Significant Pressure Gradient Research Articles

Oscillation and hysteresis characteristics of high-speed duct during TBCC inlet mode transition under mildly throttled condition

This study aims to investigate the intricate dynamic characteristics of the high-speed duct during the over-under Turbine-Based Combined Cycle TBCC inlet mode transition process while operating in an off-design state under throttled conditions. A typical over-under TBCC inlet, designed for a working Mach number range of 0–6 with a transition Mach number of 3.5, is examined through experimental studies in a supersonic wind tunnel with a freestream Mach number of 2.9. The investigation focuses on the complex oscillatory flow and unique hysteresis observed in the mode transition process of the high-speed duct under the mildly throttled condition, utilizing high-speed Schlieren and dynamic pressure acquisition system. The findings reveal that the high-speed duct undergoes four distinct oscillation stages akin to those in a higher throttled state during the mode transition, albeit with smaller dominant frequency and energy. Moreover, an irregular alternating “big/little buzz” mode is observed in the early stage of the large oscillation stage. Notably, the mildly throttled state exhibits three intriguing hysteresis properties compared to the unthrottled and higher throttled states. Firstly, hysteresis is observed in the shock train motion stage in the duct before unstart, along with the corresponding inverse process. Subsequently, hysteresis is noted in the unstart and restart of the high-speed duct, with a smaller hysteresis interval than in the unthrottled state. Finally, the hysteresis characteristics of oscillation mode switching and the corresponding inverse process are explored. Based on the analysis, the first two hysteresis phenomena are associated with the formation and dissipation of the separation bubble. The significant adverse pressure gradient constrains the cross-sectional capacity of the channel, rendering the disappearance of the separation bubble more challenging. The hysteresis in oscillation mode switching is linked to not only the channel cross-sectional capacity but also the state of the incoming boundary layer.

Early structural valve deterioration following transcatheter aortic valve implantation in a patient with Scheie syndrome: a case report

BackgroundScheie syndrome, an attenuated subtype of mucopolysaccharidosis type I, is a rare storage disease that causes progressive glycosaminoglycans (GAGs) accumulation. Cardiovascular disorders determine the prognosis, and cardiac valve abnormalities are the most common cause. The patients are usually young so mechanical valve replacement is often performed, but because of the features of this disease, the surgical treatment is very risky. Recently, transcatheter aortic valve implantation (TAVI) has been reported as an alternative choice for aortic stenosis, but optimal choice is still unclear. Here, we introduce a patient that underwent TAVI and refer to the histological finding of a biological valve extracted in relation to GAGs accumulation.Case presentationA 54-year-old woman with Scheie syndrome underwent valve surgeries three times throughout her whole life. At age 41, she received a mitral valve replacement with a mechanical valve for mitral stenosis. She promptly developed severe diastolic dysfunction and low output syndrome after the release of aortic clamping, thus requiring temporary mechanical circulatory support4. At age 51, she suffered from heart failure due to severe aortic stenosis and underwent TAVI because conventional aortic valve replacement (AVR) was deemed too risky. Three years later, her heart failure relapsed, and an echocardiogram unexpectedly revealed thickened bioprosthetic valve leaflets and a significant pressure gradient across the valve, consistent with early structural valve deterioration. AVR was performed via median sternotomy with a mechanical valve. As with the first operation, she presented refractory heart failure requiring mechanical circulatory support and was meticulously managed. However, she steadily showed worsening of multiple organ systems and died 9 days after the operation. Pathological autopsy and histological examination revealed accumulation of tissue with GAGs on the leaflets of the bioprosthetic valve of TAVI, which may have been the cause of early structural valve deterioration.ConclusionFor patients with Scheie syndrome, a biological valve can be compromised by the accumulation of GAGs, thereby causing early SVD. These findings may support valve selection for these high-risk patients.

Flow characteristics and performance optimization of temperature and pressure reducing valve with droplets evaporation

The influence of water spray arrangement on temperature reduction performance is significant in temperature and pressure reducing valves (TPRV). A verified vapor-liquid two-phase flow in TPRV was established by Euler-Lagrange flow and droplets evaporation model. The heat and mass transfer processes in droplet evaporation are presented. The influence of nozzles number, spray position, injection direction on internal flow characteristics and temperature reduction performance of TPRV was analyzed. An optimized spray water arrangement was determined via nonlinear fitting model, the great temperature reduction performance was obtained. The results show that the mass flow rate of TPRV inlet and outlet has a non-linear variation with the valve opening. The significant pressure gradient occurs in the valve core and chamber. The upward oblique jet at throat makes the temperature near the spray area low and the temperature at throat downstream high. The range of high Mach numbers increases with the increasing of valve opening. The temperature variation of parallel injection and reverse injection is different with the increasing of the nozzles number. The vortex intensity and range have a stronger influence on temperature reduction performance ability. The temperature reduction performance of optimized TPRV is improved by 0.6 %- 3.98 %. The optimization of water spray arrangement on temperature reduction performance is applicable to various loads.

Compact Eddy Structure of Turbulence Aft of an Inclined Slender Body

The compact eddy structure and the correlation structure of three distinct turbulent boundary layers were investigated, with a view to understanding the turbulent inflow seen by a stern-mounted propulsion tail rotor. The first is of a zero-pressure-gradient, equilibrium, flat plate boundary layer, and the second and third are on the lee and port sides of a body of revolution (BOR) inclined at a 5° angle of attack. The BOR is an axially symmetric body with an ellipsoidal nose, straight midbody, and 1.17-diam-long stern ramp with a stern-mounted tail rotor. Measurements on the BOR were taken at a body-diameter-based Reynolds number of 600,000 and a rotor advance ratio of J=1.27. Particle image velocimetry was taken at two principal locations at the stern of the BOR. Distortion of the correlation function was evident in the compact eddy structure of the BOR boundary layer on both the lee and port sides. On the port side, the turbulent modes were dominated by the embedded shear layer, whereas the lee side showed more significant pressure gradient effects in the eddy structure.

Trans-Clot MAP gradient: A novel innovative technique during thrombectomy for acute ischemic stroke with potential applications for assessing collateral circulation, determining clot etiology, informing device selection, and predicting first-pass success.

Endovascular mechanical thrombectomy has significantly improved recovery in acute ischemic stroke (AIS). While traditional patient selection has relied on factors such as last known well and penumbra volume, emerging research highlights the importance of collateral circulation in influencing thrombectomy success. However, current methods to assess collateral circulation are often unreliable and lack standardization, limiting their integration into clinical decision-making and prompting the need for innovative approaches. This study introduces trans-clot manometry as a promising approach for quantitatively assessing collateral blood flow before thrombectomy. Two patients were included in this study: a 64-year-old female with a left M1 near-complete occlusion and an 81-year-old male with a left P1 occlusion. After receiving intravenous tenecteplase, each patient underwent emergent thrombectomy where intraoperative trans-clot manometry revealed significant trans-clot mean arterial pressure (MAP) gradients (66.7% for Patient 1 and 96.9% for Patient 2). Both patients had successful first-pass thrombectomy (Patient 1: TICI 3; Patient 2: TICI 3), with substantial clinical improvement (Patient 1: NIHSS 11 to 1; Patient 2: NIHSS 19 to 8). Intraoperative trans-clot manometry offers a simple yet powerful, objective, and generalizable measure of collateral circulation, applicable to a wide range of AIS cases regardless of clot location or vessel size. In addition, real-time correlations with heart-rate variability and radial artery pressures provide an intrinsic quality control, ensuring proper execution of the technique and accuracy of the resulting MAP gradient. Future research will focus on validating this approach, determining its generalizability, and establishing MAP gradient thresholds to enhance device selection and predict first-pass success.

Energy and exergy analysis of a novel solar-powered passive multi-stage osmosis desalination system for sustainable water production

Climate change and population growth constantly exacerbate global water scarcity, and seawater desalination technology is crucial to addressing this crisis. Conventional fossil-fuel desalination poses environmental and economic challenges, especially in remote, water-scarce regions. Renewable energy offers sustainable options for seawater desalination; however, most related technologies face challenges in flexible deployment. Among passive technologies, interfacial evaporation still confronts issues of salt accumulation impacting desalination efficiency. Therefore, this study investigates a novel solar-powered passive multi-stage osmosis device that emulates mangroves’ transpiration and natural osmosis processes. Harnessing solar energy, it employs hydrophilic nanoporous membranes for water movement and evaporation and an osmosis membrane for solute retention, aiming for efficient seawater desalination without external power and pressure. Energy and exergy analyses reveal key efficiency factors. Results reveal significant pressure gradients across the osmosis membrane as a challenge. Optimizing salinity and adjusting the area ratio of the nanoporous membrane to the osmosis membrane is vital for stability and performance. Moreover, potential increases in water production from 0.97 kg/m2/h to 3.53 kg/m2/h with a five-stage setup, though benefits diminish with additional stages due to heat/exergy losses. The exergy efficiency increases from 0.14 % for a five-stage device to 0.18 % for a ten-stage system. This study demonstrates the solar-powered passive multi-stage osmosis device’s dependence on solar flux and highlights the importance of optimizing the air gap thickness and insulation to boost efficiency.

Comparison of fluid structure downstream of an evaporative flameholder with subsonic uniform and subsonic-supersonic inflows

Subsonic uniform and supersonic mixing flows are widely present in the combustion chamber of a multi-mode combined scramjet engine, where the significant pressure, velocity, and temperature gradients of the two impose severe limitations on flame propagation. The vortex structures downstream of an evaporative flameholder were experimentally measured under subsonic-supersonic mixing inflow and subsonic uniform inflow. Results indicate that, under subsonic-supersonic mixing inflow conditions, an asymmetric vortex structure in the recirculation zone is formed due to the presence of a subsonic-supersonic shear layer, which exerts compressive or stretching effects on the recirculation zone downstream of the flameholder, in contrast to the symmetric dual-vortex structure observed under subsonic uniform inflow conditions. The asymmetric recirculation zone displays fluid being entrained from one vortex to another, with the degree and direction of entrainment dependent on the supersonic expansion state. Additionally, a simplified flow field structure is proposed for comparing the differences between the subsonic-supersonic mixing inflow and subsonic uniform inflow, along with the introduction of five regions and two stages to describe the flow field structure downstream of the flameholder under subsonic-supersonic mixing inflow. Analysis of the flow characteristics downstream of the flameholder under subsonic-supersonic mixing inflow and subsonic uniform inflow conditions can offer design insights for the combustion scheme of aerospace-integrated propulsion systems.

Fundamental properties of ideal and resistive infernal modes in tokamaks

Infernal modes are unstable in regions of weak magnetic shear and significant pressure gradients. These modes comprise a broad class of instabilities, encompassing interchange modes and kink modes, with both short and long length scales. Toroidal effects and fully electromagnetic fields are of crucial importance for their description. The role of resistive diffusion and compressibility are also critical. In order to investigate this awkward problem while still enabling fundamental physics interpretation, a new resistive MHD eigensolver has been developed. An outcome of this study is the identification of an unstable spectrum of resistive infernal modes in regions of the plasma with weak average curvature, and in regions where the average curvature is destabilising. These fast growing modes may be collectively important for our understanding of global reconnection events, stochastic magnetic fields states, and neighbouring supercritical bifurcations.

Shock–shock interaction on the Reusability Flight Experiment (ReFEx)

AbstractThe Reusability Flight Experiment (ReFEx) is currently under development at the German Aerospace Center (DLR). A coupled experimental and numerical campaign was carried out to investigate the surface heating on the payload geometry during return consisting of a forebody and canard. In this way, numerical tools for a post-flight analysis can be preemptively improved where required. Experiments were undertaken at the High Enthalpy Shock Tunnel Göttingen (HEG) on a 1:4 scale model with the use of temperature sensitive paint on the payload geometry to obtain surface heat flux. The model configuration was varied in angle of attack and canard deflection. Laminar and turbulence-model solvers in the DLR-TAU code were used for the numerical simulations. This investigation focussed on the shock–shock interaction of the nose bow shock with the leading-edge shock of the canards showing significant surface heat flux along the canard. Larger surface heat fluxes were measured in the experiments downstream of the shock interaction on the canard, than obtained from the laminar CFD calculations. This was attributed to transition of the boundary layer within the interaction regions, in the presence of significant adverse pressure gradients. Other flow features along the forebody in the vicinity of the canard were qualitatively matched better by the fully-turbulent numerical solutions than the laminar ones. This work aims to demonstrate the extent to which the numerical and experimental tools assist useful insights into flow phenomena during the return stages of the ReFEx payload geometry, and the aspects for which improvements are required.

Assessing donor-recipient arterial pressure dynamics in STA-MCA bypass for moyamoya disease

BackgroundIn bypass surgery for moyamoya disease (MMD), the superficial temporal artery’s (STA) pressure needs to surpass that of the cortical M4 recipient of the middle cerebral artery (MCA), boosting cerebral blood flow into the MCA and enhancing cerebral circulation. This study investigates the STA-MCA arterial pressure parameters and gradients during bypass surgery, aiming to deepen our understanding of hemodynamic shifts pre- and post-operation.MethodsDSA imaging data were prospectively collected from patients diagnosed with bilateral MMD who underwent STA-MCA bypass surgery between 2022 and 2023 and stratified according to the Suzuki stage. The mean arterial pressure (MAP) of the donor and recipient arteries was directly measured during the STA-MCA bypass procedure, and these data were statistically analyzed and evaluated.ResultsAmong 48 MMD patients, Suzuki grading revealed that 43.8% were in early stages (II and III), while 56.2% were in advanced stages (IV, V, and VI). Predominantly, 77.1% presented with ischemic-type MMD and 22.9% with hemorrhagic type. Pre-bypass assessments showed that 62.5% exhibited antegrade blood flow direction, and 37.5% had retrograde. The mean recipient artery pressure was 35.0 ± 2.3 mmHg, with a mean donor-recipient pressure gradient (δP) of 46.4 ± 2.5 mmHg between donor and recipient arteries. Post-bypass, mean recipient artery pressure increased to 73.3 ± 1.6 mmHg. No significant correlation (r = 0.18, P = 0.21) was noted between δP and Suzuki staging.ConclusionOur study elucidated that cerebral blood pressure significantly decreases beyond the moyamoya network at the distal M4 segment. Furthermore, we observed bidirectional flow in MCA territories and a significant positive pressure gradient between the STA and M4 segments. The lack of correlation between Suzuki stages and M4 pressures indicates that angiographic severity may not reflect hemodynamic conditions before surgery, highlighting the need for customized surgical approaches.

Investigation Of Coastalock Performance On A Breakwater With Porous Core

Hard stabilization methods have traditionally been employed to mitigate coastal erosion. Concrete armour is widely used due to its high level of dependence, robustness, ease of production and cost effectiveness (Cooke et al., 2020; Pikey and Cooper, 2012). It is inevitable that coastline ‘armouring’ will continue to rise because of the growing human population and urbanization, desire for and value of coastal property, opposed to predicted climate change (Chapman and Underwood, 2011). The environmental impact of such 'armouring' on coastal systems can be detrimental, resulting in a degradation or destruction of habitats and the loss of ecologically trivial species (Gittman et al., 2015). The CoastalockTM, a single-layer armour unit, aims to blend coastal protection with marine habitat creation. This armour unit is designed to mimic inter- and sub-tidal habitats, with chemical composition of substrate and micro and macro features that provide niches for various species. The key feature of CoastalockTM is the cavity that is integrated into the design, that caters to diverse marine life needs depending on its orientation (ECOncrete Tech Ltd., 2019). CoastalockTM's hydraulic performance is under research. Preliminary tests conducted in the Hydraulic Engineering Laboratory (HEL) of the Technical University of Delft (TUD) on a 2V:3H impermeable slope in deep water conditions highlighted that with tight placement of the units significant pressure gradients across the top layer led to damage. The introduction of spacings between units for enhanced permeability improved stability significantly (Gutiérrez et al., 2023). A redesign of the unit was proposed incorporating protrusions to enforce the spacings between the blocks (Molenkamp, 2022). This research focuses on evaluating the influence of a porous core on the hydraulic performance of a CoastalockTM armour layer, specifically assessing its stability, overtopping, and reflection on a 2V:3H breakwater slope in deep water conditions—from the toe to just below the crest. A pivotal aspect of this research is the investigation of the impact of protrusions on the hydraulic performance. Furthermore, the study explores the influence of different toe configurations, aiming to comprehend the vulnerability of the armour layer to sliding. Toe scour falls outside the scope of this study.

Flow investigation of two-stand ultrasonic flow meters in a wide dynamic range by numerical and experimental methods

The enhancement of two-stand ultrasonic flow meters relies upon obtaining a precise understanding and prediction of their complex flow physics throughout their entire dynamic range of operation. This study provides a comprehensive numerical and experimental investigation of the flow physics of a typical two-stand ultrasonic flow meter by industry standards. Predictions based on computational fluid dynamics simulations are employed to obtain numerical results, which are validated through experiments based on laser Doppler velocimetry and static pressure drop. Results indicate that no qualitative changes occur beyond an inflow Reynolds number of 104 in terms of coherent structures and flow dynamics. Analysis of the static pressure distribution across cross-sections reveals that the stands are the most influential areas contributing to pressure drop. In cases with turbulent inflow, there is a noticeable recovery of static pressure following significant pressure gradients across the stands, while such recovery is absent in scenarios with laminar inflow. Both numerical and experimental approaches yield excellent agreement in outcomes, accurately estimating the axial velocity within the flow meter’s measurement volume and the pressure drop across it, with deviations within experimental uncertainty ranges of 2 standard deviations. The developed numerical methodology demonstrates its potential to accurately evaluate complex internal-flow systems with similar flow features and Reynolds number ranges. The flow dynamics for a wide dynamic range of operation in two-stand ultrasonic flow meters are shown in detail in both laminar and turbulent flow regimes, displaying rolling vortices, detached flow, and recirculation zones.

Catheter-associated bladder mucosal trauma during intermittent voiding: An experimental study in pigs.

The objective of this study is to characterize bladder mucosal trauma associated with intermittent catheterization with conventional eyelet catheters (CECs) and to assess if a microhole zone catheter (MHZC) design concept reduces this adverse effect. A porcine model was developed to reflect human catheterization and bladder drainage. Nine pigs were randomized for catheterization with CEC (n= 6) or MHZC (n= 3). The bladder was drained repeatedly 20 times through the catheter. Cystoscopy was performed before and after the procedure, and bladders were analysed by histopathology. Two additional pigs were used for cystoscopy visualization of suction events in vivo. Cystoscopy, gross pathology, histopathological score, leucocyte infiltration, and intracatheter pressure at flow stops during voiding were compared for each group. A significant higher pressure gradient was measured inside the CECs compared with MHZCs during flow stop. Consequently, CECs resulted in suction events inflicting bladder trauma characterized by loss of epithelium, oedema, haemorrhage, and neutrophil tissue infiltration. No significant trauma was identified when using MHZC. Considerable mucosal bladder trauma is inflicted by CECs which may be an overlooked risk factor for urinary tract infection. Catheters can be designed to minimize mucosal suction and reduce associated trauma. This may be a solution to reduce infection frequency and increase user comfort. Furthermore, the study demonstrates the potential of pigs as an attractive animal model for investigating urinary catheter performances.

Assessing the results of work on strengthening the soils of the foundation of lock № 5 of the Volga-Don shipping canal and proposals for stabilizing the chamber position

The results of work to strengthen the soil foundation of the chamber of lock № 5 of the Volga-Don Shipping Canal, carried out in 2016–2017, are analyzed. The need to carry out work to strengthen the soil was caused by an increase in the intensity of sedimentation of the central sections of the lock chamber, which began in 2005. To stabilize the chamber position, the technology of two-component jet grouting is implemented. This technology assumes the formation of several longitudinal soil-cement walls in the soils of the lock chamber base, which would transfer the load from the weight of the chamber to the harder clay soils of the water-resistant layer. However, as a result of the work performed, the precipitation intensity has increased. Engineering-geological, hydrological and geophysical studies conducted in 2018–2020 recorded the absence of formed soil-cement elements in the soils of the chamber base. An analysis of the soil samples characteristics taken from the chamber base has showed that a layer of soils of 10–12 m thickness is composed of loess rocks, below which water-resistant clayey rocks lie. Initially, there were several confined and non-confined aquifers in the soils of the lock base, and the creation of a hydroelectric complex and the formation of a level difference between the upper and lower pools led to the formation of a filtration flow with a significant pressure gradient at the base of the chamber. An analysis of the properties and structure of loess soils has showed their predisposition to subsidence, transition to a floating state and liquefaction with an increase in water content. Under the conditions of weak water-saturated loess soils, the supply of a cement mixture into them under significant pressure did not lead to the formation of soil-cement elements. Thus, in accordance with the current regulatory documents, the technical condition of the gateway is defined as pre-emergency, and the security level is defined as unsatisfactory. Methods for reducing the intensity of the chamber sedimentation such as cutting through the loess layer with piles, physical and chemical strengthening of soils and water protection of the massif at the base of the chamber are considered and evaluated.

Link between both infratentorial and supratentorial intracranial pressure burdens and final outcome in patients with infratentorial brain injury.

Increased intracranial pressure (ICP) is most likely not being transmitted uniformly within the cranium. The ICP profiles in the supra- and infratentorial compartments remain largely unclear. Increased ICP in the cerebellum, however, is insufficiently captured by supratentorial ICP (ICPsup) monitoring due to compartmentalization through the tentorium. The authors hypothesized that additional infratentorial ICP (ICPinf) monitoring can be clinically valuable in selected patients. The aims of this study were to demonstrate the safety and feasibility of ICPinf monitoring and to investigate the influence of the ICPinf on clinical outcome in a real-world setting. Fifteen consecutive patients with posterior fossa (PF) lesions requiring surgery and anticipated prolonged neurointensive care between June 2019 and December 2021 were included. Simultaneous ICPsup and ICPinf were recorded. ICP burden was defined as a 15-minute interval with a mean ICP > 22 mm Hg. The Glasgow Outcome Scale score was assessed after 3 months. The mean ICPinf was substantially higher compared with ICPsup throughout the entire period of ICP recording (16.08 ± 4.44 vs 10.74 ± 3.6 mm Hg, p < 0.01). ICPinf was significantly higher in patients with unfavorable outcome when compared with those with favorable outcome (mean 17.2 ± 4.1 vs 11.4 ± 3.5 mm Hg, p < 0.05). Patients with unfavorable outcome showed significantly higher ICPinf burden compared with those with favorable outcome (mean 40.6 ± 43.8 vs 0.3 ± 0.4 hours, p < 0.05). Neither absolute ICPsup nor ICPsup burden was significantly associated with unfavorable outcome (p = 0.13). No monitoring-associated complications occurred. Supplementary ICPinf monitoring is safe and reliable. There is a significant transtentorial pressure gradient within the cranium showing elevated ICPs in the PF. Elevated ICP levels in the PF were strongly associated with unfavorable neurological outcome irrespective of ICPsup values.

Organ blood flow assessment with the ModulHeart cardiorenal support device.

ModulHeart (Puzzle Medical Devices Inc) is a novel percutaneous flow entrainment pump anchored in the descending aorta. The current study evaluates the hemodynamic effect of ModulHeart support and its impact on cerebral, myocardial, and renal blood flow. ModulHeart was implanted in the descending aorta of four healthy calves. A ramp protocol (2000 RPM increments) was performed with the pump operating at five different speeds from 14 000 to 22 000 RPM. For each speed, pressures proximal and distal to the pump, and right heart catheterization measurements were recorded. Stable-isotope labeled microspheres were injected in the left ventricle to evaluate organ perfusion. Thermodilution cardiac output increased by 23% at 22 000 RPM. Greater pump speeds resulted in greater pump gradients, up to 10 mm Hg in mean arterial pressure at 22 000 RPM, without significant reduction of proximal perfusion pressures. Arterial pulse pressure remained stable at all speeds. ModulHeart was not associated with a reduction in cerebral or myocardial blood flow at any speed. Renal cortical and medullary blood flow increased by up to 50% and 40%, respectively. The ModulHeart device implanted in the descending aorta of healthy calves resulted in significant arterial pressure gradients and preserved pulse pressure. Greater pump speeds translated into greater increases in renal blood flow, with no decrease in cerebral or myocardial perfusion.

Endovascular treatment of symptomatic hepatic venous outflow obstruction post major liver resection

PurposeTo evaluate efficacy, safety, and outcomes of endovascular treatment of hepatic vein stenosis post major liver resection.MethodsA retrospective data analysis was performed including all interventional treatments of hepatic vein stenosis post major liver resection since 2010. Post procedural course and clinical parameters including amount of ascites accumulation and relevant laboratory values were assessed during the follow-up period. Primary and primary assisted hepatic venous patency time were calculated.ResultsTwelve patients (median age 55.5, IQR 49.75 to 61.5 years) undergoing a total of 16 interventions were included. Interventions were primary stent placement (n = 3), primary balloon angioplasty (n = 8), three re-interventions and two aborted interventions (no significant pressure gradient). Technical success was 100% (16/16). Permanent reduction and / or complete resolution of ascites was achieved in 72% (8/11). Laboratory parameters related to liver function did not show significant improvement after intervention. Median follow-up period was 6 months (IQR: 1.5 to 18 months). The median primary patency time for patients with balloon angioplasty was 11 months (IQR: 1.375 to 22.25 months) and assisted patency time was 13.25 months (IQR: 4.5 to 22.25 months). The median primary patency time for patients with angioplasty and stent placement was 1 months (IQR: 1.0 to 1.5 months) and assisted patency time was 2.0 months (IQR: 1.5 to 2.5months).ConclusionAn endovascular approach for the treatment of hepatic venous stenosis post major liver resection is safe and efficient to reduce and / or resolve refractory ascites. However, liver function parameters seem not to be improved by the procedure. Stent placement can be a reasonable option in patients with significant residual stenotic disease post angioplasty.

CARD4: In Silico Investigation Of The Effect Of Outflow Graft Narrowing On The Hemodynamics In LVAD Patients

Background: Outflow graft (OG) stenosis is a major complication of LVAD therapy. It causes an increase in the resistance along the OG, leading to pump malfunction and potentially poor clinical outcomes. This study aims at fully characterizing the effect of different degrees of OG stenosis on the hemodynamics. Methods: Computational Fluid Dynamics (CFD) simulations were performed in a patient-derived aortic arch anatomy, with 10- and 14-mm diameter LVAD OG virtually implanted at the aortic root. A stenosis was created just proximal to the anastomosis, with increasing degrees of severity. Simulations performed without stenosis, were considered as reference. Resistance/Capacitance elements were used as outlet boundary conditions. Constant inflow (5 L/min) was applied at the proximal end of the OG. Results: The smallest (25% area reduction) stenosis showed minor changes in pressure gradient and shear stresses for both OG diameters. For a large (~50% area reduction) stenosis, the large size OG showed minor hemodynamic changes, whereas the 10-mm OG resulted in a significant pressure gradient and increased shear stress. All cases with larger than 50% lumen reduction stenosis presented a significant increase in all metrics. The OG stenosis creates a strong jet that enters the aorta and impinges on the contralateral artery wall. This jet results in recirculation areas on the aortic root, specifically adjacent to the closed aortic valve. Conclusion: The effect of stenosis tends to be less severe for the larger size OG. Even though the increase in resistance induced by the stenosis could seem insignificant, the stenosis significantly modifies the hemodynamics. Further study is needed to assess the potential thrombogenicity of OG stenosis and determine the threshold for intervention.

Synergistic effects of vapor and gaseous cavitation and mass-transfer mechanism in a mechanical pump

Dynamic gas–liquid mass-transfer processes are extensively encountered in gas–liquid mixture transport systems, where mechanical pumps pressurize the mixture and are accompanied by flow and mass-transfer instabilities. Herein, our proposed gaseous cavitation model was innovatively developed to revolutionize the independent unidirectional absorbed or evolved mass transfers. Complex gas–liquid behaviors under the synergetic effects of gaseous and vapor cavitations were achieved for the first time in an on-orbit refueling mechanical pump. Four coupled mass-transfer processes, namely, evolution, evaporation, absorption, condensation, and gas–liquid distribution, were investigated through numerical calculations. The results indicated that when the solution was close to critical saturation and conversion of the mass-transfer direction, a surge in the mass-transfer rate, and more intense hydrodynamic instability occurred. The vapor drove the accumulation of the evolved gas along the edge of the vapor in the impeller, where the evolved-dominated mass-transfer bands existed on the suction surfaces of the long blade, exhibiting the degassing characteristics of the vapor cavity, and other regions belonged to absorption-dominated region. Continuous dissolution induced by significant positive pressure gradient led to the maximum absorbed oxygen concentration at the impeller outlet. The maximal increments of absorbed oxygen in the suction chamber, impeller, and volute were 98%, 447%, and 694%, respectively, and the volume fractions were attenuated by 18.3%, 12.5%, and 5.0%, respectively. Notably, an increase in the gas volume fraction was the dominant reason for exacerbating the instability of the impeller forces, and the range of the radial force tended to be narrow and concentrated as the concentration increased.

Cerebral Venous Sinus Pressure and Head Pain: A Case of Cough Headache Secondary to Superior Sagittal Sinus Stenosis (P3-12.009)

<h3>Objective:</h3> Headache triggered by cough is an uncommon disorder that can be primary or secondary in etiology. While the pathophysiology of cough headache is poorly described, there are several theories that suggest that an interplay of elevated intracranial pressure (ICP) and increased central venous pressure results in nociceptor activation with cough. We present a case of secondary cough headache resulting from sagittal sinus stenosis. <h3>Background:</h3> A 31-year old female with a history of migraine presented with a new headache described as 2–5 minute spikes of severe head pain triggered by cough or Valsalva. MRI brain imaging showed a 1.5 cm left para-falcine extra-axial mass involving the lateral wall of the sagittal sinus, most consistent with a meningioma. This finding was initially thought to be unrelated to her head pain. The patient’s head pain remained refractory to typical migraine treatments; however, it responded well to indomethacin and acetazolamide. Due to intolerable side effects, acetazolamide was tapered off and cough-induced head pain recurred. Venous manometry revealed a significant pressure gradient across the sagittal sinus stenosis. Her symptoms significantly improved with meningioma resection and superior sagittal venous stenting. <h3>Design/Methods:</h3> NA <h3>Results:</h3> NA <h3>Conclusions:</h3> This a rare presentation of cough headache secondary to superior sinus stenosis, which significantly improved on correction of increased venous pressure. This case highlights the role of pressure dynamics within the cerebral venous sinus system not only in the etiology of primary and secondary cough and other Valsalva-induced headaches, but also as a potential etiology in patients with idiopathic interracial hypertension with venous sinus stenosis. This case also suggests that venous stenting can be an alternative to acetazolamide. Prompt recognition of secondary causes of cough headache is essential for early intervention. <b>Disclosure:</b> Ms. Haddad has nothing to disclose. Dr. Wang has nothing to disclose. Dr. Parikh has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Biohaven. Dr. Parikh has received personal compensation in the range of $500-$4,999 for serving as a Author with Medlink.