Estimation Of Capillary Pressure Research Articles

Unveiling the Role of PTFE Surface Coverage on Controlling Gas Diffusion Layer Water Content.

Gas diffusion layers (GDLs) are usually coated with a hydrophobic agent to achieve a delicate balance between liquid and gas phases to maximize mass transport. Yet, most GDL numerical models to date have assumed an average contact angle for all materials, thereby eliminating the possibility of studying the role of the polytetrafluoroethylene (PTFE) content. This study introduces two mixed wettability algorithms to predict the mixed wetting behavior of GDLs composed of multiple materials. The algorithms employ contact angle and distance to solid materials to determine the critical capillary pressure for each pore voxel. The application of the algorithms to the estimation of capillary pressure vs saturation curves for two GDLs, namely, a micro-computed tomography (μ-CT) reconstructed SGL 39BA GDL and a stochastically reconstructed Toray 120C GDL, showed that, in agreement with experimental data, the addition of PTFE resulted in a decrease in saturation at a given capillary pressure. For Toray-120C, the mixed wettability model was capable of reproducing experimentally observed features in the intrusion curve at low saturation that could not be reproduced with a single wettability model, providing a clear link between PTFE coverage and intrusion at low saturation. Numerical results also predicted an increased breakthrough pressure and a decrease in saturation with increasing PTFE, in agreement with experimental observations. The decreased saturation at breakthrough improves gas transport through the layer while maintaining the layer's ability to remove water. Diffusivity simulations confirm the increase in diffusivity at breakthrough with increasing PTFE, thereby providing a rationale for the addition of PTFE, as well as for the optimal amount. This study emphasizes the importance of multimaterial wetting models and calls for more detailed investigations into PTFE and ionomer distributions in GDLs and catalyst layers, respectively.

CO2 storage: threshold capillary pressure estimate in a remoulded caprock specimen

CO2 storage: threshold capillary pressure estimate in a remoulded caprock specimen

A Method to Correct Steady-State Relative Permeability Measurements for Inhomogeneous Saturation Profiles in One-Dimensional Flow

AbstractTraditionally, steady-state relative permeability is calculated from measurements on small rock samples using Darcy’s law and assuming a homogenous saturation profile and constant capillary pressure. However, these assumptions are rarely correct as local inhomogeneities exist; furthermore, the wetting phase tends to be retained at the outlet–the so-called capillary end effect. We have introduced a new method that corrects the relative permeabilities, analytically, for an inhomogeneous saturation profile along the flow direction. The only data required are the measured pressure drops for different fractional flow values, an estimate of capillary pressure, and the saturation profiles. An optimization routine is applied to find the range of relative permeability values consistent with the uncertainty in the measured pressure. Assuming a homogenous saturation profile systematically underestimates the relative permeability and this effect is most marked for media where one of the phases is strongly wetting with a noticeable capillary end effect. Relative permeabilities from seven two-phase flow experiments in centimetre-scale samples with different wettability were corrected while reconciling some hitherto apparently contradictory results. We reproduce relative permeabilities of water-wet Bentheimer sandstone that are closer to other measurements in the literature on larger samples than the original analysis. Furthermore, we find that the water relative permeability during waterflooding a carbonate sample with a wide range of pore sizes can be high, due to good connectivity through the microporosity. For mixed-wet media with lower capillary pressure and less variable saturation profiles, the corrections are less significant.

A novel approach for estimating pore size distribution and capillary pressure in hydrocarbon zone through hydraulic flow unit framework using NMR log

Nuclear magnetic resonance (NMR) logging imparts a wealth of information regarding the petrophysical characterization of rocks including pore size distribution and capillary pressure. However, the NMR data can only be comprehensively utilized when formation pores are fully water-saturated. As with hydrocarbon saturation increase in rock pores the NMR's transverse relaxation curve (T2 distribution) gets distorted and this in turn causes flawed measurement of petrophysical and fluid properties. Therefore, the estimation of representative pore structure and capillary pressure from hydrocarbon zone utilizing T2 distribution has traditionally been quite arduous. The previous correction methods in this regard mostly require expensive core data for their implementation, which makes them less desirable. In this study, a novel workflow has been introduced which does not necessitate expensive core data for its application. The new method employs the concept of hydraulic flow units (HFUs), which are zones within a reservoir having consistent petrophysical and geological properties to subdivide the reservoir rock while investigating the T2 distribution character variation through a statistical approach to determine the most optimally informed reconstruction of effected T2 distributions in hydrocarbon zone for accurate petrophysical characterization. After implementing the novel workflow on a carbonate reservoir having gas, the before and after comparative analysis of T2 distribution, pore size distribution (PSD) and capillary pressure curves show promising results. The novel workflow establishes a robust and cost-effective methodology for NMR T2 distribution correction in hydrocarbon zone for un-cored and partially cored wells.

Correct estimation of permeability using experiment and simulation

Estimation of permeability of porous media dates back to Henry Darcy [H. Darcy, Les Fontaines Publiques de la Ville de Dijon (Victor Dalmont, 1856)], and its knowledge is essential in many scientific and engineering endeavors. Despite apparent simplicity of permeability measurements, the literature data are scattered, and this scatter not always can be attributed to the precision of experiment or simulation or to sample variability. Here, we demonstrate an excellent agreement (<1%) between experiments and simulations, where experimental results are extensive and stable, while flow is simulated from first principles, directly on three-dimensional images of the sample, and without fitting parameters. Analyzing when experiments and simulations agree reveals a major flaw affecting many experimental measurements with the out-of-sample placement of pressure ports, including industry standards. The flaw originates from (1) incorrect calculation of the applied pressure gradient, (2) omitting virtual part of the measured system, and (3) pressure loss at the sample–tube contact. Contrary to common wisdom, the relative magnitude of (3) is defined by the sample–tube diameter ratio and is independent of the size of sample pores. Our findings are applicable to a wide range of permeability measurements, including geological-sample-type (Hassler cell) and membrane-type. The reported pressure loss (3) also affects two-phase flow measurements, such as capillary pressure estimation. Removing or taking the flaw into account advances the understanding and control of flow-related processes in complex geometries.

A novel echocardiographic estimate of pulmonary vascular resistance employing the hydraulic analogy to Ohm's law.

Assessment of pulmonary vascular resistance (PVR) is critical for accurate diagnosis and optimal pharmacotherapy in pulmonary hypertension. We aimed to test the diagnostic performance of a novel, Doppler-based method to evaluate PVR based on Ohm's law (PVRecho) using pragmatic estimates of pulmonary capillary wedge pressure (PCWP). Simultaneous right heart catheterization (RHC) and echocardiography was performed in a derivation cohort of 111 patients in sinus rhythm referred for PH evaluation and PVRecho independently validated in 238 patients. PVRecho was calculated using pulmonary artery mean pressure estimates (PAMPecho) obtained from peak tricuspid gradient employing a fixed right atrial pressure estimate, PCWPecho was estimated as 10 or 20mmHg using age-related mitral E/A cut-offs and cardiac output from left ventricular outflow. In the derivation cohort, both PAMPecho and PCWPecho estimates demonstrated excellent agreement with catheterization measurements. PVRecho was highly feasible, demonstrated negligible bias and excellent agreement with PVRRHC (Bias=-0.58, SD 2.2mmHg) and outperformed the Abbas method to identify PVRRHC>3WU (AUC=0.85 vs. 0.70; p=0.02). In the validation cohort, PVRecho preserved good invasive agreement with negligible bias, displayed strong diagnostic performance (AUC=0.84) and significant ability to distinguish isolated post-capillary from combined post- and pre-capillary pulmonary hypertension (PH) subgroups (AUC=0.77). PVRecho based on Ohm's law employing pragmatic estimates of PCWPecho demonstrates excellent agreement with invasive reference standard measurements and strong diagnostic ability to identify elevated PVRRHC. This novel approach may be useful during therapy selection to distinguish PH hemodynamic subgroups.

Modified Johnson–Bossler–Naumann method to incorporate capillary pressure boundary conditions in drainage relative permeability estimation

A proposed modification of the Johnson–Bossler–Naumann (JBN) method incorporates capillary pressure at the inlet and outlet of a rock sample. The experimental runs are performed on Berea and Obernkriechner sandstone rock samples. Fluid is injected into Berea rock at capillary to viscous ratios 0.05, 0.1, 0.5, and 1 and into Obernkriechner rock at capillary to viscous ratios 0.05 and 0.25. Rock samples are initially saturated with 20 g/l NaCl water. The experimental observations are analyzed using classical JBN and our modified JBN. The latter's relative permeability curves are found to closely match those derived by applying history matching to a numerical model. This indicates that modified JBN can be used to provide an initial guess for history matching. We also show that accurate estimates of threshold capillary pressure are crucial to obtaining accurate oil relative permeability estimates. In contrast to those derived from the JBN method, modified JBN relative permeabilities are independent of capillary to viscous ratio or injection rate. • The proposed model incorporates capillary pressure at the inlet and outlet boundary. • Experiments are performed to validate the model. • Derived relative permeability curves are less sensitive to capillary number compared to classical methods.

Capillary pressure contribution in fabrics as a function of fibre volume fraction for Liquid Composite Moulding processes

Liquid Composite Moulding processes are considered as promising and effective to manufacture structure composite parts reinforced with synthetic and natural fabrics. The main novelty of this work is the estimation of capillary pressure (Pcap) for both fabrics at different fibre volume fractions (Vf) and with different liquids. From the previous works, the Pcap was defined as the equivalence between Washburn’s equation and Darcy’s law while our novel model for the capillary wicking could predict very well the swelling behaviour of natural fabrics. The combination of our Pcap definition and our novel model was explored in this study. Linear trends, thresholds and extremums of Pcap at different conditions were found for the first time. These results are relevant to estimate the importance of capillary effects during Liquid Composite Moulding processes and extremely valuable for numerical models at the fibrous scale to predict voids formation.

Machine Learning for Capillary Pressure Estimation

Summary Capillary pressure plays an essential role in controlling multiphase flow in porous media and is often difficult to be estimated at subsurface conditions. The Leverett capillary pressure function J provides a convenient tool to address this shortcoming; however, its performance remains poor where there is a large scatter in the scaled data. Our aim, therefore, was to reduce the gaps between J curves and to develop a method that allows accurate scaling of capillary pressure. We developed two mathematical expressions based on permeability and porosity values of 214 rock samples taken from North America and the Middle East. Using the values as grouping features, we used pattern-recognition algorithms in machine learning to cluster the original data into different groups. In each wetting phase saturation, we were able to quantify the gaps between the J curves by determining the ratio of the maximum J to the minimum J. Graphical maps were developed to identify the corresponding group for a new rock sample after which the capillary pressure is estimated using the average J curve of the identified group and the permeability and porosity values of the rock sample. This method also provides better performance than the flow zone indicator (FZI) approach. The proposed technique was validated on six rock types and has successfully generated average capillary pressure curves that capture the trends and values of the experimentally measured data by mercury injection. Moreover, the proposed methodology in this study provides an advanced and a machine-learning-oriented approach for rock typing. In this paper, we provide a reliable and easy-to-use method for capillary pressure estimation in the absence of experimentally measured data by mercury injection.

A novel technique to estimate water saturation and capillary pressure of foam in model fractures

Foam is applied in enhanced oil recovery to improve the sweep of injected gas and increase oil recovery, by greatly reducing the mobility of gas. In the laboratory, X-ray computed tomography is commonly used to evaluate the performance of foam in core plugs. However, foam properties, such as bubble size and capillary pressure, are much more difficult to measure. In recent years, microfluidic models have gained much attention because they easily facilitate the imaging study of in-situ foam. However, it is still challenging to estimate capillary pressure, in a model with a uniform depth of etching. In this paper, we report a novel technique to estimate water saturation and capillary pressure of foam in two 1-meter-long model fractures. Both model fractures are made of glass plates. They have different roughness and hydraulic apertures. Unlike microfluidics with uniform depth of etching, our model fractures each has a variation of aperture. We characterize the roughness and represent the aperture distribution of the fracture as a network of pore bodies and pore throats. In this study, foam is pre-generated and then injected into the fractures. The inlet and outlet valves are closed for 24 hr after foam reaches steady-state. We use a high-speed camera to visualize foam in the fractures. We use ImageJ software to analyze foam texture and quantify bubble density, average bubble size and polydispersivity. In addition, we estimate water saturation and capillary pressure by analyzing images in terms of fracture geometry. We found that water in foam resides in locations of narrow aperture, Plateau borders, lamellae between bubbles, and water films on glass walls. Water-filled zones of narrow aperture and Plateau borders account for almost all the water. During the re-distribution of water and gas in static foam, in-flow and out-flow of water must take paths along the network of Plateau borders and water-occupied zones, as they are the only continuous paths for water flow. In both model fractures, the decrease in water saturation coincides with an increase in capillary pressure, as expected. This novel technique of estimation of water saturation and capillary pressure of foam provides insights for studies of foam in naturally fractured reservoirs with complex geometry, where measuring such foam properties is challenging. This analysis is possible because aperture varies along our model fractures, unlike most microfluidic devices. Our technique would also have an application to foam aquifer remediation and CO2 sequestration.

Left Atrial Expansion Index for Noninvasive Estimation of Pulmonary Capillary Wedge Pressure: A Cardiac Catheterization Validation Study

Pulmonary capillary wedge pressure (PCWP) plays a pivotal role in cardiac disease diagnosis and management. Right heart catheterization (RHC) invasively provides accurate PCWP measurement, but it is impractical for widespread use in all patients. The left atrial expansion index (LAEI), measured on transthoracic echocardiography, describes the relative left atrial volume increase during the left atrial reservoir phase. The aim of this study was to validate LAEI as a noninvasive parameter for PCWP estimation. A total of 649 chronic cardiac patients (mean age, 66±14years; mean PCWP, 14±7.6mm Hg; mean left ventricular ejection fraction, 50±15%) who underwent both clinically indicated RHC and transthoracic echocardiography within 24hours were retrospectively enrolled. Patients were randomly divided into derivation (n=509) and validation (n=140) cohorts. PCWP was measured during RHC and defined as elevated when >12mm Hg. Transthoracic echocardiographic parameters and LAEI were measured offline, blinded to RHC results. In the derivation cohort, LAEI correlated logarithmically with PCWP, and the log-transformed LAEI (lnLAEI) correlated linearly with PCWP (r=-0.73, P<.001). lnLAEI showed an independent and additive predictive role for PCWP estimation over clinical and diastolic dysfunction (DD) parameters. The diagnostic accuracy of lnLAEI for elevated PCWP identification (area under the curve=0.875, P<.001; optimal lnLAEI cutoff<4.02) was higher than either the single DD parameters or their combination. In the validation cohort, lnLAEI cutoff < 4.02 showed higher accuracy than the 2016 DD algorithm (88% vs 74%) for elevated PCWP identification. Finally, the equation PCWP=38.3 - 6.2×lnLAEI, obtained from the derivation cohort, predicted invasively measured PCWP in the validation cohort. In a cohort of patients with various chronic cardiac diseases, lnLAEI performed better than DD parameters and the 2016 DD algorithm for PCWP estimation. lnLAEI might be a useful echocardiographic parameter for noninvasive PCWP estimation.

Added value of left atrial expansion index for non-invasive estimation of pulmonary capillary wedge pressure

Abstract Introduction Right heart catheterization (RHC) is the reference technique for pulmonary capillary wedge pressure (PCWP) measurement but remains invasive. Transthoracic echocardiography (TTE) diastolic parameters (DPs) are used as non-invasive surrogates but have suboptimal accuracy. Left atrial expansion index (LAEI), describing LA reservoir function, could be used for indirectly estimate PCWP. Purpose To evaluate the correlation between LAEI and PCWP and to compare LAEI accuracy against DPs in estimating PCWP. Methods We retrospectively included the patients admitted to our department from 05/2015 to 02/2018 who underwent both a clinically indicated RHC and TTE within 24 hours. PCWP was obtained during RHC. DPs were measured offline and LAEI was calculated from LA maximum volume (MaxVol) and LA minimum volume (MinVol) as LAEI = [(LAMaxVol − LAMinVol) / LAMinVol)] × 100. Results We enrolled 405 patients (left ventricular ejection fraction (LVEF)&amp;lt;50% n=172; PCWP&amp;gt;12mmHg n=209). LAEI showed a logarithmic correlation with PCWP. The log-transformed LAEI (lnLAEI) had an excellent linear correlation (r=−0.82; p&amp;lt;0.001) with PCWP, higher than DPs (LAMaxVoli: r=0.42; E/A: r=0.57; E/e': r=0.51; TRMaxVel r=0.17; all p&amp;lt;0.001). lnLAEI had the highest accuracy in identifying PCWP&amp;gt;12 mmHg (lnLAEI AUC 0.921, p&amp;lt;0.001) when compared to DPs and their association (Figure). lnLAEI showed an independent and added predictive value in estimating PCWP in a model including atrial fibrillation (Afib), heart rate (HR), LVEF, mitral regurgitation (MR), LAMaxVoli, E/A, E/e' and TRMaxVel (Table). Conclusions LAEI is a simple parameter strongly associated with PCWP which might be used for PCWP estimation. Funding Acknowledgement Type of funding source: None

All-Time Modeling of Co-Current Spontaneous Water Imbibition Into Gas-Saturated Rocks Using a Novel Transition Time

Abstract Spontaneous imbibition (SI) into a porous medium is an important transport phenomenon in petroleum reservoir engineering. The study of spontaneous water imbibition is critical to predict the production performance in these reservoirs developed by waterflooding, especially in the fractured gas reservoirs with active aquifers. While some studies have been reported to characterize spontaneous water imbibition into gas-saturated rocks, they are either limited or inaccurate due to the fact that the existing models have specific assumptions that cannot be applied in other time intervals. To this end, we proposed a novel transition imbibition time t* and developed an all-time (including both early- and later-time SI) model to match the experimental SI data. Furthermore, we proposed a novel model to estimate capillary pressures at different water saturations and to characterize the water saturation profile in capillary-dominated stage. Comparison with the existing capillary pressure estimation models was performed to test the differences. The results demonstrated that the all-time model could fit the experimental imbibition data of the entire SI process satisfactorily. The new saturation model established in this paper can be well fitted with the water saturation profile measured by the X-ray computer tomography (CT) scanners. The results and findings from this work may be of great significance in many areas related to SI, particularly in the development of naturally fractured gas reservoirs with active aquifers.

Local Capillary Pressure Estimation Based on Curvature of the Fluid Interface – Validation with Two-Phase Direct Numerical Simulations

With the advancement of high-resolution three-dimensional X-ray imaging, it is now possible to directly calculate the curvature of the interface of two phases extracted from segmented CT images during two-phase flow experiments to derive capillary pressure. However, there is an inherent difficulty of this image-based curvature measurement: the use of voxelized image data for the calculation of curvature can cause significant errors. To address this, we first perform two-phase direct numerical simulations to obtain the oil and water phase distribution, the exact location of the interface, and local fluid pressure. We then investigate a method to compute curvature on the oil/water interface. The interface is defined in two ways. In one case the simulated interface which has a sub-resolution smoothness is used, while the other is a smoothed interface which is extracted from synthetic segmented data based on the simulated phase distribution. Computed mean curvature on these surfaces are compared with that obtained from the fluid pressure computed directly in the simulation. We discuss the accuracy of image-based curvature measurements for the calculation of capillary pressure and propose the best way to extract an accurate curvature measurement, quantifying the likely uncertainties.

Numerical simulation of film instability over low wettability surfaces through lubrication theory

A computational study of thin liquid films over a solid surface is reported. The lubrication equation is numerically solved using an in-house code, which implements the finite volume method. Small slope approximation is abandoned, and a more accurate model for capillary pressure estimation is presented, allowing us to correctly investigate higher contact angles, when compared to the maximum value allowed by small slope approximation. Disjoining pressure is used for modeling substrate wettability. The in-house solver is first validated: a 1D flowing film driven by gravity is simulated and the disjoining pressure model is verified for contact angles up to 60°; replicating literature experimental investigations, a uniform film covering an inclined plate is perturbed, inducing the generation of a large dry patch; rivulet buildup is simulated; and the numerical results are compared with fully 3D computations found in the literature and verified with analytical evidences. Then, a film flowing over an inclined plate bounded by lateral walls, which is a complex configuration commonly used for studying liquid behavior in structured packing, is investigated and relevant parameters are reported.

P2474Noninvasive estimation of pulmonary capillary wedge pressure by novel 3D speckle tracking echocardiography and validation study by cardiac catheterization

Abstract Background We previously reported that pulmonary capillary wedge pressure (PCWP) was noninvasively evaluated by 2D speckle tracking echocardiography (STE). Recently, novel software was introduced to examine volume and function of left ventricular and left atrium (LA) by 3D-STE automatically. Purpose We sought to compare the PCWP estimated by conventional 2D-STE (2D-ePCWP) and by novel 3D-STE (3D-ePCWP), and validate those values by cardiac catheterization. Methods Echocardiography and catheterization were performed in 29 patients (age 72±2) (7 ischemic heart disease, 2 hypertensive heart disease, 5 dilated cardiomyopathy, 12 valvular heart disease and 3 primary pulmonary hypertension).The ePCWP (mmHg) is noninvasively obtained as 10.8 − 12.4 x Log (left atrial active emptying function/minimum volume) as we previously reported. Echocardiography was performed just before the catheterization and we analyzed the 2D and 3D data by novel off-line software. 3D data was automatically analyzed and the border settings were fixed at default (ES60, ED30) (Figure). Results 2D-ePCWP and 3D-ePCWP had a good correlation with PCWP invasively obtained by catheterization (r=0.87 and 0.83, respectively, both p&lt;0.001). There was an excellent correlation between 2D-ePCWP and 3D-ePCWP (r=0.94, p&lt;0.001) and there was a good correlation between 2D-LA volume index and 3D- LA volume index (r=0.80, p&lt;0.001). Bland-Altman analysis revealed a good agreement between 2D-ePCWP and 3D-ePCWP, and between 2D-ePCWP and 3D-ePCWP without fixed and proportional bias. Conclusion This study demonstrated that PCWP might be noninvasively assessed by not only 2D-STE but also 3D-STE with reasonable accuracy and 3D-STE might have utility and value in the routine clinical practice.

Capillary pressure and relative permeability estimation for low salinity waterflooding processes using pore network models

In this work, the effect of low salinity waterflooding (LSWF) on capillary pressure and relative permeability is studied at pore scale. For this purpose, a pore-scale model implemented on OpenPNM is developed to describe fluid flow, salinity transport and wettability change in a pore network. The effect is studied by considering high salinity waterflooding followed by low salinity waterflooding. The system wettability change is introduced as modifications of the local contact angle that are induced by the water salinity reduction. These modifications are evaluated by calculating the contact angle change in each pore and throat of the network, and then integrating it. From this analysis, a methodology has been developed to study the LSWF impact on capillary pressure and relative permeability. This methodology has been successfully applied to two pore network cases available in an open rock data base; one network correspond to a sandstone and the other to a carbonate sample. The methodology developed here can be seen as a tool to complement laboratory tests needed to determine the efficiency of LSWF processes.

Analytical Pore-Network Approach (APNA): A novel method for rapid prediction of capillary pressure-saturation relationship in porous media

The relationship between capillary pressure and wetting fluid saturation is one of the most important functions required for the modelling of immiscible displacement within porous media. Commonly, time consuming laboratory experiments or computationally expensive pore-scale numerical simulations are performed to estimate capillary pressure− saturation relationships for a given porous media. In this research, we introduce Analytical Pore-Network Approach (APNA): a new method to forecast capillary pressure-saturation relationships in porous media. APNA is a fully coupled analytical model, that is derived using the concept of Representative Elementary Volume (REV), and underpinned by geometrical analysis of the studied pore network using pore-scale images collected by a range of imaging modalities (e.g. thin section photomicrograph, x-ray micro computed tomography, confocal microscopy, etc.). In comparison to conventional laboratory measurements and numerical simulation techniques, APNA is trivial to implement, and is capable of providing rapid estimates of capillary pressure− saturation relationships for a broad range of porous materials. We validated APNA against empirical capillary pressure− saturation data published in the literature, revealing satisfactory agreement between APNA and the experimental studies.

Estimation of Pulmonary Capillary Wedge Pressure from the HVAD Waveform and Its Prognostic Implications

Purpose Flow waveform visualization is a unique feature of the HVAD left ventricular assist device (LVAD) that provides graphical real-time information linking device performance with patient hemodynamics. A previous study demonstrated a good correlation between the slope of the ventricular filling phase (VFPS) and the pulmonary capillary wedge pressure (PCWP). We aimed to validate the utility of VFPS to estimate PCWP and predict clinical outcomes. Methods In this prospective blinded study, screenshots from the HVAD monitor and simultaneous invasive hemodynamic measurements were obtained. Each screenshot was digitized (IGOR Pro, WaveMetrics Inc., Oswego, OR) and the VFPS was calculated for each screenshot (Figure 1A) by two independent readers who were blinded to the hemodynamic results. VFPS and the estimated PCWP [using the previously derived equation: PCWP = 7.05 +1.38 × (VFPS)] were correlated to the measured PCWP. Association between VFPS and heart failure (HF) readmission rates was evaluated. Results 107 sets of simultaneous measurements (VFPS and PCWP) were performed (mean age 55 years, 47% male). Prospectively collected VFPS had a very strong and significant correlation with PCWP (p 2 = 0.69). The previously proposed cutoff of VFPS ≥5.8 L/min/sec predicted PCWP ≥18 mmHg with 91.5% sensitivity and 95.2% specificity. The previously derived equation had significant correlation with measured PCWP (p 2 = 0.68; Figure 1B) and acceptable agreement with the measured PCWP (Figure 1C). Patients with VFPS ≥5.8 L/min/sec had significant higher HF readmission rates than those with VFPS Conclusion VFPS of the HVAD flow waveform is a novel noninvasive parameter that can estimate PCWP and predict HF readmissions. VFPS may aid in clinical management of HVAD patients and serve as a step in the development of a smart LVAD pump.

Clinical Usefulness of an Echo-Doppler Model in Predicting Elevated Pulmonary Capillary Wedge Pressure in Patients With Heart Failure

Although several tissue-Doppler imaging (TDI) models for pulmonary capillary wedge pressure (PCWP) estimation have been reported, their reliability remains uncertain. Our previous theoretical and experimental analyses suggest that right atrial pressure (RAP) corrected by tissue-Doppler imaging tricuspid/mitral annular peak systolic velocities (ST/SM) (RAP × ST/SM) reliably predicts elevated PCWP. We sought to investigate its clinical usefulness for predicting elevated PCWP in heart failure (HF) patients. Ninety-eight patients admitted with HF who underwent right heart catheterization were prospectively studied. RAP and PCWP were measured by right heart catheterization. Simultaneously, ST/SM, early diastolic transmitral flow velocity to mitral annular velocity ratio (E/Ea), and diameter of inferior vena cava at inspiration (IVCDi), a noninvasive surrogate for RAP, were measured by echocardiography. RAP correlated with IVCDi (R2 = 0.57). A significantly stronger correlation was observed between IVCDi corrected by ST/SM (IVCDi × ST/SM) and PCWP than between E/Ea and PCWP (R2 = 0.47 vs 0.18). Receiver-operating characteristic analyses indicated that IVCDi × ST/SM >16 mm predicted PCWP >18 mm Hg with 90% sensitivity and 77% specificity, and the area under the curve was 0.86, which was significantly larger than that of E/Ea (area under the curve=0.72). In conclusions, IVCDi × ST/SM is a new useful noninvasive model to predict elevated PCWP in HF patients.