Fluid Loading Research Articles

Validity of Pleth Variability Index to Predict Fluid Responsiveness in Patients Undergoing Cervical Spine Surgery in the Modified Prone Position

Background and Objective: The modified prone position, which is an alteration of the standard prone position, reduces cardiac preload. Dynamic variables including stroke volume variation (SVV), pulse pressure variation (PPV), and pleth variability index (PVI) are reliable predictors for fluid responsiveness during surgery. To the best of our knowledge, no studies assessing dynamic variables for fluid responsiveness have been conducted in the modified prone position. This study aimed to evaluate the ability of PVI to predict fluid responsiveness in the modified prone position during cervical spine surgery. Materials and Methods: PVI, SVV, and PPV were recorded at the following times: before and after a 4 mL/kg crystalloid load in the supine position (T1, T2); after placement in the modified prone position (T3); and before and after a 4 mL/kg crystalloid administration in the modified prone position (T4, T5). Fluid responsiveness was defined as stroke volume (SV) ≥ 15%, assessed by the FloTrac/Vigileo™ (Edwards Lifesciences Corp, Irvine, CA, USA). Receiver operating characteristic (ROC) curves were analyzed to identify changes in each dynamic variable that could predict fluid responsiveness in the modified prone position. Results: Data from a total of 43 subjects were analyzed. In the supine position, 21 subjects were responders. After subjects were placed in the modified prone position, SV significantly decreased, while PVI, SVV, and PPV significantly increased (p < 0.001 for all). In the modified prone position, 13 subjects were responders, and the areas under the ROC curves for ΔPVI, ΔSVV, and ΔPPV after fluid loading were 0.524 (95% confidence interval [CI] 0.329–0.730, p = 0.476), 0.749 (95% CI 0.566–0.931, p = 0.004), and 0.790 (95% CI 0.641–0.938, p < 0.001), respectively. Conclusions: Crystalloid pre-loading could not mitigate the decrease in SV caused by the modified prone position. Changes in PVI were less reliable in predicting fluid responsiveness in the modified prone position.

Physiological impact of oral carbohydrate preload in healthy volunteers.

Oral carbohydrate loading has become a key component of Enhanced Recovery After Major Surgery (ERAS) pathways, with potential improvements in patient comfort, nausea and vomiting, ileus and length of stay. The contribution of each component of ERAS, including carbohydrate beverages, remains unclear. We aimed to determine the impact of standardized oral carbohydrate fluid loading on haemodynamics, stroke volume and gastric state in a group of healthy volunteers. Twenty-three volunteer participants free of known cardiovascular or gastrointestinal disease, consumed 400 mL of a proprietary carbohydrate solution. Heart rate (HR), blood pressure (BP), stroke volume (SV) and gastric cross-sectional area (CSA) were measured with bedside ultrasound at baseline, 30/60/120 min post-ingestion. There were small decreases in HR, BP (<10%) that were statistically significant. There were small increases (<10%) in SV at 30 and 60 min post-ingestion, but SV had returned to baseline by 120 min. There were no changes in SV variation. Gastric CSA increased immediately post-ingestion, then decreased in a linear fashion before returning to baseline by 120 min. In a standard 400 mL dose of a carbohydrate beverage, only small increases in SV could be demonstrated in the first-hour post-ingestion. All patients had largely returned to their baseline SV and gastric CSA state within 2 h post-fluid ingestion. A mild decrease in HR and BP was noted that persisted at 120 min. A 400 mL carbohydrate beverage does not appear to have favourable cardiovascular effects in a healthy population.

Forced vibrations of a FGM thin-walled cylinder under fluid loading

Forced vibrations of a FGM thin-walled cylinder under fluid loading

Effect of fluid and driving pressure on cyclical “on–off” flow of pulmonary microcirculation during mechanical ventilation

ObjectivesThis study aimed to identify the cyclical “on–off” flow of pulmonary microcirculation during inspiration and expiration by sidestream dark field imaging (SDF) technology in vivo and investigate the effects of volume status and driving pressure on cyclical “on–off” flow of microcirculation.Methods24 ARDS-modeled rabbits were randomly divided into high-driving pressure group (HDP group) and low-driving pressure group (LDP group). Lung microcirculation measurements were performed using the SDF microscope at two timepoints (T1 CVP 2–4 mmHg, T2 CVP 8–10 mmHg). From T1 to T2, 10 ml/kg saline was infused to increase CVP. The cyclical “on–off” pulmonary microcirculation was quantitatively assessed by the change of microcirculation between expiration and inspiration.ResultsProportion of perfused vessels (PPV), microvascular flow index (MFI), perfused vessel density (PVD), and total vessel density (TVD) at expiration were significantly higher than inspiration in the HDP group. The HDP group has a higher ΔPPV and ΔPVD. After fluid loading, ΔPPV and ΔMFI decreased. TNF-α, IL-6, Ang-2, and vWF levels in the HDP group were higher. The HDP group also has a higher lung wet-weight/body weight ratio, lung wet-to-dry weight ratio, and more severe damage of pulmonary capillaries than the LDP group.ConclusionsThe difference in alveolar perfused microcirculation between inspiration and expiration defined as cyclical “on–off flow” can be detected. High driving pressure can enhance the cyclical “on–off” flow, and fluid loading can relieve it. High driving pressure can potentially cause injury to pulmonary capillaries due to the phenomenon of “on–off” flow, thereby exacerbating ARDS.

Prevalence and timing of prenatal ultrasound findings in cytomegalovirus‐infected pregnancies

AbstractIntroductionTo investigate the prevalence and timing of prenatal neurosonographic abnormalities after primary cytomegalovirus seroconversion by the first trimester of pregnancy. The additional value of magnetic resonance imaging (MRI) and the correlation between cytomegalovirus viral load in amniotic fluid and adverse neonatal outcomes were evaluated.Material and MethodsA retrospective study between 2006 and 2022 examined data from 440 women with amniocentesis for periconceptional and first‐trimester cytomegalovirus seroconversion. Cases with positive amniocentesis and subsequent follow‐up were included. Prenatal neurosonography, MRI, and clinical outcomes were analyzed.ResultsOut of 190 women included, 37% (n = 70) presented with a normal neurosonography. Patients exhibiting abnormal neurosonography findings showed higher viral loads in amniotic fluid compared to those with a normal neurosonography (p = 0.002). In 26% (n = 49) the first abnormal ultrasound sign was already picked up at amniocentesis, and the most common ones were echogenic bowels (49%) and periventricular echogenicity (43%). With increasing gestational age, the likelihood of a new abnormal neurosonography finding decreases. MRI discovered additional abnormalities in 14% (n = 10).ConclusionsThe results highlight the importance of combining diagnostic modalities, from amniocentesis to biweekly ultrasound monitoring and subsequent MRI evaluation, to capture the chronological progression and subsequent outcome of congenital cytomegalovirus.

Investigation on the characteristics of flow-induced vibration and noise of acoustic window with embedded compound acoustic black holes

In recent decades, acoustic black hole (ABH) structures have shown significant potential for suppressing structural vibrations and noise radiation. However, the ABH structure has not been applied to panel–cavity noise control under heavy fluid loading. In this study, a hybrid numerical approach was used to analyse the vibro-acoustic response suppression mechanism of a compound acoustic black hole (CABH) acoustic window under turbulent boundary layer (TBL) excitation. Both sides of the acoustic window interact with the water. The results show that the local vibration modes of the CABH lead to a strong interaction between the structure and damping material. The amplitude of the high-order modal wavenumber spectra of the CABH was small, which weakened the spatial coupling between the TBL pressure and the structure. The coupling strength between the CABH acoustic window and the internal sound field was reduced, causing noise suppression inside the cavity. To further examine the noise reduction performance of the CABH panel cavity system, a flow-induced experiment with a large-scale CABH acoustic window was carried out in a large cavitation channel, and the results showed significant hydrodynamic self-noise reduction.

Calculation and analysis of wet clutch sliding torque based on fluid-solid coupling dynamic behavior

The fluid dynamics equations of groove cavity and non-grooved gap are established and combined to obtain fluid load bearing model. Considering the chain effect among local deformation, the deformation equation of friction surface under fluid-solid coupling load is developed to characterize reconstructed friction gap. The internal pressure and external load are used to iteratively solve the distribution of film thickness and contact area. An improved sliding torque calculation model is established by the microscopic state of fluid motion and solid deformation instead of fitting friction coefficient by multiple conditions. The accuracy of torque model is proved by sliding test. The influence of applied pressure, relative speed and lubricant flow on torque is weakened in turn according to fluid-solid state analysis.

Standardization of transthoracic impedance values for estimating heart failure and its utility

Abstract Background The use of intrathoracic impedance for examining pleural effusion in heart failure patients has been explored previously. However, due to concerns about its accuracy and complexity, transthoracic impedance values have had limitations in quantifying extravascular lung water. Our dual objectives were to clarify the relationship between intrathoracic conditions and percutaneous transthoracic impedance values, and to establish a basic model for a new machine learning-based estimation system for assessing intrathoracic conditions in patients with heart failure. Methods First, we developed a live porcine congested lung model that induced pleural effusion by substantial fluid loading, and then longitudinally evaluated its correlation with percutaneous transthoracic impedance values. Second, we conducted multi-frequency bioelectrical impedance analysis to simultaneously collect electrical, physical, and hematological data from 63 hospitalized heart failure patients and 82 healthy volunteers Results In the porcine model, pleural effusion correlated with a concurrent decrease in SpO2 and a gradual decrease in impedance. We indexed and generated features from the measured values and developed an intrathoracic estimation model based on electrical measurements and clinical findings using a decision tree-based machine learning approach. Among the 286 features collected per individual, the model used 16 features. Notably, the model demonstrated high accuracy in discriminating patients with pleural effusion, achieving an AUC of 0.905 (95% CI: 0.870-0.940) in cross-validation, significantly outperforming the conventional frequency-based method. Conclusions Transthoracic impedance values, when indexed, reflect intrathoracic conditions and improve estimation. Our results highlighted the potential of machine learning and thoracic impedance measurement for accurate estimation of pleural effusion. This approach provides an effective means of assessing intrathoracic conditions. Figure: The upper figure shows the relationship between impedance values and pleural effusion in the congested lung model. On these results, human data were collected to construct the estimation model. The lower illustrates the accuracy of the model and provides a comprehensive view of the system.

Antimicrobial activity of ceftibuten/polymyxin B combination against polymyxin/carbapenem-resistant Klebsiella pneumoniae.

To evaluate the synergistic effect of a ceftibuten and polymyxin B combination and to determine its capacity to overcome polymyxin B resistance in polymyxin/carbapenem-resistant (PC-R) Klebsiella pneumoniae. To investigate the combination's antibacterial efficacy, antimicrobial susceptibility tests using broth microdilution methods, chequerboard assays and time-kill testing were performed. Antibiofilm activity was also assessed. The treatment's effect on the bacterial cell membrane was examined by quantifying intracellular protein leakage and conducting scanning electron microscopy. Haemocompatibility tests were conducted to evaluate toxicity. Additionally, an infection model was established using Swiss mice to assess in vivo antimicrobial activity. The ceftibuten/polymyxin B combination demonstrated synergistic effects against several PC-R strains of K. pneumoniae, as determined by the FIC index (FICI) values, which ranged from 0.15 to 0.37. This combination was efficacious, exhibiting bactericidal activity at twice the MIC. Ceftibuten/polymyxin B also demonstrated antibiofilm activity. Additionally, ceftibuten/polymyxin B neither damaged the bacterial membrane nor exhibited haemolytic activity. Based on these findings, the in vivo therapeutic potential was investigated and it was found that ceftibuten/polymyxin B significantly decreased the bacterial load in the peritoneal lavage fluid of mice, revealing its effectiveness in treating infections caused by PC-R K. pneumoniae. The ceftibuten/polymyxin B combination exhibited synergistic effects in vitro and in vivo, and thus might be a promising therapeutic alternative for treating PC-R K. pneumoniae infections. As the combination was efficacious in preclinical models, researchers may further investigate its potential in clinical studies.

Experimental and numerical analysis of the fluid flow behavior of a tank corner impacting a water surface

The interaction of a tank impacting a water surface is an extremely complex nonlinear multiphase flow phenomenon. In this study, experiments and numerical simulations are used to systematically investigate the flow physics and load characteristics of a tank corner impacting a water surface. Free surface flow at different fall heights (200–800 mm) and inclination angles (0°–15°) was obtained through free fall experiments. The volume of fluids method and overset grid technology were used to simulate the water impact process of a three-dimensional structure accurately. For typical bubble flows, the numerical and experimental results agree well. On the basis of the three-dimensional flow characteristics and pressure distribution, flow behaviors, such as fluid climbing, corrugation disturbances, and air cavity effects, are analyzed. Bubble flow has a significant effect on the behavior mode of the impact load. In particular, the bubbles at the upper wall play a key role in the load characteristics at different locations. In addition, the influences of corrugations inside the tank's corner and the impact velocity on fluid flow were investigated. These results provide beneficial references for an in-depth understanding of the fluid flow and load characteristics between a tank and fluid.

Mass conservation in the validation of fluid-poroelastic structure interaction solvers

Benchmark problems commonly used to test numerical methods for fluid-poroelastic structure interaction often rely on simple examples constructed using the method of manufactured solutions. In this work, we show that such examples are not adequate to demonstrate the performance of the method, especially in cases when the poroelastic system is written in the primal or primal-mixed formulation, and when the dynamics of the poroelastic structure are driven only by dynamic loading from the fluid, which often occurs in biomedical applications. In those cases, the only forcing on the structure comes from the interaction with the fluid at the fluid-structure interface, where the coupling conditions are imposed. One of those conditions is a kinematic condition which enforces the conservation of mass. If this condition is not accurately satisfied, the resulting dynamics might lead to highly inaccurate results in the entire domain. We present three benchmark problems: Example 1 is based on the method of manufactured solutions; Example 2 is based on parameters used in geomechanics; and Example 3 is a benchmark problem with parameters from hemodynamics. Using these examples, we test the performance of the primal, primal-mixed and dual-mixed formulations. While all methods perform well in the first two examples, the primal and primal-mixed formulations exhibit large errors in Example 3, where the densities of the fluid and solid are comparable, and the structure dynamics is purely driven by the fluid loading. To recover the accuracy, we propose to use the primal and primal-mixed methods with a penalty term, which helps to enforce the conservation of mass.

Synovial fluid does not retard fluid exudation during stress-relaxation of immature bovine cartilage

Interstitial fluid load support (FLS) is a dominant mechanism of lubrication in cartilage, producing a low friction coefficient while enhancing the tissue’s load bearing capabilities. Due to its viscosity, synovial fluid (SF) may retard loss of FLS by slowing the exudation of interstitial fluid from the cartilage. This study tested this hypothesis by comparing the stress-relaxation (SRL) response of immature bovine articular cartilage immersed either in phosphate buffered saline (PBS) or in healthy mature bovine SF, under unconfined compression (fluid exudation across cut lateral tissue boundary) and indentation testing (fluid exudation across articular surface). To investigate the influence of diffusion of SF molecular constituents into cartilage, the effect of incubation time in SF on SRL was also investigated. The SRL response in unconfined compression was not significantly different in PBS versus SF when compared directly (p = 0.98) and had a slope ofm = 1.00 ± 0.04 (R2 = 0.989 ± 0.007). Samples tested in PBS exhibited characteristic relaxation times, τPBS=42.6 ± 5.3 s andτSF = 40.8 ± 4.7 s, that were not significantly different (p = 0.40). Incubation time of 24 h in SF resulted in no significant difference in the SRL response (p = 0.39, m=1.03 ± 0.12; R2=0.983 ± 0.011, andτPBS = 43.4 ± 10.7 s versusτSF = 41.5 ± 4.8 s, p = 0.59). Indentation testing showed some statistically significant, but functionally insignificant, difference in SRL responses in PBS versus SF with a slope ofm = 0.958 ± 0.060 (R2 = 0.957 ± 0.020, p = 0.029, andτPBS = 16.9 ± 2.6 s versusτSF = 19.4 ± 3.3 s, p = 0.073). Based on these results, we reject the hypothesis that healthy SF can retard the loss of FLS in cartilage due to its viscosity.

6-Methoxyldihydrochelerythrine Chloride Inhibiting Intra and Extracellular Drug-Resistant Bacteria.

Vancomycin-resistant enterococcus (VRE) is a major nosocomial pathogen that exhibits enhanced infectivity due to its robust virulence and biofilm-forming capabilities. In this study, 6-methoxyldihydrochelerythrine chloride (6-MDC) inhibited the growth of exponential-phase VRE and restored VRE's sensitivity to vancomycin. 6-MDC predominantly suppressed the de novo biosynthetic pathway of pyrimidine and purine in VRE by the RNA-Seq analysis, resulting in obstructed DNA synthesis, which subsequently weakened bacterial virulence and impeded intracellular survival. Furthermore, 6-MDC inhibited biofilm formation, eradicated established biofilms, reduced virulence, and enhanced the host immune response to prevent intracellular survival and replication of VRE. Finally, 6-MDC reduced the VRE load in peritoneal fluid and cells significantly in a murine peritoneal infection model. This paper provides insight into the potential antimicrobial target of benzophenanthridine alkaloids for the first time.

An experimental study of a quasi-impulsive backwards wave force associated with the secondary load cycle on a vertical cylinder

Steep wave breaking on a vertical cylinder (a typical foundation supporting offshore wind turbines) will induce slam loads. Many questions on the important violent wave loading and the associated secondary load cycle remain unanswered. We use laboratory experiments with unidirectional waves to investigate the fluid loading on vertical cylinders. We use a novel three-phase decomposition approach that allows us to separate different types of nonlinearity. Our findings reveal the existence of an additional quasi-impulsive loading component that is associated with the secondary load cycle and occurs in the backwards direction against that of the incoming waves. This quasi-impulsive force occurs at the end of the secondary load cycle and close to the passage of the downward zero-crossing point of the undisturbed wave. Wavelet analysis showed that the impulsive force exhibits superficially similar behaviour to a typical wave-slamming event but in the reverse direction. To monitor the scattered wave field and extract run-up on the cylinder, we installed a four-camera synchronised video system and found a strong temporal correlation between the arrival time of the Type-II scattered wave onto the cylinder and the occurrence of this quasi-impulsive force. The temporal characteristics of this quasi-impulsive force can be approximated by the Goda wave impact model, taking the collision of the Type-II scattered waves at the rear stagnation point as the impact source.

Mechanism of KLF2 in young mice with pneumonia induced by Streptococcus pneumoniae

BackgroundStreptococcus pneumoniae (Spn) is a major causative agent of pneumonia, which can disseminate to the bloodstream and brain. Pneumonia remains a leading cause of death among children aged 1–59 months worldwide. This study aims to investigate the role of Kruppel-like factor 2 (KLF2) in lung injury caused by Spn in young mice.MethodsYoung mice were infected with Spn to induce pneumonia, and the bacterial load in the bronchoalveolar lavage fluid was quantified. KLF2 expression in lung tissues was analyzed using real-time quantitative polymerase chain reaction and Western blotting assays. Following KLF2 overexpression, lung tissues were assessed for lung wet-to-dry weight ratio and Myeloperoxidase activity. The effects of KLF2 on lung injury and inflammation were evaluated through hematoxylin and eosin staining and enzyme-linked immunosorbent assay. Chromatin immunoprecipitation and dual-luciferase assay were conducted to examine the binding of KLF2 to the promoter of microRNA (miR)-222-3p and cyclin-dependent kinase inhibitor 1B (CDKN1B), as well as the binding of miR-222-3p to CDKN1B. Levels of miR-222-3p and CDKN1B in lung tissues were also determined.ResultsIn young mice with pneumonia, KLF2 and CDKN1B were downregulated, while miR-222-3p was upregulated in lung tissues. Overexpression of KLF2 reduced lung injury and inflammation, evidenced by decreased bacterial load, reduced lung injury, and lower levels of proinflammatory factors. Co-transfection of miR-222-3p-WT and oe-KLF2 significantly reduced luciferase activity, suggesting that KLF2 binds to the promoter of miR-222-3p and suppresses its expression. Transfection of CDKN1B-WT with miR-222-3p mimics significantly reduced luciferase activity, indicating that miR-222-3p binds to CDKN1B and downregulates its expression. Overexpression of miR-222-3p or downregulation of CDKN1B increased bacterial load in BALF, lung wet/dry weight ratio, MPO activity, and inflammation, thereby reversing the protective effect of KLF2 overexpression on lung injury in young mice with pneumonia.ConclusionsKLF2 alleviates lung injury in young mice with Spn-induced pneumonia by transcriptional regulation of the miR-222-3p/CDKN1B axis.

Influence of interstitial fluid pressure, porosity, loading magnitude, and anisotropy in cortical bone adaptation

Adaptive elasticity in cortical bone has traditionally been modeled using Strain Energy Density (SED). Recent studies have highlighted the importance of interstitial fluid in bone adaptation, yet no research has quantified the role of interstitial fluid pressure and its effects, specifically incorporating both SED and interstitial fluid pressure in the adaptation process. This study introduces a novel formulation combining theory of porous media and theory of adaptive elasticity that considers both SED and interstitial fluid’s pressure in cortical bone adaptation. The formulation is solved using ANSYS Fluent and a MATLAB script, and sensitivity analyses were conducted, analyzing various porosities, loading magnitudes, anisotropic properties of cortical bone, and involvement coefficients of interstitial fluid’s pressure. This study reveals that bones with different vascular porosities (PV) tend to achieve similar density distributions under uniform loading over time. This highlights the significant role of interstitial fluid pressure in accelerating the convergence to optimal bone properties, especially in specimens with larger PV porosities. The findings emphasize the importance of fluid pressure in bone remodeling, aligning with previous studies. Furthermore, this study demonstrates that considering transversely isotropic material properties can significantly alter the remodeling configuration compared to isotropic material properties. This highlights the importance of accurately representing the anisotropic nature of cortical bone in models to better predict its adaptive responses. However, aspects such as fluid density variations and bone geometry changes remain unexplored, suggesting directions for future research. Overall, this research enhances the understanding of cortical bone adaptation and its mechanical interactions.

Определение вязкости и диэлектрической проницаемости жидкости методом эквивалентных схем с помощью резонатора с поперечным электрическим полем

The paper presents a method for determining the viscosity and permittivity of a liquid using the equivalent circuit method. The parameters of the Mason equivalent circuit were found for a piezoelectric resonator with a lateral electric field made of PZT-19 ceramics. The frequency dependences of the real and imaginary parts of the electrical impedance of a resonator loaded with liquid samples with different viscosity and permittivity were measured. The fitting of the theoretical frequency dependences of the real and imaginary parts of the electrical impedance of a resonator loaded with mixtures of “water - isopropyl alcohol” and “water - glycerin” to the measured dependences was carried out. As the result the dependence of the permittivity of the liquid on the additional capacitance (determined from the Mason scheme) and the dependence of the shear fluid viscosity on the imaginary part of the mechanical impedance of the fluid load (determined from the Mason scheme) were built. These dependences can be used as calibration curves to determine dielectric constant and viscosity.

Use of the cardiac power index to predict fluid responsiveness in the prone position: a proof-of-concept study

BackgroundThe primary aim of this proof-of-concept study was to investigate whether the Cardiac Power Index (CPI) could be a novel alternative method to assess fluid responsiveness in the prone position. MethodsPatients undergoing scheduled elective lumbar spine surgery in the prone position under general anesthesia were enrolled in the criteria of patients aged 19–75 years with American Society of Anesthesiologists (ASA) physical status I–II. The hemodynamic variables were evaluated before and after changes in posture after administering a colloid bolus (5 mL.kg−1) in the prone position. Fluid responsiveness was defined as an increase in the Stroke Volume Index (SVI) ≥ 10%. ResultsA total of 28 patients were enrolled. In responders, the CPI (median [1/4Q–3/4Q]) decreased to 0.34 [0.28–0.39] W.m−2 (p = 0.035) after the prone position. After following fluid loading, CPI increased to 0.48 [0.37–0.52] W.m−2 (p < 0.008), and decreased SVI (median [1/4Q–3/4Q]) after prone increased from 26.0 [24.5–28.0] mL.m−2 to 33.0 [31.0–37.5] mL.m−2 (p = 0.014). Among non-responders, CPI decreased to 0.43 [0.28–0.53] W.m−2 (p = 0.011), and SVI decreased to 29.0 [23.5–34.8] mL.m−2 (p < 0.009). CPI exhibited predictive capabilities for fluid responsiveness as a receiver operating characteristic curve of 0.78 [95% Confidence Interval, 0.60–0.95; p = 0.025]. ConclusionThis study suggests the potential of CPI as an alternative method to existing preload indices in assessing fluid responsiveness in clinical scenarios, offering potential benefits for responders and non-responders.

Numerical investigation into effects of slot control on flow around wind turbine blades

This paper investigates the effects of slots on wind turbine blade sections on the reduction of fluid loads on the airfoil in turbulent flows. The governing conversation equations were discretized using the finite volume method (FVM), numerically simulating an unsteady flow with a turbulent regime. It was found that slots at ΨA70° and high angles of attack (AOAs) improved the aerodynamic performance of the airfoil and delayed the stall by 2°. The Cl-Cd ratio was 31.49%, 79.22%, and 29.66% higher in the slotted airfoil than in the non-slotted one at an AOA of 18°, 20°, and 22°, respectively. Furthermore, slots with ΨA70° at AOAs of 20° and 22° substantially reduced lift and drag variations on the airfoil.

Therapeutic impact of basic critical care echocardiography performed by residents after limited training

BackgroundThe objective was to assess the agreement between therapeutic proposals derived from basic critical care echocardiography performed by novice operators in ultrasonography after a limited training (residents) and by experts considered as reference. Secondary objectives were to assess the agreement between operators’ answers to simple clinical questions and the concordance between basic two-dimensional measurements.MethodsThis observational, prospective, single-center study was conducted over a 3-year period in a medical-surgical intensive care unit. Adult patients with acute circulatory and/or respiratory failure requiring a transthoracic echocardiography (TTE) examination were studied. In each patient, a TTE was performed by a resident novice in ultrasonography after a short training program and by an expert, independently but within 1 h and in random order. Each operator addressed standardized simple clinical questions and subsequently proposed a therapeutic strategy based on a predefined algorithm.ResultsResidents performed an average of 33 TTE studies in 244 patients (156 men; age: 63 years [52–74]; SAPS2: 45 [34–59]; 182 (75%) mechanically ventilated). Agreement between the therapeutic proposals of residents and experienced operators was good-to-excellent. The concordance was excellent for suggesting fluid loading, inotrope or vasopressor support (all Kappa values > 0.80). Inter-observer agreement was only moderate when considering the indication of negative fluid balance (Kappa: 0.65; 95% CI 0.50–0.80), since residents proposed diuretics in 23 patients (9.5%) while their counterparts had the same suggestion in 35 patients (14.4%). Overall agreement of responses to simple clinical questions was also good-to-excellent. Intraclass correlation coefficient exceeded 0.75 for measurement of ventricular and inferior vena cava size.ConclusionsA limited training program aiming at acquiring the basic level in critical care echocardiography enables ICU residents novice in ultrasonography to propose therapeutic interventions with a good-to-excellent agreement with experienced operators.