Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

ASSESSMENT OF CFD CODES CAPABILITIES TO PREDICT THE RISK OF FLAMMABILITY OR EXPLOSIVITY IN THE EVENT OF A HYDROGEN LEAK IN NUCLEAR FACILITIES

International audienceIn the context of nuclear safety, a 4 m3 experimental ventilated enclosure called CARDAMOMETTE has been implemented at IRSN to study the risk of explosion in the event of a hydrogen leakage from a duct in a nuclear facility. Different configurations of hydrogen leakage have been studied allowing to identify those that could potentially lead to explosivity conditions. For safety reason, helium was considered to simulate the behavior of hydrogen. Thanks to high level instrumentation (PIV, He mass spectrometry) and a well-equipped facility allowing local measurements inside the enclosure, a lot of data has been acquired, ensuring a very accurate validation of the CFD code ANSYS CFX. The objective of this validation is to evaluate the capabilities of the CFD code to predict the potential risk of explosivity depending on gas leakage and ventilation configurations.For this purpose, an experimental and numerical program has been launched to study the influence of ventilation (location of air inlets, renewal rates), gas leakage configurations (location and flowrate, impinging jet) and space clutter (cylindrical container, tubes network, suspended ceiling) on helium dispersion inside the experimental bench and to highlight those leading to hazardous situations.First, code-experiment comparisons of airflows inside the enclosure were led to ensure the capability of the CFD code to reproduce experimental airflows for some configurations. PIV velocity fields and experimental air renewal curves have been compared to those obtained with CFD calculations, showing a satisfactory agreement. Thanks to this first step, optimal numerical parameters (turbulence model, mesh, boundary conditions) have been chosen.Secondly, studies of helium dispersion were carried out according to the different configurations presented before. In this paper, only results for free helium jet and impinging helium jet on the wall are presented. Experimental and numerical results of local concentrations were compared, showing a very good agreement and hence the capability of the code to highlight the high concentration areas. Sensitivity studies about turbulent Schmidt number were also led, allowing to define the best numerical dataset depending on the helium injection configurations.Other experimental and numerical comparisons are currently in progress, especially for the configuration of an impinging helium jet on a cylindrical container

Experimental and numerical studies of gaseous and particulate pollutants backflow through an opening from a depressurized enclosure: application to nuclear dismantling operations

International audienceDuring nuclear maintenance and dismantling operations, a dynamic confinement due to inflow passing through openings is applied in order to prevent the leakage of pollutants from depressurized enclosures. This ensures better safety for operating people. To guaranty an efficient dynamic confinement, three values for the velocity of the inward flow near the opening were required in the past, depending on the dangerousness of the radioactive pollutants. Nowadays the ISO standard (ISO, 2004) advises to study every situation independently from the other (Lafanechere, 2009).However, some aeraulic environments induced by activities inside the enclosure (such as countercurrent blowing works facing the opening) could generate local and temporary flow reversals near the opening which would then lead to leaks of pollutants outward the enclosure. Preliminary laser visualizations (Figure 1) have shown that the presence of an additional countercurrent turbulent jet flow in competition with the mean inward flow is among the main causes of backflow through the opening. The main purposes of this work are to detect and measure experimentally the backflow of gaseous and particulate pollutants to outside the depressurized enclosure induced by a countercurrent jet. It aims also at verifying the ability of CFD (Computational Fluids Dynamics) simulations to predict these flow inversions near the opening by using SST-DES turbulent model. Experiments were performed on an enclosure with small opening (0.03 × 0.1) 〖cm〗^2 on its frontal wall. Gas and particles tracing techniques highlight and contribute to quantify the backflow phenomenon near the opening. Experimental results show that the behavior of the gaseous and particulate pollutants (aerosol of aerodynamic diameter 5 microns) is similar in terms of backflow magnitude near the opening. CFD results (Figure 2) confirmed the reliability of the hybrid model SST-DES to quantify the backflow phenomenon near the opening. This model has been successfully compared to experimental results on gaseous and particulate leakage.We found that in addition to the ISO recommendations on the inflow velocity at the opening, a new aeraulic criterion based on the disturbance and the inflow velocities ratio at the opening should be taken into account to ensure an efficient confinement. The perspectives of this work are to perform experiments on a real depressurized airlock, while varying the disturbance type (countercurrent or parietal jet, inside or outside the enclosure, disturbance related to the motion of an external obstacle..). Simultaneously, we aim to test the ability of numerical simulations to predict the backflow phenomenon at this scale

Experimental and numerical studies of gaseous and particulate pollutants backflow through an opening from a depressurized enclosure: application to nuclear dismantling operations

International audienceDuring nuclear maintenance and dismantling operations, a dynamic confinement due to inflow passing through openings is applied in order to prevent the leakage of pollutants from depressurized enclosures. This ensures better safety for operating people. To guaranty an efficient dynamic confinement, three values for the velocity of the inward flow near the opening were required in the past, depending on the dangerousness of the radioactive pollutants. Nowadays the ISO standard (ISO, 2004) advises to study every situation independently from the other (Lafanechere, 2009).However, some aeraulic environments induced by activities inside the enclosure (such as countercurrent blowing works facing the opening) could generate local and temporary flow reversals near the opening which would then lead to leaks of pollutants outward the enclosure. Preliminary laser visualizations (Figure 1) have shown that the presence of an additional countercurrent turbulent jet flow in competition with the mean inward flow is among the main causes of backflow through the opening. The main purposes of this work are to detect and measure experimentally the backflow of gaseous and particulate pollutants to outside the depressurized enclosure induced by a countercurrent jet. It aims also at verifying the ability of CFD (Computational Fluids Dynamics) simulations to predict these flow inversions near the opening by using SST-DES turbulent model. Experiments were performed on an enclosure with small opening (0.03 × 0.1) 〖cm〗^2 on its frontal wall. Gas and particles tracing techniques highlight and contribute to quantify the backflow phenomenon near the opening. Experimental results show that the behavior of the gaseous and particulate pollutants (aerosol of aerodynamic diameter 5 microns) is similar in terms of backflow magnitude near the opening. CFD results (Figure 2) confirmed the reliability of the hybrid model SST-DES to quantify the backflow phenomenon near the opening. This model has been successfully compared to experimental results on gaseous and particulate leakage.We found that in addition to the ISO recommendations on the inflow velocity at the opening, a new aeraulic criterion based on the disturbance and the inflow velocities ratio at the opening should be taken into account to ensure an efficient confinement. The perspectives of this work are to perform experiments on a real depressurized airlock, while varying the disturbance type (countercurrent or parietal jet, inside or outside the enclosure, disturbance related to the motion of an external obstacle..). Simultaneously, we aim to test the ability of numerical simulations to predict the backflow phenomenon at this scale

Experimental study of backflow air leakage through an opening from a depressurized enclosure

International audienceIn the nuclear decommissioning and dismantling operations, a dynamic confinement is applied to all openings in order to prevent the transfer of pollutants outside depressurized enclosures and to insure the safety of workers. To guaranty an efficient dynamic confinement, ISO 16647 and ISO 17873 standards recommend to maintain a constant value for the inward flow velocity near the opening depending on the level of radioactive pollution hazard. The main purpose of this work is to identify the possible conditions under which flow inversions near the opening may lead to gaseous pollutant leakage and then failure of the dynamic confinement. We aim at quantifying the amount of this pollutant backflow. The leakage from an experimental ventilated enclosure with a small opening on its frontal wall has been investigated. Laser flow visualizations and Particle Image Velocimetry (PIV) measurements showed that the presence of an additional turbulent jet flow in competition with the inward confinement flow is among the main causes leading to the leakage through the opening. The gas tracing technique has provided experimental data to quantify the pollutant backflow and allowed to compare the different scenarios. We conclude that a new criterion based on local aeraulic conditions near the opening is relevant to guaranty an efficient confinement

Contribution of IRSN R&D to reducing the risks of airborne pollutants dispersion during the dismantling of nuclear facilities

International audienceThis paper presents a general overview of IRSN research activities for assessing and reducing the risksof airborne dispersion of radioactive contamination during the dismantling operations of nuclearfacilities. Four main topic areas are addressed: aerosol source term, contamination transfers, behaviorof containment equipment and contamination metrology. Firstly, the various experimental and numericalmeans involved are presented

Moxifloxacin Efficacy and Vitreous Penetration in a Rabbit Model of Staphylococcus aureus Endophthalmitis and Effect on Gene Expression of Leucotoxins and Virulence Regulator Factors

Bacterial endophthalmitis is a serious complication of ocular surgery and of eye trauma; the leading causative organisms are Staphylococcus aureus strains. Tissue damage is due both to the host inflammatory response and to toxin synthesis by bacteria. Systemic treatment remains difficult because most antibiotics show poor ocular penetration. Moxifloxacin (MXF), a novel fluoroquinolone, was evaluated for its penetration into the vitreous of normal rabbit eyes and of eyes of rabbits infected for 24 h with methicillin-susceptible and methicillin-resistant S. aureus (MSSA and MRSA) following a single intravenous administration of 5 or 20 mg/kg. MXF penetration was rapid and efficient regardless of the dose, ranging from 28 to 52%. An inflammatory state of the vitreous significantly increased penetration after the 20-mg/kg dose, with penetration reaching 52%. Concentrations determined in the vitreous cavity following a 20-mg/kg administration showed a 3.5-fold decrease of the bacterial density within 5 h for MSSA (MIC, 0.125 μg/ml) and a 1.6-fold decrease for MRSA (MIC, 4 μg/ml) strains, respectively. By using a semiquantitative reverse transcription-PCR method, the expression of luk-PV and hlgCB, but not hlgA, encoding staphylococcal leukotoxins, was detected in the vitreous without MXF treatment. A slight decrease in the expression of leucotoxins and sarA, agr, and sigB virulence regulatory factors was observed 1 h following the administration of 5 mg of MXF per kg

LOW EXPOSURE TO SUNLIGHT IS A RISK FACTOR FOR CROHN'S DISEASE: CROHN'S DISEASE AND SUN EXPOSURE

International audienceBackground: Low sunshine exposure might contribute to IBD pathogenesis. Aim: To assess the geographic distribution of IBD incidence in relation to sunshine exposure in France, in order to test the hypothesis that higher sun exposure is associated with lower IBD risk. Methods: Using the national health insurance databases, incidence rates of CD and UC were estimated for each of 94 French administrative areas ("départements"), in 2000-2002. The surface UV radiation intensity was obtained by combining modeling and satellite data from Meteosat®, the European meteorological satellite. Relationships between incidence rates and sun exposure were tested for significance by using a Poisson regression. We mapped smoothed relative risks (sRR) for CD and UC, using a Bayesian approach and adjusting for sun exposure, in order to search for geographical variations. Results: Areas with a smoothed RR of CD incidence significantly above 1 corresponded to areas with low sunshine exposure, whereas those with high or medium sunlight exposure had smoothed RRs either lower than 1 or not significantly different from 1. There was no association between sun exposure and UC incidence. Conclusions: This geographic study suggests that low sunlight exposure is associated with an increased incidence of CD. Further studies are needed to determine if this association is causal

Expérience du soin des adolescents souffrant de troubles des conduites alimentaires: étude qualitative des professionnels de santé d'une unité psychiatrique adolescente et d'une unité pédiatrique adolescente

International audienceObjectives: The recommended treatment for Eating Disorders (EDs) is multidisciplinary and multimodal. Nonetheless, the complex linkage of the different disciplines involved is not necessarily simple. We analyzed the experience of healthcare professionals faced with psychiatric and psychological symptoms in adolescents with EDs in two “multidisciplinary” inpatient units embedded predominantly in different paradigms — one pediatric and one psychiatric. Methods: Qualitative analysis of 20 healthcare staff members’ interviews from different professional backgrounds working in inpatient units for EDs in Montreal (Canada) and Paris (France). Results: The “Complex patients” theme discusses the need for a global approach to the multiplicity of symptoms presented by these patients. “Management and its limits” describes the daily management of psychiatric symptoms in both units. “Psychiatry and Adolescent medicine: from opposition to collaboration” describes the different levels at which these disciplines work together and how this cooperation may be evolving. Conclusions: The complex entanglement intrinsic in EDs of the patients’ somatic, psychosocial, psychiatric, and adolescent problems requires collaboration between disciplines, but the modalities of this collaboration are multiple and evolve non-linearly in specialized treatment units. A multilevel approach must be offered, with the degree of collaboration (multidisciplinary, interdisciplinary and transdisciplinary) appropriate to the complexity of each adolescent's issues