Pressure Gradient Research Articles

Prospective evaluation of patients with non-cirrhotic portal hypertension: A single centre study.

Non-cirrhotic portal hypertension (NCPH) is a spectrum of liver diseases, including porto-sinusoidal vascular disorder, with portal hypertension (PH) in the absence of cirrhosis. The natural history and diagnostic approach to NCPH are not well understood. We aimed to evaluate disease progression and outcomes in NCPH. Patients with or at risk for NCPH were enrolled in a single centre prospective study; two groups were formed based on the presence of specific features of PH, such as varices, collaterals, portal hypertensive gastropathy or portal hypertensive bleeding. All participants underwent a baseline liver biopsy. Liver stiffness measurement (LSM), and imaging were repeated every 6-12 months. Fifteen patients without specific features of PH (Group I), and 35 patients with specific features (Group II) were enrolled. The median follow-up time was 50 months. Group II had higher hepatic venous pressure gradients, non-invasive measures of PH and a lower platelet count (PLT) when compared to Group I. Rates of survival and decompensation were similar in both groups. Patients with PLT ≤100 K/mcL had lower survival compared to those with PLT >100 K/mcL. Patients with LSM ≥10 kPa had lower survival and survival without decompensation when compared to patients with LSM <10 kPa. Patients irrespective of specific features of PH had similar survival or survival without decompensation. Patients without specific features are at risk for disease progression and should be monitored closely. Thrombocytopenia and increased LSM are associated with severe forms of liver disease, which are strongly associated with outcomes.

Improved Hemodynamics with Self-Expanding Compared to Balloon Expandable Transcatheter Aortic Valve Implantation in Small Annulus Patients: A Propensity-Matched Analysis

Patients with small aortic annuli (SAA) pose a challenge in aortic valve replacement patients due to potential for prosthesis-patient mismatch (PPM). The objective of this study was to compare clinical and hemodynamic outcomes of self-expandable valves (SEV) versus balloon-expandable valves (BEV) transcatheter aortic valve implantation (TAVI) in patients with severe aortic stenosis and SAA. All patients who underwent TAVI for severe native aortic stenosis with a SAA between January 2018 and December 2022 were retrospectively included in the study from a single center. Propensity score matching was performed to balance baseline characteristics. Bioprosthesis valve dysfunction (BVD) was based on modified Valve Academic Research Consortium 3 (VARC-3) criteria. A total of 1170 TAVI procedures were performed between 2018 and 2022. After applying the exclusion criteria, 332 patients reported a SAA at CT scan and matching created 109 balanced pairs. Echocardiographic data at discharge showed higher mean transvalvular gradients (p<0.001), higher grades of mitral regurgitation (p=0.029), and lower ejection fraction (p<0.043) in BEV when compared to SEV. At follow-up, significant differences favoring the SEV group regarding BVD were observed (p=0.002), especially in terms of severe PPM (p=0.046), and at least moderate structural valve deterioration (p=0.040). In conclusion, TAVI in patients with SAA using a BEV was associated with lower valve areas, higher mean pressure gradients and PPM (including severe) compared to SEV. Short- and midterm all-cause and cardiac-related mortality did not differ between the two groups. Future randomized studies with extended follow-ups are warranted to validate these outcomes.

Heller Cardiomyotomy in end stage of achalasia with mega esophagus: Results in five cases

Achalasia is a motility disorder of esophagus with poor emptying and, characterised by a lack of peristalsis and impaired relaxation of the lower esophageal sphincter with high LES pressure,diameter of esophsgous can increase, and some patients progress to develop end-stage achalasia as megaesophagus or sigmoid esophagus and significant form dilation and tortuosity.These omplications occurs in between 5% and 20% of patients with acha­lasia. This group of patients if untreated are at risk of aspiration, aspiration pneumonia, and malnutrition. The management of this type of achalasia, aims to palliate symptoms by improving esophagus emptying and reducing the pressure gradient. In this group of patients, pneumatic dilatation (PD), surgical myotomy, or peroral endoscopic myotomy (POEM) may be less or not effective. Esophagectomy for the treatment of end-stage achalasia remains a controversial topic and has been recommended by some authors. We describe 5 patients with end-stage achalasia who was been successfully managed with laparotomy heller cardiomyotomy . In 4,12,18,24 months follow- up the condition of patients was good.

Retrospective evaluation of a right heart parameter score in the assessment of precapillary pulmonary hypertension in dogs (2017-2021): 135 cases.

To determine if emergency and critical care residents can identify moderate to severe precapillary pulmonary hypertension on cardiologist-obtained cineloops using a pulmonary hypertension score (PHS) and report the interobserver variability of the PHS. Multicenter, retrospective, case-control study from 2017 to 2021. Private referral center and veterinary teaching hospital. One hundred and thirty-five client-owned dogs that underwent diagnostic echocardiography. None. Medical records of dogs with stage B1 myxomatous mitral valve disease (MMVD) and dogs diagnosed with precapillary pulmonary hypertension (PCPH) via echocardiograms were reviewed. Dogs were categorized by a cardiologist into 5 groups (normal, B1 MMVD, mild, moderate, and severe PCPH) based on Doppler pulmonary pressure gradients and right heart morphology. Cineloops from each case were subjectively evaluated by emergency and critical care residents for the presence of right atrial and ventricular enlargement, right ventricular hypertrophy, interventricular septal flattening, and pulmonary artery and trunk enlargement to form a composite pulmonary hypertension score out of 8 (PHS8). When available, signs of peritoneal effusion and distention of the caudal vena cava were subjectively assessed to generate a pulmonary hypertension score out of 10 (PHS10). There was excellent discrimination of moderate to severe PCPH versus grouped absent to mild PCPH using PHS8 (area under the receiver operator curve [AUC] [95% confidence interval, CI]=0.90 [0.84-0.95], P<0.0001) and PHS10 (AUC [95% CI]=0.89 [0.81-0.97], P<0.0001). PHS8≥3 was 64% sensitive and 98% specific for moderate to severe PCPH (positive likelihood ratio [LR+] 32, negative likelihood ration [LR-] 0.37). PHS10≥3.3 was 64% sensitive and 92% specific for moderate to severe PCPH (LR+ 8, LR- 0.39). Interobserver agreement was good to excellent (intraclass correlation coefficient [ICC]=0.74 [95% CI: 0.66-0.80], n=135). Residents identified moderate to severe PCPH in dogs using PHS on cineloops previously obtained by a cardiologist. The interrater agreement was good to excellent with limited training. Prospective studies to determine if residents can obtain diagnostic images for PHS are warranted.

Effects of roughness on non-equilibrium turbulent boundary layers

The effects of roughness were considered as part of a NATO Advanced Vehicle Technology effort titled ‘Non-Equilibrium Turbulent Boundary Layers at High Reynolds Numbers’ (NATO AVT-349). This paper comments on the current state of understanding of the flow physics and modelling efforts to predict rough-wall boundary layer behaviour. Outer layer similarity to smooth wall flows and Reynolds number effects are discussed for zero, favourable, and adverse pressure gradients based on the results of experiments and numerical simulations. Various types of modelling are considered including Reynolds averaged Navier-Stokes (RANS) models with different roughness and turbulence models, wall-modelled large eddy simulations (WMLES), and resolvent models. Current needs and gaps in present understanding are discussed along with recommendations for future experiments and computations.

Generalised Couette flow of nanoliquid among two concentric channels with particles injection

In the presence of nanoparticle injection, buoyancy power, constant pressure gradient, variable viscosity coefficient, magnetic field, mass diffusivity of thermophoresis, and Brownian motion, the hydrodynamic nanoliquid conducted with electric current flows through the gap between two concentric cylindrical channels of infinite length. The focus of this article was on generalised Couette flow that is flow in which the outer channel plate moves at a uniform velocity while still being subjected to a pressure gradient. Here we use the RKF45 numerical method and the shooting technique to solve dimensionless momentum, energy, and concentration equations. How the obtained parameters controlled on flow rate, temperature and concentration of the fluid have been investigated and appearances through respective graphs. The high magnitude of nanoliquid flow rate with outer channel wall motion and pressure gradient parameters has been observed. The nanoliquid temperature declines with an annular gap parameter while amplified thermophoresis and magnetic parameter values enrich the fluid temperature. In addition, loftier values of variable viscosity and Brownian motion parameters boost the nanoliquid concentration.

First Successful Wireline Stress Testing in a Gas Hydrate Reservoir in the Hyuganada Sea, Japan

This study presents a stress testing operation conducted using a wireline formation tester in a newly discovered gas hydrate prospect located offshore in Japan. The campaign, which spanned from December 2021 to January 2022, involved drilling a well using logging-while-drilling technology. Subsequently, wireline formation testing and stress testing were successfully conducted at three different depths within a gas hydrate-concentrated zone. The testing was accomplished in a single riserless descent, with the primary goal of obtaining crucial data such as mobility, formation pressure, and fracture gradient for one of the prospects. This operation marked the first stress testing job performed with dual packers in an open water and deepwater environment specifically for gas hydrate reservoirs. The study also provides a comprehensive interpretation of the data gathered during the operation. Moreover, it evaluates various properties such as formation mobility, formation pressure, initial breakdown pressure, closure pressure, fracture propagation pressure, and instantaneous shut-in pressure.

Multifaceted simulation: Finite volume and finite element modeling of blood flow in multiple stenosed arteries

Cardiovascular illnesses are a primary global health concern because they are frequently brought on by arterial stenosis. The complicated hemodynamics of blood flow via elliptically shaped arteries with numerous stenotic lesions along their top and bottom walls are examined in this paper. Carreau fluid model is used with Navier–Stokes equations in this study. The complete comparative study is done by using the Finite Element and Finite Volume Methods. This study uses commercial software to examine blood flow velocity, pressure and temperature distributions under various physiological situations at Reynolds number 30. Our results illuminate the interaction between flow dynamics, stenosis characteristics, and arterial geometry. The novelty of the work is to investigate how stenosis size, shape, and location affect pressure gradients, and flow disturbances. These observations provide helpful direction for understanding disease progression, designing treatments, and possibly new stent designs. The future direction of this research may involve further exploration of the interplay between hemodynamics and arterial stenosis by incorporating advanced computational models. Additionally, studies focusing on in vivo validation and clinical applications could enhance the translational impact of the findings. Collaborations between researchers, clinicians, and engineers may pave the way for personalized treatment strategies and innovations in cardiovascular care based on a deeper understanding of the intricate dynamics within diseased arteries.

Optimizing pressure gradient on the MHD peristaltic blood flow of nanofluids by - response surface methodology

This study focuses on optimization of pressure gradient on MHD peristaltic nanofluid flow by response surface methodology (RSM). The governing equations, including continuity, motion, nanoparticle, and concentration force are solved by disregarding inertial forces and employing the approximation of long-wavelength. The perturbation method is used to solve the resultant nonlinear coupled partial differential equation analytically. Mathematical and graphical outputs for concentration, temperature, and pressure rise, considering all physical parameters, are presented. Numerical computation is applied to assess expressions for friction forces and pressure rise. Magnetohydrodynamics has various applications in various microchannel designs for efficacious flow control in pumping fluids for both pulsating and non-pulsating continuous flow. Finally, Response Surface Methodology (RSM) is used for performing sensitivity analysis and its optimization. ANOVA tables are generated with the help of MINITAB-19 which is a statistical software. The sensitivity results are displayed in tabular and graphical form and concluded that M is more sensitive than other input parameters for ΔPat the low level and the input parameter Nt is most sensitive among others at middle and high levels. Further, Temperature and pressure of the flow has different responses for various values of magnetic, thermophoresis and Brownian motion parameter.

Оценка чувствительности методов диагностики в выявлении гемодинамически значимых односторонних стенозов почечных артерий

Objective. Assessment of renal artery stenosis significance in patients with resistant arterial hypertension using non-invasive diagnostic methods and to compare them with the results of selective angiography and methods of physiological assessment of renal artery stenoses.Materials and methods. Prospectively, 156 patients with drug-resistant arterial hypertension and signs of renal artery stenosis detected by doppler ultrasonography of renal arteries were included in the study. Subsequently, 25 patients were excluded from the study due to multiple variant renal blood supply and bilateral renal artery stenosis. The remaining patients (n=131) underwent selective angiography of renal arteries, and 66 of them additionally underwent CTA of renal arteries with intravenous contrast. If the artery narrowing was 90% or more (n=27) in diameter, the stenosis was considered hemodynamically significant and further stenting of the affected artery was performed, and in case of 60-90% stenosis (n=52) additional assessment of functional significance of the stenosis was performed by measuring translesional pressure gradient, fractional blood flow reserve, instantaneous blood flow reserve (iFR) and Pd/ Pa ratio. Results. Among all patients (n=131), in whom the doppler ultrasonography of renal arteries showed signs of unilateral renal artery stenosis, after angiography combined with additional methods of functional significance assessment, hemodynamically significant renal artery stenosis was confirmed in 41% of cases (n=54). Thus, the sensitivity of doppler ultrasonography of renal arteries in detection of hemodynamically significant stenoses was 74%, prognostic value of positive 78% and negative result 64% (p&lt;0,001). According to CTA (n=66) renal artery stenosis was confirmed in 56 patients. The results of CTA of renal arteries in 88% of cases coincided with the results of selective angiography, and using additional functional methods hemodynamically significant stenosis was confirmed in 32 (48%) patients. The sensitivity of CTA in detection of hemodynamically significant stenoses of renal arteries was 69%, specificity 91%, prognostic value of positive and negative results was 91 and 68% respectively. According to selective angiography, out of 131 patients, 24 patients had no renal artery stenosis, 28 patients had stenosis &lt;60%, 27 patients had renal artery stenosis &gt;90% and 52 patients had stenosis 60-90%. Patients with stenosis &lt;60% were not considered candidates for renal artery stenting.

Wearable self-powered ballistic signal detectors with ferroelectric composites arrays for cardiovascular and diabetic complication

Abstract Background Flexible and wearable electronic devices with lightweight are needed to monitor and guide treatment in patients with cardiovascular disease and diabetic complication. We aimed to develop self-powered wearable bio-signal sensing arrays for cardiovascular and diabetic complication diagnosis and continuous monitoring. Methods Ferroelectric composites were designed to have piezoelectric property and high flexibility. Detection of arterial pulse as ballistogram (BCG) was simultaneously compared with electrocardiogram (ECG) in 20 controls. Heart rate and components of ECG was compared with those of BCG. Then, 9 ferroelectric BCG sensors as a square type array with self-power generation were fabricated to attachable thin film. Pressure distribution with BCG sensor array attached to socks were compared between 20 controls and 20 patients with diabetic neuropathy or vasculopathy during standing and ambulation for gait pressure distribution. Pressure distribution pattern was compared to neuropathy and vasculopathy parameters. Results Heart rate between BCG and ECG was significantly correlated (interclass correlation coefficient, ICC 0.99, 95% CI 0.98-0.99, p&amp;lt;0.001). QRS and T wave in ECG were correlated to second and third wave in BCG. Radial artery augmentation index by blood pressure monitoring was significantly correlated to BCG pressure (ICC 0.76, 95% CI 0.38-0.90, p=0.002). Analysis of foot pressure distribution demonstrated the highest pressure point at the anterolateral plantar area below a little tow. However, pressure gradient between anterolateral and anteromedial plantar area in diabetic patients was greater than that in controls (42.3±10.2 mV vs. 31.2±8.5 mV, p=0.024). Pressure gradient in diabetic patients was correlated to ankle-brachial index (ICC 0.62, 95% CI 0.32-0.90, p=0.036), but not to neuropathy parameters. Conclusion Wearable BCG sensor could accurately detect heart rate, blood pressure index and significantly correlated to ABI. Pressure distribution pattern and gradient analysis in diabetic patients by wearable BCG sensor arrays might predict diabetic complications. Gait remedial training guided by wearable BCG sensor arrays might aid to prevent diabetic complications.

DISEASED BILE FLOW UNDER THE EFFECTS OF HEAT TRANSFER AND CHEMICAL REACTIONS

The movement of bile inside ducts in a diseased state is investigated using a mathematical model that takes into account heat transport and chemical interactions. Bile is considered as a viscous fluid, geometry of ducts is assumed as finite length asymmetric channel and the flow is induced by peristaltic wave along the length of channel walls. Under the presumption of a long wave length and a low Reynolds number, the formulas for axial velocity, pressure gradient, volume flow rate, stream function, pressure increase, shear stress, and heat transfer coefficient are produced. In the end, a plot and discussion are made of how different emergent factors affect the relevant physical quantities.

Bionic noise reduction design of axial fan impeller

Abstract Fans are integral equipment widely employed in both industrial settings and daily life. However, a persistent challenge in their design lies in the inherent conflict between aerodynamic performance and noise levels. Improving aerodynamic efficiency often results in a compromise of acoustic performance. To tackle this issue, we employed the bionic design method to craft a novel axial fan impeller featuring a bionic curved hub and bionic serrated leading edges. The impact of structural optimization on the aerodynamic and acoustic properties of the impeller, as well as the influence of optimization parameters on these properties, were systematically investigated through numerical simulations. The bionic impeller was then fabricated using 3D printing, and its aerodynamic and noise performance were experimentally evaluated by integrating it into an external air conditioner. Comparison of the flow field and sound field data between the optimized and prototype impellers revealed noteworthy outcomes. The curved wall at the bionic hub's tail effectively diminished the pressure gradient on the hub surface, directing the airflow toward the rear end of the hub. This design enhancement significantly reduced the turbulent area behind the prototype impeller's hub. Additionally, the bionic serrated structure, when appropriately designed, demonstrated its efficacy in reducing the contact area between the blade's leading edge and incoming flow. This led to the dispersion of stress concentrations and the inhibition of strong turbulence generation. Notably, the experimental results indicated a 3.7% increase in air volume flow rate and a 2.3dB reduction in noise for the optimized impeller compared to the prototype. This successful mitigation of the trade-off between aerodynamic performance and noise level underscores the effectiveness of our bionic design approach.&amp;#xD;

Influence of Runner Downstream Structure on the Flow Field in the Draft Tube of a Small-Sized Water Turbine

The flow in the draft tube of the water turbine is affected by the upstream flow and the inherent structure accompanied by various undesirable characteristics, affecting the efficient and stable operation of the water turbine. Changing the flow structure downstream of the runner is an important measure to reduce hydraulic loss in the draft tube and improve stability. In this study, three downstream structures of the runner, namely, the non-locking nut, small locking nut, and extended locking nut are numerically calculated and verified using experimental results. The unstable flow characteristics of the draft tube are analyzed using variations in swirling flow, backflow, pressure gradient, and vortex strip. The results show the non-negligible effect of the locking nut, which significantly reduces the rotational momentum flux at the draft tube inlet, accelerates the decay rate of the swirling flow, and suppresses the generation of axial low pressure. The small locking nut significantly reduces the pressure gradient, shortens the backflow zone, and decreases the backflow velocity. The extended locking nut reduces the backflow zone in some sections and reduces the vortex zone of the straight section but prolongs the backflow zone and increases the backflow velocity.

#282 Correction of portal hypertension and renal dysfunction with losartan in patients with liver cirrhosis

Abstract Background and Aims To increase the effectiveness of drug correction of portal hypertension, taking into account the functional state of patients with liver cirrhosis, using Angiotensin receptor blockers (ARBs) Method The work summarizes the results of an examination of 35 patients with liver cirrhosis (LC) who were treated in the hepatology department. The patients were divided into two subgroups: the first consisted of 21 patients with liver cirrhosis without ascites, Child-Pugh class A, and the second subgroup included 14 patients with liver cirrhosis with ascites, Child-Pugh class B. We evaluated the effect of the orally active angiotensin II receptor antagonist, losartan, on portal pressure in patients with cirrhosis and portal hypertension. Patients with (hepatic venous pressure gradient [HVPG] ≥ 13 mmHg) portal hypertension at baseline measurement were treated with an oral dose of 25 mg losartan once daily for 1 week. Results The examined patients were analyzed for the functional state of the kidneys and its relationships with the main parameters of portal hypertension and hepatic cellular failure. Comparative characteristics of the main indicators of renal function revealed significant differences in functional parameters depending on the degree of hepatic cellular failure. In the group of patients with cirrhosis with ascites, there was a significant decrease in renal GFR to 77.5 ± 1.4 ml/min, in contrast to the unchanged level of GFR in the group of patients with cirrhosis without ascites - 99.3 ml/min. However, no significant changes in serum creatinine levels were detected. Therapy with Losartan in patients with Child-Pugh class A liver cirrhosis at a dose of 25 mg/day reduces PV pressure gradient by 18.1%, at a dose of 12.5 mg/day does not significantly affect the level of portal hypertension, but improves the functional state of the kidneys (increases FPR by 56%, EPP by 17.3%). Conclusion The present study indicates that angiotensin II blockade with orally administered losartan is safe and highly effective in the treatment of portal hypertension. In patients with liver cirrhosis with the development of impaired renal reabsorption function and a decrease in FPR from 10% to 8% in the treatment of portal hypertension, the drug of choice is an ARBs (losartan 25 mg/day) with blood pressure &amp;gt; 115/60 mmHg.

Impact of Low Freestream Turbulence and Surface Roughness on the Flat-Plate Boundary Layer Transition Under a High-Lift Airfoil Pressure Gradient

Abstract Effects of low incoming freestream turbulence level (Tu &amp;lt; 1%) and surface roughness on the transition of flat-plate boundary layers under a high-lift airfoil pressure gradient have been investigated. Time-resolved streamwise and wall-normal velocity fields with surface roughness values of Ra/C = 0.065 × 10−5, 4.417 × 10−5, and 7.428 × 10−5 have been measured at a fixed Reynolds number of 5.2 × 105 and freestream turbulence intensity of 0.2%. For the reference smooth surface of Ra/C = 0.065 × 10−5, a laminar separation bubble forms from about 64% to 83% of the chord length. Increasing surface roughness has little impact on the laminar boundary layer separation onset but reduces the height and length of the separation bubble and induces earlier transition. For Ra/C = 4.417 × 10−5, displacement thickness during transition is slightly thinner and the overall momentum deficit is slightly lower than those for Ra/C = 0.065 × 10−5. For Ra/C = 7.428 × 10−5, the separation bubble becomes hardly visible as the transition mode approaches the attached mode, and turbulent mixing by the wall-bounded turbulence becomes dominant. In addition, the portion of turbulent wetted area increases due to earlier transition, and momentum deficit increases more rapidly in the turbulent wetted area. Thus, the overall momentum deficit for Ra/C = 7.428 × 10−5 is larger than that for Ra/C = 0.065 × 10−5.

#1397 Predictive factors for bioprosthetic valve stenosis and prognostic factors for survival following TAVR in hemodialysis patients with severe AS

Abstract Background and Aims Transcatheter aortic valve replacement (TAVR) is a promising option for the treatment of severe aortic valve stenosis (AS) in patients undergoing hemodialysis. Although the incidence of bioprosthetic valve deterioration (SVD) after TAVR has been reported to be lower than after surgical aortic valve replacement (SAVR), hemodialysis itself is still associated with a high risk of SVD. Until now, the factors that determine the prognosis of TAVR in hemodialysis patients were unknown. We previously reported that preoperative hypomagnesemia was correlated with an increase in postoperative mean aortic valve pressure gradient (MPG), an index of bioprosthetic valve stenosis as one of the indicators of SVD, in hemodialysis patients (Ren Fail. 2022 Dec;44(1):1083-1089). However, the study had a limited sample size of 24 cases, which raised concerns about statistical power. Therefore, we re-evaluate predictors of SVD and life expectancy in a larger number of post-TAVR hemodialysis patients. Methods From April 2012 to November 2021, all 100 hemodialysis patients treated with TAVR at Osaka University Hospital were included in the analysis. Pre- and post-operative demographic and laboratory data were analyzed by linear mixed-effects model and cox proportional hazards model. Results During the follow-up period (maximum 7 years), 4 out of 100 patients required re-TAVR (valve-in-valve) due to valve stenosis. The MPG increased over time with the lower preoperative serum Mg concentration (linear mixed-effects mode; +1.40 mmHg/year per 1mg/dl lower in Mg, p=0.006). However, serum calcium, phosphate, and intact PTH levels had no significant effect on the increase in MPG. In addition, a higher preoperative left ventricular ejection fraction (LVEF) was associated with a lower risk of death in a multivariate Cox proportional hazards model (hazard ratio [HR] 0.97 per 1% increase in LVEF; P=0.02). Conclusions Consistent with our previous report, preoperative hypomagnesemia was associated with increased MPG after TAVR. In addition, preoperative low cardiac function (LVEF&amp;lt;40%) may be a risk factor for postoperative mortality in dialysis patients. This was a single-center observational study, and the number of patients was still small, so our data may not be necessarily applicable to every patient. Further research is needed to identify a prognostic predictor of SVD and mortality, that will lead to the prevention of adverse outcomes in hemodialysis patients.

#780 “In vivo” difference in ultrafiltration coefficient between two same membrane dialyzers: bigger surface area accounts for better dialysis outcomes?

Abstract Background and Aims Ultrafiltration coefficient (KUF) is a measure of dialyzer permeability to water, given by manufacturers, and expressed in milliliters/hour/mmHg of pressure gradient. Most dialyzers used at this moment are classified as high-flow as having a KUF &amp;gt;20 mL/h/mmHg. KUF value of a dialyzer is an “in vitro” measure which does not correlate with “in vivo” measure, stated to be 5-30% less than theoretical KUF. According to this statement, we wanted to study differences between theoretical and real KUF of two dialyzers with the same membrane composition and different surface area. For this task, we chose 2 dialyzers of usual use in our dialysis unit: FX CorDiax 1000 and FX CorDiax 80 (®FMC). These dialyzers have a main difference in Surface area: 2.3 and 1.8 m2, respectively, and have a theoretical KUF of 76 and 64 mL/h/mmHg. Also, both dialyzers differ in intern diameter (210 vs 185 µm). Method A prospective, not randomized trial was conducted. Inclusion criteria were patients in chronic dialysis at our center, in postdilutional online hemodiafiltration with a FX1000 dialyzer. All patients were informed and accepted freely signing an informed consentment. On 2 consecutive weeks, the intermediate dialysis session of the week was performed in a DBB-EXA dialysis monitor (®Nikkiso), first with a FX CorDiax 1000 and next week with a FX CorDiax 80, with habitual patient dialysis parameters (240 minutes). Blood tests were taken previous and after the session to evaluate clearance differences between both filters. During the session, pressure and flow data was recorded, with an “in vivo” KUF measurement given by the monitor. Results Dialysis sessions were performed in 12 patients who met inclusion criteria. Data results are shown in Table 1. Significant differences between FX CorDiax 1000 and FX CorDiax 80 were observed in prefilter pressure (p 0.008), convective volume (p 0.034), prolactin reduction ratio (p 0.012), “in vivo” KUF/ “in vitro” KUF ratio (p 0.002). “In vivo” KUF graphic given by the monitor showed a logarithmic function curve, with a stabilization between the 2nd and 3rd hour of the session. Conclusion In our study, measurement of “in vivo” KUF by Nikkiso monitor showed a slow decrease after 2nd hour of session, probably related with protein cake of membrane pores. “In vivo” KUF measure was approximately a 40-45% of theoretical value given by manufacturer. The “in vivo” KUF/ “in vitro” KUF ratio was higher for the smaller dialyzer, which probably means a higher optimization of its surface area with usual dialysis sessions. Convective volume and prolactin reduction ratio, as parameters of dialysis efficacy, are higher in the dialyzer with higher surface area and inner intern diameter.

Formation of eastern boundary undercurrents via mesoscale eddy rectification

Abstract Eastern Boundary Upwelling Systems (EBUSs) host equatorward wind-driven near-surface currents overlying poleward subsurface undercurrents. Various previous theories for these undercurrents have emphasized the role of poleward alongshore pressure gradient forces (APF). Energetic mesoscale variability may also serve to accelerate undercurrents via mesoscale stirring of the potential vorticity gradient imposed by the continental slope. However, it remains unclear whether this eddy rectification mechanism contributes substantially to driving poleward undercurrents in EBUS. This study isolates the influence of eddy rectification on undercurrents via a suite of idealized simulations forced either by alongshore winds, with or without an APF, or by randomly-generated mesoscale eddies. It is found that the simulations develop undercurrents with strengths comparable to those found in nature in both wind-forced and randomly forced experiments. Analysis of the momentum budget reveals that the along-isobath undercurrent flow is accelerated by isopycnal advective eddy momentum fluxes and the APF, and retarded by frictional drag. The undercurrent acceleration may manifest as eddy momentum fluxes or as topographic form stress depending on the coordinate system used to compute the momentum budget, which reconciles these findings with previous work that linked eddy acceleration of the undercurrent to topographic form stress. The leading-order momentum balance motivates a scaling for the strength of the undercurrent that explains most of the variance across the simulations. These findings indicate that eddy rectification is of comparable importance to the APF in driving poleward undercurrents in EBUSs, and motivate further work to diagnose this effect in high-resolution models and observations, and to parameterize it in coarse-resolution ocean/climate models.

Total bile acids levels as a stratification tool for screening portopulmonary hypertension in patients with decompensated cirrhosis.

Echocardiography is necessary for portopulmonary hypertension diagnosis, and identifying patients with cirrhosis who require it is challenging. In this study, we aimed to investigate the utility of the total bile acid (TBA) levels as a screening tool for identifying patients with decompensated cirrhosis who should undergo echocardiography for portopulmonary hypertension diagnosis. We evaluated 135 patients with decompensated cirrhosis who underwent liver transplantation. Subsequently, factors contributing to tricuspid regurgitation pressure gradient (TRPG) elevation (≥30mmHg) were analyzed using preoperative data, including the TBA levels. The median age of patients was 58years (61 women), and 45 and 90 patients had Child-Turcotte-Pugh grades of B and C, respectively. The median TRPG level was 21mmHg, and 17 patients (12.6%) showed TRPG elevation. Multiple logistic regression analysis revealed that elevated TBA (odds ratio 4.322; p=0.013) and main pulmonary artery diameter ≥33mm (odds ratio 4.333; p=0.016) were significantly associated with TRPG elevation. The TBA cut-off value (167.7μmol/L) showed a high diagnostic performance, with 70.6% sensitivity and 64.4% specificity. Ursodeoxycholic acid (UDCA) administration increased the TBA levels dose-dependently. Analysis stratified by UDCA use revealed that in patients not taking UDCA (n=59), elevated TBA levels and younger age significantly contributed to TRPG elevation. However, in those taking UDCA (n=76), this contribution disappeared, suggesting that UDCA consumption reduced TBA levels' efficiency in diagnosing TRPG elevation. The TBA levels may be a potential screening tool for TRPG elevation; however, caution is warranted when interpreting cases treated with UDCA.