Radiomic analysis of abdominal organs during sepsis of digestive origin in a French intensive care unit

Background Sepsis is a severe and common cause of admission to the intensive care unit (ICU). Radiomic analysis (RA) may predict organ failure and patient outcomes. The objective of this study was to assess a model of RA and to evaluate its performance in predicting in-ICU mortality and acute kidney injury (AKI) during abdominal sepsis. Methods This single-center, retrospective study included patients admitted to the ICU for abdominal sepsis. To predict in-ICU mortality or AKI, elastic net regularized logistic regression and the random forest algorithm were used in a five-fold cross-validation set repeated 10 times. Results Fifty-five patients were included. In-ICU mortality was 25.5%, and 76.4% of patients developed AKI. To predict in-ICU mortality, elastic net and random forest models, respectively, achieved areas under the curve (AUCs) of 0.48 (95% confidence interval [CI], 0.43–0.54) and 0.51 (95% CI, 0.46–0.57) and were not improved combined with Simplified Acute Physiology Score (SAPS) II. To predict AKI with RA, the AUC was 0.71 (95% CI, 0.66–0.77) for elastic net and 0.69 (95% CI, 0.64–0.74) for random forest, and these were improved combined with SAPS II, respectively; AUC of 0.94 (95% CI, 0.91–0.96) and 0.75 (95% CI, 0.70–0.80) for elastic net and random forest, respectively. Conclusions This study suggests that RA has poor predictive performance for in-ICU mortality but good predictive performance for AKI in patients with abdominal sepsis. A secondary validation cohort is needed to confirm these results and the assessed model

Relationship between positive end-expiratory pressure levels, central venous pressure, systemic inflammation and acute renal failure in critically ill ventilated COVID-19 patients: a monocenter retrospective study in France

Background The role of positive pressure ventilation, central venous pressure (CVP) and inflammation on the occurrence of acute kidney injury (AKI) have been poorly described in mechanically ventilated patient secondary to coronavirus disease 2019 (COVID-19). Methods This was a monocenter retrospective cohort study of consecutive ventilated COVID-19 patients admitted in a French surgical intensive care unit between March 2020 and July 2020. Worsening renal function (WRF) was defined as development of a new AKI or a persistent AKI during the 5 days after mechanical ventilation initiation. We studied the association between WRF and ventilatory parameters including positive end-expiratory pressure (PEEP), CVP, and leukocytes count. Results Fifty-seven patients were included, 12 (21%) presented WRF. Daily PEEP, 5 days mean PEEP and daily CVP values were not associated with occurrence of WRF. 5 days mean CVP was higher in the WRF group compared to patients without WRF (median [IQR], 12 mm Hg [11-13] vs. 10 mm Hg [9–12]; P=0.03). Multivariate models with adjustment on leukocytes and Simplified Acute Physiology Score (SAPS) II confirmed the association between CVP value and risk of WRF (odd ratio, 1.97; 95% confidence interval, 1.12–4.33). Leukocytes count was also associated with occurrence of WRF in the WRF group (14 G/L [11–18]) and the no-WRF group (9 G/L [8–11]) (P=0.002). Conclusions In mechanically ventilated COVID-19 patients, PEEP levels did not appear to influence occurrence of WRF. High CVP levels and leukocytes count are associated with risk of WRF

Modelling of the behavior of metallic foams under highly dynamic solicitations and application to shock wave mitigation

Les mousses métalliques ont connu un essor important durant les dernières décennies. Leur capacité à supporter de très larges niveaux de déformation tout en transmettant de faibles contraintes les rend particulièrement adaptés à des solutions d'absorption d'énergie ou de protection contre des sollicitations intenses.Le comportement dynamique de ce type de matériau peut être influencé par les effets inertiels au niveau des parois ou des ligaments constituant son squelette (micro-inertie). Un modèle de comportement à base micromécanique a été développé pour prendre en compte les effets micro-inertiels sur le comportement macroscopique de mousses à porosités fermées. Le modèle proposé repose sur la procédure d'homogénéisation dynamique introduite par Molinari et Mercier (2001). Par cette approche, les effets micro-inertiels apparaissent sous la forme d'un terme supplémentaire dans le tenseur des contraintes, appelé contrainte dynamique. À partir de comparaisons avec des données extraites de la littérature, il est ainsi démontré qu'inclure les effets micro-inertiels permet d'obtenir une meilleure description de la réponse des mousses sous choc.L'influence d'une épaisseur de mousse localisée entre un explosif et une enveloppe cylindrique a ensuite été étudiée en suivant deux approches. La première, qui s'appuie sur les travaux de Gurney (1943), repose sur des considérations énergétiques. La seconde méthode permet d'aboutir à une description plus détaillée des tailles et vitesses de fragments. Elle repose sur la combinaison d'un modèle éléments finis pour décrire la propagation de l'onde de choc dans la mousse et l'expansion de l'enveloppe et d'un modèle de fragmentation de type Mott (1947).Metallic foams have known a growing interest in the last decades. Their ability to undergo very large strains while transmitting only reasonable stress levels makes them particularly suitable for energy absorption applications and protection against intense solicitations. The dynamic behavior of metal foams is linked to inertial effects appearing at the walls and ligaments of the material microstructure (micro-inertia). A constitutive model has been developed to take micro-inertial effects into account when describing the macroscopic behavior of closed-cell foams submitted to dynamic loadings. The proposed approach was developed using the dynamic homogenization procedure introduced by Molinari and Mercier (2001). Within this framework, micro-inertial effects appear as an additional stress term, called dynamic stress. Comparisons with data from literature have showed that including micro-inertia effects allows one to achieve a better description of the foam response under shock loading.The influence of a foam layer placed between an explosive and a cylindrical casing has been investigated by following two approaches. The first one is based on energetic considerations, following the work of Gurney (1943). The second method allows one to obtain a more detailed description of fragment sizes and velocities. It relies on the combined use of a finite element model and a description of the shell fragmentation based on the work of Mott (1947)

Modelling of the behaviour of metal foams under shock compression

A theoretical modelling is proposed to describe the shock response of foam materials. This model is based on micromechanical and energetic arguments, and takes into account the contribution of microscale inertia. Within this framework, an analytical expression of the Hugoniot stress-strain curve is proposed for elastic-plastic cellular materials. The predictions derived from the proposed model are in excellent agreement with experimental data for open-cell aluminium foams. The case of viscoplastic foams is also considered

An analytical expression for the Hugoniot stress–strain curve of elastic-plastic cellular materials

CIFRE no 0843/2013International audienceThis note deals with the shock behaviour of foams and cellular solids. An analytical expression of the Hugoniot stress–strain curve has been developed using micromechanical and energetic arguments. In the case of elastic-plastic cellular materials, the application of the proposed formula is straightforward and the shock behaviour can be predicted from the quasi-static compressive response. Comparison of theoretical predictions with experimental results for open-cell aluminium foams shows an excellent agreement

Modelling of micro-inertia effects in closed-cell foams with application to acoustic and shock wave propagation

International audienceA continuum approach is proposed to describe micro-inertia effects in closed-cell foams using a micromechanical method. An initially spherical unit-cell was considered and the influence of inertia at the unit-cell level was characterised with the use of a dynamic homogenisation technique. The contribution of micro-inertia appears in the form of a dynamic component of the macroscopic stress. A closed-form expression of the dynamic stress was obtained. The proposed modelling was applied to acoustic and shock wave propagation. In both cases, the influence of micro-inertia was found to be significant. The obtained results are in good agreement with existing data of the literature, provided by micromechanically accurate finite element computations and experiments. The proposed model is aimed to enhance continuum models of foam materials by taking into account the contribution of micro-inertia