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/)

Comportement thermomécanique d'un béton réfractaire : effets du renforcement par des fibres minérales

Adding fibres in concretes can modify their mechanical behaviour. Changes essentially depend on the geometry and on the composition of introduced fibres (metal, glasses, ceramics. . . ), on their volume fraction, on the requested temperature and on the thermomechanical behaviour of the reinforced material. The concrete is a damageable material with a brittle or quasi-brittle behaviour whose properties in direct tension are the weakest. Main objective of the fibre reinforcement is to improve the tension behaviour. Fibres can delay the damage localization phenomenon, can increase the material deformation capacity, can allow a resumption of load after cracking and can increase the peak stress level. These characteristics are also representative of the case of refractory concretes. However, the temperature plays a major role on their mechanical behaviour and microstructural evolutions. The aim of this study is to obtain a better understanding of the thermomechanical behaviour and of the microstructural evolutions of refractory concretes reinforced with mineral fibres. Thus mechanical tests and microstructure observations have been performed in a wide temperature range. Mechanical tests deal with tension tests and four point bending tests. Main microstructure observations have been done by scanning electron microscopy. Complementary results of mechanical tests and microstructural observations have made possible to interpret the behaviour of the reinforced refractory concretes, particularly in terms of reinforcement mechanisms up to 1200°C.Dans ce travail, un béton réfractaire silico-alumineux à base de granulats d'andalousite et à basse teneur en ciment a été renforcé par des fibres minérales. Elles appartiennent à deux grandes familles : les fibres de verre et les fibres à haute teneur en alumine. Le comportement thermomécanique du béton fibré a été caractérisé et analysé. Les mécanismes micromécaniques et microstructuraux qui pilotent ces comportements ont été identifiés. Ce travail a été fait d'une part à 20°C, en tenant compte de l'influence de la température de cuisson et d'autre part à haute température, après cuisson. Cette étude se base sur des résultats d'essais mécaniques jusqu'à 1 200°C, sur des observations microstructurales et sur la connaissance établie dans le domaine des bétons réfractaires non fibrés et fibrés mais également dans celui des bétons de génie civil fibrés. La démarche est basée sur l'établissement de relations entre la microstructure et le comportement thermomécanique, en considérant tout particulièrement l'endommagement aux basses températures ainsi que l'endommagement et la visco-plasticité aux hautes températures

Comportement thermomécanique d'un béton réfractaire (effets du renforcement par des fibres minérales)

TOULOUSE3-BU Sciences (315552104) / SudocALBI-ENSTIMAC (810042301) / SudocSudocFranceF

Comportement thermomécanique de bétons réfractaires : effet du renforcement par des fibres minérales

National audienc

Assessment of induction heated mould technologies for high-temperature thermoplastic composite manufacturing

The performances of Cage System® and 3iTech® moulds designed by Roctool for the thermo- compression moulding of high temperature composites have been investigated and compared to a conventional hot press equipped with cartridge heaters. The Cage System® technology demonstrated its capacity to achieve rapid temperature cycles with heating and cooling rates higher than 200°C.min-1, while allowing significant electricity energy saving. However, this heating technology induces critical thermal deformation of the moulding surfaces at high temperature. Advanced design is thus required for obtaining high thermal homogeneity and for satisfying dimensional accuracy of structural composites. As for the 3iTech® technology, the studied mould exhibited higher thermal performances than a conventional press with a heating rate up to 40°C.min-1 and a temperature homogeneity on the moulding surface lower than 10°C. Moreover, the carbon/PEEK laminate fabricated with this mould satisfied the dimensional tolerance for aerospace applications and therefore represent an interesting alternative to conventional heating systems

Ceramic Fibre Reinforced Refractory Castables for Very High Temperature Superplastic forming

International audienceno abstrac

Ceramic fibre reinforced refractory castables for very high temperature superplastic forming

Issu de : EuroSPF 2010 - 7th EuroSPF, San Sebastian, SPAIN, 8-10 September 2010International audienceIn the frame of the development of very high temperature die material solutions, two grades of alumina based ceramic fibres with a diameter close to 12 mu m have been investigated as reinforcement solutions for an andalusite refractory castable. High temperature mechanical tests were performed up to 1200 degrees C in four-point bending conditions: rupture tests at high temperature and anisothermal creep tests. After testing, microstructural and rupture surface were observed in order to get information on deformation mechanisms and rupture processes. Results show that significant mechanical improvement were obtained up to 1100 degrees C when compared to non reinforced refractory castables

Development and thermomechanical behavior of fiber reinforced refractory concretes.

International audienceno abstrac

Thermomechanical behaviour of refractory concretes : effect of a mineral fibre reinforcement

International audienc

Microstructural design and study of fibre reinforced refractory concretes

International audienc