Temporal changes in the epidemiology, management, and outcome from acute respiratory distress syndrome in European intensive care units: a comparison of two large cohorts

Background: Mortality rates for patients with ARDS remain high. We assessed temporal changes in the epidemiology and management of ARDS patients requiring invasive mechanical ventilation in European ICUs. We also investigated the association between ventilatory settings and outcome in these patients. Methods: This was a post hoc analysis of two cohorts of adult ICU patients admitted between May 1–15, 2002 (SOAP study, n = 3147), and May 8–18, 2012 (ICON audit, n = 4601 admitted to ICUs in the same 24 countries as the SOAP study). ARDS was defined retrospectively using the Berlin definitions. Values of tidal volume, PEEP, plateau pressure, and FiO2 corresponding to the most abnormal value of arterial PO2 were recorded prospectively every 24 h. In both studies, patients were followed for outcome until death, hospital discharge or for 60 days. Results: The frequency of ARDS requiring mechanical ventilation during the ICU stay was similar in SOAP and ICON (327[10.4%] vs. 494[10.7%], p = 0.793). The diagnosis of ARDS was established at a median of 3 (IQ: 1–7) days after admission in SOAP and 2 (1–6) days in ICON. Within 24 h of diagnosis, ARDS was mild in 244 (29.7%), moderate in 388 (47.3%), and severe in 189 (23.0%) patients. In patients with ARDS, tidal volumes were lower in the later (ICON) than in the earlier (SOAP) cohort. Plateau and driving pressures were also lower in ICON than in SOAP. ICU (134[41.1%] vs 179[36.9%]) and hospital (151[46.2%] vs 212[44.4%]) mortality rates in patients with ARDS were similar in SOAP and ICON. High plateau pressure (> 29 cmH2O) and driving pressure (> 14 cmH2O) on the first day of mechanical ventilation but not tidal volume (> 8 ml/kg predicted body weight [PBW]) were independently associated with a higher risk of in-hospital death. Conclusion: The frequency of and outcome from ARDS remained relatively stable between 2002 and 2012. Plateau pressure > 29 cmH2O and driving pressure > 14 cmH2O on the first day of mechanical ventilation but not tidal volume > 8 ml/kg PBW were independently associated with a higher risk of death. These data highlight the continued burden of ARDS and provide hypothesis-generating data for the design of future studies

Convergence de la méthode du point fixe modifiée ? pour le calcul de champ magnétique avec hystérésis

L'article présente une méthode itérative de type point fixe, pour calculer le champ magnétique dans un dispositif présentant de l'hystérésis magnétique. La méthode est appliquée à un calcul de champ bidimensionnel, par la méthode des éléments finis, dans lequel l'hystérésis est modélisé par un modèle scalaire analytique simple. La convergence du calcul est vérifiée. Un problème test élémentaire, qui ne converge pas par les méthodes habituelles, est résolu en potentiel magnétique scalaire d'une part, et en potentiel magnétique vecteur d'autre part. Les résultats prouvent l'efficacité de l'algorithme, appliqué à la modélisation d'un dispositif d'enregistrement magnétique

Investigation of soft magnetic material behavior under non symmetrical excitation

The paper presents a theoretical and experimental study of the behaviour of a FeSi80% magnetic alloy excited by a full rectified current. The experimental bench is described and the measured curve, called ΔB dynamic curve, is analysed using the dynamic Preisach model. A model including local and global dynamic effects is developed and a very close agreement with experimental data is found

Experimental analysis and multiscale modelling of the anisotropic mechanical and magnetostrictive behaviours of electrical steels

Non-Oriented (NO) iron-silicon laminations are commonly used in electrical engineering. Although these materials are assumed to exhibit a quasi-isotropic behaviour in the sheet plane, some specific coupled properties such as magnetostriction are very sensitive to a weak crystallographic texture. Magnetostriction is the strain mechanism that is induced by a magnetic field. This deformation contributes to the noise emitted by electrical machines. An experimental study of the process-induced anisotropy is presented, for both elastic and magnetostrictive behaviours. A multi-scale approach is then proposed, taking into account two sources of anisotropy: the usual cubic anisotropy at the grain scale, and the heterogeneous orientation of the grains (crystallographic texture) at the macro scale. It is shown that specific surface effects must be taken into account in the description of the anisotropy of industrial iron-silicon laminations

PROBLEM RELATED TO THE MBE GROWTH AT HIGH SUBSTRATE TEM0PERATURE FORGaAs-Ga1-xAlxAs DOUBLE HETEROSTRUCTURE LASERS

L'épitaxie par jets moléculaires à forte température du substrat(TS ≈ 600°C) est désormais de plus en plus utilisée pour obtenir des couchesde GaAs et Ga1-xAlxAs avec de bonnes propriétés électriques et optiques.Dans le cas des doubles hétérostructures lasers, l'optimisation du courant deseuil est obtenue en augmentant TS ; la valeur optimale que nous avons obtenueest de 1,5KA/cm2 une épaisseur de couche active de 0,16 µm. Cependantau-delà d'une valeur critique de TS d'environ 670°C, nous avons observé uneaugmentation de Js puis une disparition de l'émission laser. Cet effet estcorrelé à un problème particulier de la croissance MBE à très forte températurequi sera étudié.The MBE growth at high substrate temperature (TS ≈ 600°C) is now often used to obtain GaAs and Ga1-xAlxAs layers with improved electrical and optical properties. In the case of GaAs-Ga1-xAlxAs DH lasers, the optimisation of the threshold current density is obtained for increasing TS ; the ultimate value we reached is l,5KA/cm2 for an active layer thickness of 0,16µm However above a critical value of TS ≈ 670°C, an increase of Jth is observed until a non laser emission. This behaviour is related to a specific problem of MBE growth at extremely high substrate temperature, that will be described

RESPECTIVE ROLES OF IMPURITIES AND DEFECTS IN Al/Ga INTERDIFFUSION IN ION IMPLANTED GaAs-AlxGa1-xAs SUPERLATTICES

L'influence des défauts d'implantation, séparés des effets associés aux charges des impuretés, a été étudiée sur l'interdiffusion d'Al/Ga dans des superréseaux (SR) GaAs-Al0. 3Ga0.7As. L'implantation des éléments isoélectroniques 31P+ et 27Al+ ont été effectués dans des SR à deux températures (25°C et 250°C) dans le but d'obtenir différentes densités de défauts pour chaque élément. Les propriétés de ces structures, avant et après recuits à 850°C durant 6 h, ont été évaluées à l'aide de plusieurs techniques d'analyses. Ainsi, nous avons mis en évidence la dépendance d'interdiffusion sur la densité des défauts et la durée de leur recuit.The influence of implant damage, seperated from impurity change associated effects, has been investigated on Al/Ga interdiffusion. Implants of electrically inactive isoelectronic elements 31P+ and 27Al+ were performed in molecular beam epitaxy grown (MBE) GaAs-Al0.3Ga0.7As superlattices (SLs) at two distinct temperatures (25°C and 250°C) to generate different damage densities. Their properties, before and after anneals at 850°C for periods up to 6 h, were evaluated using several characterization techniques. An unambiguous evidence to the implant damage and anneal duration dependent Al/Ga interdiffusion is presented and discussed