically analyzed. By combining the linear Maxwell viscoelastic model, the Cauchy equation, and the electric field solution obtained from the linearized PoissomBoltzmann equation, a hyperbolic par- tial differential equation is obtained to derive the flow field. The PEOF is controlled by the angular Reynolds number, the ratio of the zeta potentials of the microchannel walls, the electrokinetic parameter, and the elasticity number. The main results obtained from this analysis show strong oscillations in the velocity profiles when the values of the elas- ticity number and the angular Reynolds number increase due to the competition among the elastic, viscous, inertial, and electric forces in the flow.

A pilot study of a novel pulsatile flow generator using large collapsible bladder

Background: There are different experimental models avialable for generating pulsatile flow in laboratory and study their heamodynamic effects on blood vessels. We aim to produce a novel pulsatile flow generator utilizing a large collapsible rubber bladder and the phenomenon of fluid structure interactions occurring in a specially designed flexible tube arrangement. Mehtods: Water enters from a reservoir above into a large collapsible bladder made of rubber which opens into ‘U’ shaped tube made of flexible material and held by non rigid structures. As liquid starts flowing the distal end of collapsible bladder collapses under the negative atmospheric pressure generated inside closing the mouth of ‘U’ shaped tube and produces pulsatile flow. Resuts: The frequency of pulsations, pressure fluctuations and velocity profile resemble that of in vivo blood flow. As the flow entering into collapsible bladder increases the frequency of pulsatile flow decreases and also when height of the collapsible bladder from the ground was changed. The whole cycle of alternate collapse/expansion of collapsible bladder with generation of pulsatile flow continue indefinitely as long as there is enough water in reservoir and vertical gradient to sustain the flow. Conclusions: The pulsatile flow so produced has many of the characteristics of physiological blood flow and can be used to study mechanisms of various cardiovascular diseases in laboratory.

Numerical Study of Slip Effect of Unsteady MHD Pulsatile Flow through Porous Medium in an Artery Using Generalized Differential Quadrature Method (Comparative Study)

The unsteady pulsatile flow of blood through porous medium in an artery has been studied under the influence of periodic body acceleration and slip condition by considering blood as incompressible Newtonian electrically conducting fluid in the presence of magnetic field. In this paper, a new technique of differential quadrature method is introduced to find numerical solution of non-linear partial differential equations such as the equation of motion of this problem “Navier-Stokes equation”. The presence of the nonlinearity in the problem leads to severe difficulties in the solution approximation. In construction of the numerical scheme “a new algorithm” a generalized differential quadrature method (GDQM) is to use for derivatives with respect to space variables of differential equations and for the time derivative applying fourth order RungeKutta Method (RKM). The GDQM changed the nonlinear partial differential equations into a system of nonlinear ordinary differential equations (ODEs). The obtained system of ODEs is solved by 4th order RKM. This combination of DQM and 4th order RKM gives a very good numerical technique for solving time dependent problems. The algorithm is coded in Matlab 7.14.0.739 and the simulations are run on a Pentium 4 CPU 900 MHz with 1 GB memory capacity. The effects of slip condition, magnetic field, porous medium, and body acceleration have been discussed. The numerical results show that the proposed method is more accurate and convergent than other numerical methods in literature. The method is illustrated and compared with the exact and analytical solutions and it is found that the proposed method gives a better accuracy and is quite easy to implement.

Maintenance of High Blood Pressure and Early Establishment of Pulsatile Blood Flow to the Spinal Cord during Thoracoabdominal Aortic Repair

Objectives: Despite continuous advancements in the surgical treatments for thoracoabdominal aortic aneurysms (TAAA), paraplegia remains a devastating treatment-related complication. We aimed to summarize our experience with a novel surgical strategy involving maintenance of high blood pressure and early establishment of pulsatile blood flow to the spinal cord. Materials and Methods: Between August 2011 and October 2017, 29 patients (age, 67 ± 12 years) underwent open surgery for TAAA. According to the Crawford classification, two aneurysms were type I, eight were type II, 12 were type III, and seven were type IV. We used partial cardiopulmonary bypass under mild hypothermia in all patients except one. By maintaining distal aortic perfusion pressure at 60 - 80 mmHg and creating the distal aortic anastomosis before visceral branch reconstruction, we established early perfusion of the hypogastric arteries with native pulsatile flow. Intraoperative spinal monitoring and cerebrospinal fluid drainage were performed in 26 (90%) and 23 (79%) patients, respectively. Nineteen patients (66%) underwent reconstruction of the intercostal arteries. During perioperative management, the mean arterial pressure was kept >80 mmHg. Results: No in-hospital deaths or acute neurological complications occurred. One patient (3.4%) experienced delayed temporal paraplegia. During follow-up, aorta-related death occurred in only one patient, who developed prosthetic vascular graft infection but did not undergo repeat graft replacement. The 3-year freedom from aortic-related death was 95%. Conclusion: Our surgical strategy involving maintenance of high blood pressure and early establishment of pulsatile flow to the spinal cord was effective in preventing spinal cord injury following open surgery for TAAA.

Mathematical Analysis on Pulsatile Flow through a Catheterized Stenosed Artery

In this paper, the pulsatile flow of blood through an inclined catheterized stenosed artery is analyzed. Perturbation method is used to solve the implicit system of partial differential equations with suitable boundary conditions. Various analytical expressions axial velocity, flow rate, wall shear stress and effective viscosity have been derived with the help of MATLAB for understanding the fluid flow phenomena. The combined effect of catheterization, body acceleration, slip and inclination has been seen by plotting the graph and observed that axial velocity and flow rate increases with the increase in body acceleration, inclination angle and slip velocity while axial velocity diminishes on increasing the catheter radius. Wall shear stress increases with the increase in catheter radius and body acceleration but presence of slip velocity reduces the wall shear stress. Effective viscosity diminishes on increasing body acceleration and inclination angle, whereas slightly augmented in non-inclined stenosed artery.

Durable response to pulsatile icotinib for central nervous system metastases from EGFR-mutated non-small cell lung cancer: A case report

BACKGROUND Central nervous system(CNS) metastases are a catastrophic complication of nonsmall cell lung cancer(NSCLC), including brain and leptomeningeal carcinomatosis, and are always accompanied by a poor prognosis. Despite the continuous development of existing treatments, the therapy of CNS metastases remains challenging.CASE SUMMARY We report a patient who was definitively diagnosed with brain and leptomeningeal metastases from NSCLC with a targeted mutation in epidermal growth factor receptor(EGFR). A standard dosage of icotinib(125 mg three times daily) was implemented but ineffective. CNS lesions developed despite stable systemic control, so pulsatile icotinib(1125 mg every 3 d) was administered. This new strategy for administration has lasted 25 mo so far, and resulted in complete remission of neurological symptoms, almost vanished lesions, and longer survival with no notable side effects.CONCLUSION This is the first successful example of pulsatile icotinib for treating isolated CNS progression from EGFR mutation-positive NSCLC, providing a new alternative for the local treatment of CNS metastases.