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/)

Linear stability of a vectorial kinetic relaxation scheme with a central velocity

International audienceThis article deals with the linear stability of an implicit vectorial kinetic relaxation scheme with a central velocity used to solve numerically some multi-scale hyperbolic systems

Linear stability of a vectorial kinetic relaxation scheme with a central velocity

International audienceThis article deals with the linear stability of an implicit vectorial kinetic relaxation scheme with a central velocity used to solve numerically some multi-scale hyperbolic systems

Does the Length of the Period Really Matter for the Identification and the Modelling of Monetary Policy Shocks?

In this Paper, we ask whether our empirical and theoretical knowledge about the effect of monetary policy shocks is robust to the choice of the period length. We think that such a question is particularly relevant in the monetary literature, as frictions are often introduced under the form of a one-period lag in agents’ reaction. We first show that it is possible to use more efficiently the available information when identifying monetary policy shocks. Using together quarterly series for GDP and monthly series for monetary aggregates and interest rates, it is possible to identify monetary shocks with the assumption that they do not have any impact on GDP within a month, by restricting ourselves to the identification of third-month-of-a-quarter shocks. With this new method, we obtain very similar estimated IRFs, as compared with the results obtained with quarterly data, although the price puzzle appears to be more pronounced in our estimates. Such a similarity is a new fact that quantitative models need to match. In the second part of the Paper, we propose a model-based explanation for this result, by computing a limited participation model predictions, when the time period is reduced from one quarter to one month, and when the model predictions are time-aggregated at the quarterly frequency. We show that the introduction of adjustment costs to portfolio reallocation into the model is not only improving its fit, but is necessary for obtaining qualitatively realistic predictions, when the length of the period is thought to be the month and not the quarter.limited participation; monetary policy shocks; time aggregation

Vectorial kinetic relaxation model with central velocity. Application to implicit relaxations schemes

International audienceWe apply flux vector splitting (FVS) strategy to the implicit kinetic schemes for hyperbolic systems. It enables to increase the accuracy of the method compared to classical kinetic schemes while still using large time steps compared to the characteristic speeds of the problem. The method also allows to tackle multi-scale problems, such asthelow Machnumber limit, for which wavespeeds with larger atioare involved. We present several possible kinetic relaxation schemes based on FVS and compare them on one-dimensional test-cases. We discuss stability issues for this kind of metho

Study of Physics-Based preconditioning with High-order Galerkin discretization for hyperbolic wave problems

In this article, we detail the construction of a physics-based preconditioner. The Schur decomposition is the key point of the method which is tested on two hyperbolic systems : acoustic wave equations and shallow water equations without source term. Some conserved properties between preconditoner and initial operator are discussed, especially the propagation speeds of a plane wave

Study of Physics-Based preconditioning with High-order Galerkin discretization for hyperbolic wave problems

In this article, we detail the construction of a physics-based preconditioner. The Schur decomposition is the key point of the method which is tested on two hyperbolic systems : acoustic wave equations and shallow water equations without source term. Some conserved properties between preconditoner and initial operator are discussed, especially the propagation speeds of a plane wave