Pressure Volume Research Articles

Acoustic properties, elasticity, and equation of state of glycerol under pressure.

We employed high-pressure Brillouin scattering to study the pressure dependencies of acoustic modes of glycerol up to 14GPa at 300K. We observed longitudinal acoustic velocities and transverse acoustic velocities for the first time from 5 to 14GPa. The results allow the determination of a complete set of elastic properties and an accurate determination of the pressure-volume (P-V) equation of state (EOS). EOS parameters, K0 = 14.9 ± 1.8GPa and K'0 = 5.6 ± 0.5, were determined from fits to the data from ambient pressure to 14GPa. Direct volume measurements of the P-V EOS are consistent with those determined by Brillouin scattering. A deviation from a Cauchy-like relationship for elastic properties was observed, and the pressure dependencies of the photoelastic constants and relaxation times were documented from 5 to 14GPa. These results have broad implications for glass-forming liquids, viscoelastic theory, and mode coupling theory.

State-of-the-art methodologies used in preclinical studies to assess left ventricular diastolic and systolic function in mice, pitfalls and troubleshooting.

Cardiovascular diseases (CVD) are still the leading cause of death worldwide. The improved survival of patients with comorbidities such as type 2 diabetes, hypertension, obesity together with the extension of life expectancy contributes to raise the prevalence of CVD in the increasingly aged society. Therefore, a translational research platform that enables precise evaluation of cardiovascular function in healthy and disease condition and assess the efficacy of novel pharmacological treatments, could implement basic science and contribute to reduce CVD burden. Heart failure is a deadly syndrome characterized by the inability of the heart to meet the oxygen demands of the body (unless there is a compensatory increased of filling pressure) and can manifest either with reduced ejection fraction (HFrEF) or preserved ejection fraction (HFpEF). The development and progression of HFrEF is mostly attributable to impaired contractile performance (systole), while in HFpEF the main problem resides in decreased ability of left ventricle to relax and allow the blood filling (diastole). Murine preclinical models have been broadly used in research to understand pathophysiologic mechanisms of heart failure and test the efficacy of novel therapies. Several methods have been employed to characterise cardiac systolic and diastolic function including Pressure Volume (PV) loop hemodynamic analysis, echocardiography and Magnetic Resonance Imaging (MRI). The choice of one methodology or another depends on many aspects including budget available, skills of the operator and design of the study. The aim of this review is to discuss the importance of several methodologies that are commonly used to characterise the cardiovascular phenotype of preclinical models of heart failure highlighting advantages and limitation of each procedure. Although it requires highly skilled operators for execution, PV loop analysis represents the "gold standard" methodology that enables the assessment of left ventricular performance also independently of vascular loading conditions and heart rate, which conferee a really high physiologic importance to this procedure.

Optimization of shale gas fracturing parameters based on artificial intelligence algorithm

Resource-rich shale gas plays a pivotal role in new energy types. The key to scientifically and efficiently developing shale gas fields is to clarify the main factors that affect the production of shale gas wells. In this paper, according to the shale gas reservoir characteristic of the Fuling marine Longmaxi Formation, a single-well geological model was established using the reservoir numerical simulation software CMG. Then, 10,000 different reservoir models were randomly generated for different formation physical parameters, completion parameters, and fracturing parameters using the Monte Carlo method, and these 10,000 models were simulated numerically. The machine learning model uses a dataset of 10,000 different geological, completion, and fracturing parameters as input and 10,000 production curves as output. Multiple machine learning regression methods were used to train and test the dataset, and the optimal method (GBDT algorithm) was selected, and the accuracy R2 of the test set of the GBDT prediction model is 0.96. A fracturing parameter optimization workflow was constructed by combining a production prediction model with a particle swarm optimizer (PSO). The process can quickly optimize the fracturing parameters and predict the production for each time by targeting the cumulative gas production under different geological conditions. The optimized parameters are Fracture Spacing, Fracture Width, Intrinsic Permeability, Fracture Half-length, Langmuir Pressure, and Langmuir Volume. The initial predicted cumulative gas production was 4.59 × 108 m3, which was optimized to 4.90 × 108 m3. The proposed PSO-GBDT proxy model can instantly predict the production of shale gas wells with considerable accuracy, reliability, and efficiency, which is a vital tool for optimizing fracture design. This investigation provides a solid foundation for predicting the production of unconventional gas reservoirs and for parameter optimization.

Abstract P2008: Contractile Adaptation Of The Right Ventricular Myocardium In Pulmonary Hypertension

Introduction: Pulmonary hypertension (PH) is characterized by increased right ventricular (RV) afterload inducing notable biomechanical remodeling in the RV free wall (RVFW) myocardium. While changes in the passive behavior of the RVFW have been studied, its contractile adaptations in PH remain to be investigated. Methods: Two sugen-hypoxia models were developed by injecting SU5416 into Sprague Dawley (SD) and Fischer (CDF) rats (n=4 each) and placing them in a hypoxia chamber for 3 weeks, followed by 1 week of normoxia. Wild-type rats (n=4), injected with vehicle and kept in normoxia, were used as controls. Right heart catheterization was perfomed at week 4. RVFW samples were skinned in 10% Triton. Samples were activated at pCa 4.5. Mechanical tests were performed isometrically at 20% stretch. Circumferential and longitudinal stresses were summed to report ensemble stress. Results: RV systolic pressure and stroke volume showed significant increase and decrease in both PH groups, respectively, compared to controls (Figs. 1A, B). While increases in initial stress, representing the passive behavior, did not reach significance in either PH group (Fig. 1C), total stress, representing the combined passive and active behavior, increased significantly only in CDF-PH group (Fig. 1D), known to exhibit a more maladaptive RV remodeling compared to SD-PH. Select stresses are shown in Figs. 1E, F. Conclusions: While elevated passive stresses in the RVFW are commonly reported in PH, the measurement of contractile stresses is essential to properly assess the adaptation of the RV. Further studies are needed to determine the role of passive vs. active stresses in the outcome of RV remodeling.

Abstract P3077: Withdrawal Of High Fat Diet And L-NAME Dampens T Cell Activation And Ameliorates Pathology In Experimental Heart Failure With Preserved Ejection Fraction (HFPEF) Through Modulation Of The T Cell IRE1a-XBP1 Axis

Introduction: Cardiometabolic HFpEF is characterized by T cell systemic inflammation and can be modeled preclinically with high fat diet (HFD) and L-NAME. Metabolic perturbations can alter T cell function through modulation of the unfolded protein response (UPR). How T cells are activated in HFpEF and whether T cell inflammation can be tuned by removing cardiometabolic stress remains unknown. Hypothesis: HFD and L-NAME induce reversible alterations in T cell UPR signaling that modulate T cell dependent cardiac inflammation and pathology in experimental HFpEF. Methods: Male C57/BL6J mice (wild-type, WT), OT-II antigen restricted mice, and CD4 Cre Xbp1 fl/fl mice were fed a high-fat diet (HFD) and L-NAME (H/L) for 5 weeks. WT mice were switched to standard diet (STD) for two additional weeks. WT mice receiving HFD or L-NAME only, or TAC surgery (a model of HF with reduced EF) were used as controls. Left ventricular (LV) end diastolic pressure volume relationship (EDPVR) was assessed using invasive hemodynamic analyses and LV EF by echocardiography. Cardiac and splenic T cells were characterized by flow cytometry and T cell UPR was evaluated by qPCR and Western blot. Results: 5 weeks of H/L was sufficient to induce cardiac T cell infiltration and splenic T cell activation. OTII mice fed H/L showed increased cardiac CD4 + T cell infiltration compared to STD controls, indicating T cell activation is not cardiac antigen restricted. Furthermore, splenic T cell characterization revealed H/L resulted in decreased phosphorylation of the UPR protein inositol-requiring enzyme 1α (IRE1α) and reduced expression of X box-binding protein 1 ( Xbp1s/u ) compared to T cells from mice exposed to HFD or L-NAME alone, STD, or WT TAC controls. CD4 Cre+ Xbp1 fl/fl mice (T cell Xbp1 -/- ) fed with H/L had increased cardiac T cell infiltration compared to Cre - controls. Lastly, Xbp1s expression in splenic CD4 + T cells was recovered after withdrawal of H/L and resulted in partial reduction of cardiac hypertrophy, decreased EDPVR, as well as less cardiac T cell infiltration compared to mice kept on H/L. Conclusions: Reversible downregulation of the T cell IRE1α-XBP1 axis is a unique T cell signature of HFpEF that contributes to T cell inflammation and adverse cardiac remodeling.

Analysis of Reported Adverse Events Associated With the Use of Functional Lumen Imaging Probe Devices in the Esophagus and Stomach: An FDA MAUDE Database Study

The endoscopic Functional Lumen Imaging Probe (FLIP) devices are used to evaluate pressure changes, diameter, and volume of the esophagus. We used the FDA’s MAUDE database to collect post-marketing surveillance data on these devices from January 2009 to September 2022. Forty-Five device-related events and thirty-six patient-related adverse events were analyzed. The most common device issue for the diagnostic FLIP device was therapeutic/diagnostic failure (n = 6), while the most frequent issue with the therapeutic FLIP device was adverse events without an identified device or use problem (n = 11). Patient-related adverse events were extremely rare with the diagnostic FLIP and the most common patient-related adverse event with the therapeutic FLIP was perforation (n = 11). Endoscopists need to be mindful of these potential technical issues and adverse events while using these devices.

Right Atrial Adaptation to Precapillary Pulmonary Hypertension: Pressure-Volume, Cardiomyocyte, and Histological Analysis

BackgroundPrecapillary pulmonary hypertension (precPH) patients have altered right atrial (RA) function and right ventricular (RV) diastolic stiffness. ObjectivesThis study aimed to investigate RA function using pressure-volume (PV) loops, isolated cardiomyocyte, and histological analyses. MethodsRA PV loops were constructed in control subjects (n = 9) and precPH patients (n = 27) using magnetic resonance and catheterization data. RA stiffness (pressure rise during atrial filling) and right atrioventricular coupling index (RA minimal volume / RV end-diastolic volume) were compared in a larger cohort of patients with moderate (n = 39) or severe (n = 41) RV diastolic stiffness. Cardiomyocytes were isolated from RA tissue collected from control subjects (n = 6) and precPH patients (n = 9) undergoing surgery. Autopsy material was collected from control subjects (n = 6) and precPH patients (n = 4) to study RA hypertrophy, capillarization, and fibrosis. ResultsRA PV loops showed 3 RA cardiac phases (reservoir, passive emptying, and contraction) with dilatation and elevated pressure in precPH. PrecPH patients with severe RV diastolic stiffness had increased RA stiffness and worse right atrioventricular coupling index. Cardiomyocyte cross-sectional area was increased 2- to 3-fold in precPH, but active tension generated by the sarcomeres was unaltered. There was no increase in passive tension of the cardiomyocytes, but end-stage precPH showed reduced number of capillaries per mm2 accompanied by interstitial and perivascular fibrosis. ConclusionsRA PV loops show increased RA stiffness and suggest atrioventricular uncoupling in patients with severe RV diastolic stiffness. Isolated RA cardiomyocytes of precPH patients are hypertrophied, without intrinsic sarcomeric changes. In end-stage precPH, reduced capillary density is accompanied by interstitial and perivascular fibrosis.

Effect of modified high-flow oxygen therapy on positive end-expiratory pressure and end-expiratory lung volume based on simulated lung platform

ObjectiveThe aim of this study was to assess the effect of modified high-flow oxygen therapy on end-expiratory lung volume (EELV) and positive end-expiratory pressure (PEEP) in tracheotomized patients with normal pulmonary, acute hypoxic respiratory failure (AHRF) or chronic obstructive pulmonary disease (COPD). MethodsA ventilator and an artificial lung model were used to simulate the normal or strong inspiratory effort state of normal lung, AHRF and COPD patients. The traditional high-flow respiratory humidification therapy device connected with a standard interface (group A), and the modified therapy device added two types of resistance valves (group B, inner diameter 7.7 mm, length 24.0 mm; group C, inner diameter 7.7 mm, length 34.0 mm) to the exhalation end of the standard interface. The changes of end-expiratory lung volume (ΔEELV) and PEEP with the increase of flow rate (10 L/min, 20 L/min, 30 L/min, 40 L/min, 50 L/min, 60 L/min) in the three groups was recorded. ResultsUnder simulated conditions of normal lung, AHRF and COPD, as the flow rate increased by using the modified therapy device, the PEEP values in all groups showed an exponential increasing trend, and the ΔEELV also increased accordingly. In addition, under the same flow rate level, the PEEP values of the two modified high-flow oxygen therapies (Group B and Group C) were significantly higher than those of the standard high-flow oxygen therapy (Group A) (p < 0.05). In the normal lung model with normal or strong inspiratory effort, and in the AHRF or COPD model with strong inspiratory effort, when the flow rate was higher than 30 L/min, the PEEP levels of Group B were significantly lower than those of Group C (p < 0.05). In the AHRF model with normal inspiratory effort, when the flow rate was between 10 L/min and 60 L/min, the PEEP levels of Group B were significantly lower than those of Group C (p < 0.05). Moreover, in the COPD model with normal inspiratory effort, the PEEP levels of Group B were significantly lower than that of Group C only when the flow rate was 60 L/min (p < 0.05). ConclusionThe addition of different types of resistance valves to the high-flow exhalation end may be a feasible solution to improve the clinical efficacy of tracheotomized high-flow oxygen therapy.

High-Pressure Vibrational and Structural Studies of the Chemically Engineered Ferroelectric Phase of Sodium Niobate

Pure NaNbO3 has an antiferroelectric phase at ambient pressure. The structural behaviour of the chemically engineered ferroelectric phase of sodium niobate, NNBT05: [(0.95) NaNbO3-(0.05) BaTiO3], under high-pressure has been studied using Raman scattering and angle-dispersive synchrotron X-ray diffraction techniques. At pressure &gt; 1 GPa, noticeable changes in the Raman spectra can be seen in the low wavenumber modes (150–300 cm−1). Large changes in the positions and intensities of the Raman bands as a function of pressure provide evidence for structural phase transition. The results indicate significant changes in the bond-lengths and the orientation of the NbO6 octahedra at ~1 GPa, and a transition to the paraelectric phase at ~5 GPa, which are at lower pressures than previously found in pure NaNbO3. The powder X-ray diffraction pattern shows an appreciable change in the peak profile in terms of position and width on increasing pressure. The pressure dependences of the structural parameters show that the response of the lattice parameters to pressure is strongly anisotropic. By fitting the pressure–volume data using the Birch–Murnaghan equation of state, the isothermal bulk modulus was estimated. The experimental results suggest that on doping BaTiO3 in NaNbO3, the bulk modulus increases. The bulk modulus of NNBT05 has been estimated to be 164.5 GPa, which is fairly close to 157.5 GPa, as previously observed in NaNbO3.

Use of a Portable Mechanical Ventilator during Cardiopulmonary Resuscitation is Feasible, Improves Respiratory Parameters, and Prevents the Decrease of Dynamic Lung Compliance.

For practical and protective ventilation during cardiopulmonary resuscitation (CPR), a 150-grams mechanical ventilator (VLP2000E) that limits peak inspiratory pressure (PIP) during simultaneous ventilation with chest compressions was developed. To evaluate the feasibility of VLP2000E ventilation during CPR and to compare monitored parameters versus bag-valve ventilation. A randomized experimental study with 10 intubated pigs per group. After seven minutes of ventricular fibrillation, 2-minute CPR cycles were delivered. All animals were placed on VLP2000E after achieving return of spontaneous circulation (ROSC). Bag-valve and VLP2000E groups had similar ROSC rate (60% vs. 50%, respectively) and arterial oxygen saturation in most CPR cycles, different baseline tidal volume [0.764 (0.068) vs. 0.591 (0.123) L, p = 0.0309, respectively] and, in 14 cycles, different PIP [52 (9) vs. 39 (5) cm H2O, respectively], tidal volume [0.635 (0.172) vs. 0.306 (0.129) L], ETCO2[14 (8) vs. 27 (9) mm Hg], and peak inspiratory flow [0.878 (0.234) vs. 0.533 (0.105) L/s], all p < 0.0001. Dynamic lung compliance (≥ 0.025 L/cm H2O) decreased after ROSC in bag-valve group but was maintained in VLP2000E group [0.019 (0.006) vs. 0.024 (0.008) L/cm H2O, p = 0.0003]. VLP2000E ventilation during CPR is feasible and equivalent to bag-valve ventilation in ROSC rate and arterial oxygen saturation. It produces better respiratory parameters, with lower airway pressure and tidal volume. VLP2000E ventilation also prevents the significant decrease of dynamic lung compliance observed after bag-valve ventilation. Further preclinical studies confirming these findings would be interesting.

Airflow and dynamic circumference of abdomen and thorax for adults at varied continuous positive airway pressure ventilation settings and breath rates

Continuous positive airway pressure (CPAP) ventilation is a commonly prescribed respiratory therapy providing positive end-expiratory pressure (PEEP) to assist breathing and prevent airway collapse. Setting PEEP is highly debated and it is thus primarily titrated based on symptoms of excessive or insufficient support. However, titration periods are clinician intensive and can result in barotrauma or under-oxygenation during the process. Developing model-based methods to more efficiently personalise CPAP therapy based on patient-specific response requires clinical data of lung/CPAP interactions. To this end, a trial was conducted to establish a dataset of healthy subjects lung/CPAP interaction. Pressure, flow, and tidal volume were recorded alongside secondary measures of dynamic chest and abdominal circumference, to better validate model outcomes and assess breathing modes, muscular recruitment, and effort. N = 30 subjects (15 male; 15 female) were included. Self-reported asthmatics and smokers/vapers were included, offering a preliminary assessment of any potential differences in response to CPAP from lung stiffness changes in these scenarios. Additional demographics associated with lung function (sex, age, height, and weight) were also recorded.

Comparison of the Y-pouch orthotopic neobladder and the Studer technique after radical cystectomy: surgical and functional outcomes from a single-center series

BackgroundTo explore a method of constructing an orthotopic ileal neobladder (ONB) in the Y-pouch configuration. We describe the steps followed to create the Y-pouch ileal orthotopic neobladder (ONB) and compared the perioperative, functional, and urodynamics outcomes with the Studer neobladder technique.MethodsA retrospective cohort study of 90 bladder cancer patients, who received open radical cystectomy with the ONB performed at a hospital from June 2009 to May 2020. These patients were divided into two groups—the Y-pouch and the Studer neobladder groups. Perioperative, functional outcome, complication, renal function data outcomes, and pressure–volume study were used to evaluate the treatment outcomes after a radical cystectomy.ResultsNinety patients (54 Studer and 36 Y-pouch neobladder) were enrolled. The median patient age was 62.6 (± 11) years. The mean operative time for the Studer technique was 290 (242.5–350) min, and the Y-pouch technique was 300 (271.2–335) min) (p = 0.826). At 30 days postoperatively, the Clavien-Dindo classification of surgical complications revealed grade-2 urinary infections in two patients (5.6%) and six patients (11.1%) for the Y-pouch and Studer techniques, respectively. Intermediate complications (30–90 days) were reported in 4 (11.1%) and 18 patients (44.4%) in the Y-pouch and the Studer techniques, respectively (p = 0.062). In the urodynamics study (UDS), the Y-pouch group had a mean postvoid residual volume of 20 mL and Studer of 40 ml (p = 0.06). A mean capacity of 462 (380–600) mL compares to the Studer neobladder group with 495 (400–628) mL. The average mean compliance of the Studer group was 35.5 (28–52) ml/cm H2O and 33 (30–43) ml/cm H2O for Y pouch, and most patients had > 30 ml/cm H2O compliance (80/90 patients).ConclusionsThe Y-pouch neobladder technique in an RC with an orthotopic neobladder provides perioperative and functional outcomes compared to those of the Studer orthotopic neobladder resulting in similar intermediate-term. Therefore, the Y-pouch ileal neobladder is both feasible and safe to be used as a standard neobladder technique for urinary diversion in patients with bladder cancer undergoing radical cystectomy and needs confirmation with long-term results.

Virtual patient with temporal evolution for mechanical ventilation trial studies: A stochastic model approach

Background and objectiveHealthcare datasets are plagued by issues of data scarcity and class imbalance. Clinically validated virtual patient (VP) models can provide accurate in-silico representations of real patients and thus a means for synthetic data generation in hospital critical care settings. This research presents a realistic, time-varying mechanically ventilated respiratory failure VP profile synthesised using a stochastic model. MethodsA stochastic model was developed using respiratory elastance (Ers) data from two clinical cohorts and averaged over 30-minute time intervals. The stochastic model was used to generate future Ers data based on current Ers values with added normally distributed random noise. Self-validation of the VPs was performed via Monte Carlo simulation and retrospective Ers profile fitting. A stochastic VP cohort of temporal Ers evolution was synthesised and then compared to an independent retrospective patient cohort data in a virtual trial across several measured patient responses, where similarity of profiles validates the realism of stochastic model generated VP profiles. ResultsA total of 120,000 3-hour VPs for pressure control (PC) and volume control (VC) ventilation modes are generated using stochastic simulation. Optimisation of the stochastic simulation process yields an ideal noise percentage of 5–10% and simulation iteration of 200,000 iterations, allowing the simulation of a realistic and diverse set of Ers profiles. Results of self-validation show the retrospective Ers profiles were able to be recreated accurately with a mean squared error of only 0.099 [0.009–0.790]% for the PC cohort and 0.051 [0.030–0.126]% for the VC cohort. A virtual trial demonstrates the ability of the stochastic VP cohort to capture Ers trends within and beyond the retrospective patient cohort providing cohort-level validation. ConclusionVPs capable of temporal evolution demonstrate feasibility for use in designing, developing, and optimising bedside MV guidance protocols through in-silico simulation and validation. Overall, the temporal VPs developed using stochastic simulation alleviate the need for lengthy, resource intensive, high cost clinical trials, while facilitating statistically robust virtual trials, ultimately leading to improved patient care and outcomes in mechanical ventilation.

Structure evolution of Bi4O7 under high pressure

X-ray diffraction and Raman spectroscopy measurements were used to study the structure evolution of Bi4O7 during compression. Two isostructural phase transitions were observed under high pressure, with the first transition to phase II occurring at approximately 3.0 (2) GPa and the second to phase III occurring at approximately 13.0 (5) GPa. The pressure–volume (P–V) curve was found to be discontinuous at those two pressure transition boundaries. By fitting the P–V curves in three different stages, the bulk moduli were estimated to be approximately 101 (2), 68 (2) and 172 (3) GPa. Such large differences in the bulk moduli confirm two isostructural phase changes in the three stages. An irreversible amorphization process was found to start at approximately 20 (1) GPa, and the sample gradually becomes fully amorphous during compression at 30 (1) GPa.

The equations of state of statically compressed palladium and rhodium

The pressure–volume equations of state of palladium and rhodium statically compressed in neon are presented. Vinet fits give parameters for palladium: V0=58.678(73) Å3, B0=189.3(30) GPa, B0′=5.473(63), and rhodium: V0=55.062(63) Å3, B0=241.3(65) GPa, B0′=5.34(24). Both metals are observed to react with hydrocarbons under pressure to form hydrides. Existing equations of state are discussed with regard to potential inadvertent hydrogen contamination as a source for discrepancies and anomalous fitted parameters.

Pressure-Volume Loop Analysis of Voiding Workload: An Application in Trans-Vaginal Mesh-Repaired Pelvic Organ Prolapse Patients.

Although trans-vaginal mesh (TVM) offers a successful anatomical reconstruction and can subjectively relieve symptoms/signs in pelvic organ prolapse (POP) patients, its objective benefits to the voiding function of the bladder have not been well established. In this study, we investigated the therapeutic advantage of TVM on bladder function by focusing on the thermodynamic workload of voiding. The histories of 31 POP patients who underwent TVM repair were retrospectively reviewed. Cystometry and pressure volume analysis (PVA) of the patients performed before and after the operation were analyzed. TVM postoperatively decreased the mean voiding resistance (mRv, p < 0.05, N = 31), reduced the mean and peak voiding pressure (mPv, p < 0.05 and pPv, p < 0.01, both N = 31), and elevated the mean flow rate (mFv, p < 0.05, N = 31) of voiding. While displaying an insignificant effect on the voided volume (Vv, p < 0.05, N = 31), TVM significantly shortened the voiding time (Tv, p < 0.05, N = 31). TVM postoperatively decreased the loop-enclosed area (Apv, p < 0.05, N = 31) in the PVA, indicating that TVM lessened the workload of voiding. Moreover, in 21 patients who displayed postvoiding urine retention before the operation, TVM decreased the residual volume (Vr, p < 0.01, N = 21). Collectively, our results reveal that TVM postoperatively lessened the workload of bladder voiding by diminishing voiding resistance, which reduced the pressure gradient required for driving urine flow.

Predictors of fluid responsiveness in the operating room: a narrative review.

Prediction of fluid responsiveness has been considered an essential tool for modern fluid management. However, most studies in this field have focused on patients in intensive care unit despite numerous research throughout several decades. Therefore, the present narrative review aims to show the representative method's feasibility, advantages, and limitations in predicting fluid responsiveness, focusing on the operating room environments. Firstly, we described the predictors of fluid responsiveness based on heart-lung interaction, including pulse pressure and stroke volume variations, the measurement of respiratory variations of inferior vena cava diameter, and the end-expiratory occlusion test and addressed their limitations. Subsequently, the passive leg raising test and mini-fluid challenge tests were also mentioned, which assess fluid responsiveness by mimicking a classic fluid challenge. In the last part of this review, we pointed out the pitfalls of fluid management based on fluid responsiveness prediction, which emphasized the importance of individualized decision-making. Understanding the available representative methods to predict fluid responsiveness and their associated benefits and drawbacks through this review will aid anesthesiologists in choosing the most reliable methods for optimal fluid administration in each patient during anesthesia in the operating room.

Biventricular Interaction During Acute Left Ventricular Ischemia in Mice: A Combined In-Vivo and In-Silico Approach

Computational models provide an efficient paradigm for integrating and linking multiple spatial and temporal scales. However, these models are difficult to parameterize and match to experimental data. Recent advances in both data collection and model analyses have helped overcome this limitation. Here, we combine a multiscale, biventricular interaction model with mouse data before and after left ventricular (LV) ischemia. Sensitivity analyses are used to identify the most influential parameters on pressure and volume predictions. The subset of influential model parameters are calibrated to biventricular pressure–volume loop data (n = 3) at baseline. Each mouse underwent left anterior descending coronary artery ligation, during which changes in fractional shortening and RV pressure–volume dynamics were recorded. Using the calibrated model, we simulate acute LV ischemia and contrast outputs at baseline and in simulated ischemia. Our baseline simulations align with the LV and RV data, and our predictions during ischemia complement recorded RV data and prior studies on LV function during myocardial infarction. We show that a model with both biventricular mechanical interaction and systems-level cardiovascular dynamics can quantitatively reproduce in-vivo data and qualitatively match prior findings from animal studies on LV ischemia.

Application of Multiobjective Optimization in the Analysis of the Performance of Different Temperature Functions for a Generalized Cubic Equation of State

Since the emergence of van der Waals equation of state, several equations have been proposed to represent the behavior of pure compounds and mixtures, such as GEOS, which is a new generalized cubic equation of state form that employs a temperature function dependent on two or three adjustable parameters. Recently, multiobjective optimization has started to be applied in equations of state for parameters estimation, due to the conflicting nature of the objective functions. This methodology is attractive because it can be used to compare different models or variants of the same problem, through the trade-off analysis of the so-called Pareto front. In this context, the multiobjective PSO algorithm, based on the Pareto dominance principle, is used in this work for estimating the parameters of the generalized cubic equation of state, by fitting its results to synthetic experimental data of vapor pressure and saturated liquid volume. The performance of the new estimated parameters of the three temperature functions is investigated through the calculation of thermodynamic properties of interest in industry and academia. In addition, comparisons against real experimental data available in the literature are performed.

A biomechanics-based parametrized cardiac end-diastolic pressure–volume relationship for accurate patient-specific calibration and estimation

A simple power law has been proposed in the pioneering work of Klotz et al. (Am J Physiol Heart Circ Physiol 291(1):H403–H412, 2006) to approximate the end-diastolic pressure–volume relationship of the left cardiac ventricle, with limited inter-individual variability provided the volume is adequately normalized. Nevertheless, we use here a biomechanical model to investigate the sources of the remaining data dispersion observed in the normalized space, and we show that variations of the parameters of the biomechanical model realistically account for a substantial part of this dispersion. We therefore propose an alternative law based on the biomechanical model that embeds some intrinsic physical parameters, which directly enables personalization capabilities, and paves the way for related estimation approaches.