Sex difference and intra-operative tidal volume: Insights from the LAS VEGAS study

BACKGROUND: One key element of lung-protective ventilation is the use of a low tidal volume (VT). A sex difference in use of low tidal volume ventilation (LTVV) has been described in critically ill ICU patients.OBJECTIVES: The aim of this study was to determine whether a sex difference in use of LTVV also exists in operating room patients, and if present what factors drive this difference.DESIGN, PATIENTS AND SETTING: This is a posthoc analysis of LAS VEGAS, a 1-week worldwide observational study in adults requiring intra-operative ventilation during general anaesthesia for surgery in 146 hospitals in 29 countries.MAIN OUTCOME MEASURES: Women and men were compared with respect to use of LTVV, defined as VT of 8 ml kg-1 or less predicted bodyweight (PBW). A VT was deemed 'default' if the set VT was a round number. A mediation analysis assessed which factors may explain the sex difference in use of LTVV during intra-operative ventilation.RESULTS: This analysis includes 9864 patients, of whom 5425 (55%) were women. A default VT was often set, both in women and men; mode VT was 500 ml. Median [IQR] VT was higher in women than in men (8.6 [7.7 to 9.6] vs. 7.6 [6.8 to 8.4] ml kg-1 PBW, P < 0.001). Compared with men, women were twice as likely not to receive LTVV [68.8 vs. 36.0%; relative risk ratio 2.1 (95% CI 1.9 to 2.1), P < 0.001]. In the mediation analysis, patients' height and actual body weight (ABW) explained 81 and 18% of the sex difference in use of LTVV, respectively; it was not explained by the use of a default VT.CONCLUSION: In this worldwide cohort of patients receiving intra-operative ventilation during general anaesthesia for surgery, women received a higher VT than men during intra-operative ventilation. The risk for a female not to receive LTVV during surgery was double that of males. Height and ABW were the two mediators of the sex difference in use of LTVV.TRIAL REGISTRATION: The study was registered at Clinicaltrials.gov, NCT01601223

Dispersion and deposition of gas and aerosol particles in urban environment: examples of in situ experiments for predictive model validation

International audienceIn terms of chronic or accidental release of radioactive particles into the atmosphere, knowing atmospheric gas and particle dispersion, as well as particle-bound radionuclide deposition flux on ground surfaces is essential to assess risks on both populations and environments. Protecting urban environments and populations living in the vicinity is a major issue. However, urban areas are among the least studied environments due to their complexity in terms of dynamics, thermal properties and spatial heterogeneity. Our work focus on how in situ experiments help constraining predictive models of atmospheric gas and particle dispersion, and particle-bound radionuclide deposition flux on various spatiotemporal scales in urban environments. Examples of past and ongoing studies will be presented. Our in situ experiments use tracing gas (SF6 and He), tracing particles (fluorescein) or natural radionuclides already present in environment such as 7Be. Results will be discussed during the conference

Dispersion and deposition of gas and aerosol particles in urban environment: examples of in situ experiments for predictive model validation

International audienceIn terms of chronic or accidental release of radioactive particles into the atmosphere, knowing atmospheric gas and particle dispersion, as well as particle-bound radionuclide deposition flux on ground surfaces is essential to assess risks on both populations and environments. Protecting urban environments and populations living in the vicinity is a major issue. However, urban areas are among the least studied environments due to their complexity in terms of dynamics, thermal properties and spatial heterogeneity. Our work focus on how in situ experiments help constraining predictive models of atmospheric gas and particle dispersion, and particle-bound radionuclide deposition flux on various spatiotemporal scales in urban environments. Examples of past and ongoing studies will be presented. Our in situ experiments use tracing gas (SF6 and He), tracing particles (fluorescein) or natural radionuclides already present in environment such as 7Be. Results will be discussed during the conference

Aerosol Particle Dry Deposition Velocities above Grassland According to the Diameter and the Micrometeorological Parameters: The "V" Curve between 1.5 nm and 1 µm with Three Different Methods

Nuclear facilities introduce different types of radionuclides into the atmosphere in the form of gases and aerosols during chronic or accidental releases. These particles may be submitted to atmospheric dispersion, dry and wet deposition. The study of dry deposition based on the dry deposition velocity (dry deposition flux divided by an atmospheric concentration above the substrates) concept is a major issue concerning the impact of radionuclides on the population and the environment. Uncertainties on the dry deposition velocity values of submicronic particles are up to several orders of magnitude discrepancies according to the model used (Petroff et al., 2008). Moreover there is no data for particle diameter under 10 nm. So, the aim of this study is to quantify dry deposition velocity according the particles diameter and the atmospheric stability. Dry deposition flux can be determinate with different devices. We used 3 different methods to quantify the dry deposition velocities according the particles diameter. (1): For particles around 1.5 nm we studied the dry deposition of free faction of alpha particles of Rn222 decay products by the gradient method (2) For particles between 2.5 nm and 1.2 µm we used the eddy correlation method with a cospectral analysis (Pellerin et al., 2017): the dry deposition flux is determinate thanks to covariance between fluctuations of the vertical wind velocity and fluctuations of the atmospheric aerosol particle concentration during 30-minutes periods at high frequency. The aerosol particle concentration was measured by coupling two Condensation Particles Counters (CPC 3788, TSI, Inc.) for particle sizes between 2.5 and 14 nm (Twin CPC method) and for particle sizes between 7 nm and 1 µm, an Electrical Low Pressure Impactor (ELPI, Dekati, Inc.) was used. The wind 3-component velocity was measured by an ultrasonic anemometer (Young 81000, Inc.). (3) The last method used is the direct deposition of fluorescein particles of 0.6 µm on synthetic grass and the measurement are carrying on by a fluorimeter. Four experimental campaigns were conducted above a grassland in western France (near Poitiers) april 2015 and September 2016. The first results of these campaigns show that the particles under 10 nm are influenced only by the mechanical turbulence (link with the friction velocity u*), while the particles over 10 nm are influenced by the mechanical turbulence and the thermic turbulence (link with the sensible heat flux H). The different results of dry deposition velocities with the three different methods allowed to obtain a “V” curve between 1.5 nm and 1.2 µm. In fact, if we look the curve of dry deposition velocities normalized by friction velocities according to particles diameter and for the four sampling campaign, even if the used different technics, all of the point are consistent. Moreover we can find the theoretical curve shape of dry deposition velocity with the effects of the three dry deposition mechanisms: Brownian diffusion, interception and impaction. We propose to present the all used methods and devices and then, to describe the result

Iodine uptake in brown seaweed exposed to radioactive liquid discharges from the reprocessing plant of ORANO La Hague

International audienceIodine-129 is present in controlled liquid radioactive waste routinely released in seawater by the ORANO nuclear fuel reprocessing plant in La Hague (Normandy, France). Brown algae are known for their exceptional ability to concentrate iodine from seawater. They also potentially emit volatile iodine compounds in response to various stresses, such as during emersion at low tide. For these reasons, brown seaweed is routinely collected for radioactivity monitoring in the marine environment (Fucus serratus and Laminaria digitata). Despite the high concentration ratio, the exact mechanism of iodine uptake is still unclear. Chemical imaging by laser desorption/ionization mass spectrometry provided evidence that iodine is stored by kelps as I−. In this study we investigate in vivo iodine uptake in kelps (L. digitata) with an emphasis on seawater iodine chemical speciation. Our results showed that kelp plantlets were able to take up iodine in the forms of both IO3− and I−. We also observed transient net efflux of I− back to seawater but no IO3− efflux. Since the seaweed stores I− but takes up both IO3− and I−, IO3− was likely to be converted into I− at some point in the plantlet. One major outcome of our experiments was the direct observation of the kelp-based biogenic conversion of seawater IO3− into I−. On the basis of both IO3− and I− uptakes by the seaweed, we propose new steps in the possible iodine concentration mechanism used by brown algae

Mesures des vitesses de dépôt sec pour les particules atmosphériques de 1,5 nm à 1,2 µm : la courbe en "V"

National audienceTo assess the impact of an accidental or chronic radionuclide release in form of aerosol particles in the atmosphere, it is important to study their dry deposition above a grassland. Indeed, products derived from this environment are a component of the human food chain via livestock. For particles of less than 1 µm, there is a lack of experimental data in this regard, leading to uncertainty in terms of the results of models, which can reach up to two orders of magnitude. Moreover, there is no in situ deposition velocity measurement data available for particles that are smaller than 10 nm. These particles were formed by gas/particles reaction (nucleation) and may affect different radionuclides like iodine (129,131 I). The objective of this study is to measure and analyse the dry deposition velocity for aerosol particles with a particle size of between 1.5 nm and 1.2 µm, with particular focus on the particle size less than 10 nm. To this end, three different methods during 4 experimental campaigns were used above a grassland.Pour évaluer l'impact d'un rejet accidentel ou chronique sous forme de particules dans l'atmosphère, il est important d'étudier leur dépôt sec en milieu prairial. En effet, les produits issus de ce milieu sont une composante de la chaine alimentaire de l'homme via l'élevage. Pour les particules de moins de 1 μm, il y a un manque de données expérimentales, ce qui entraîne une incertitude sur les résultats des modèles, qui peuvent atteindre jusqu'à deux ordres de grandeur. En outre, il n'existe pas de données de mesure de la vitesse de dépôt in situ disponibles pour les particules inférieures à 10 nm. Ces particules sont issues de réaction gaz/particules (nucléation) et peuvent concerner certains radionucléides tels que l'iode (129,131 I). L'objectif de cette étude est de mesurer et de modéliser la vitesse de dépôt sec pour les particules avec une granulométrie comprise entre 1,5 nm et 1,2 μm, particulièrement la taille de particules inférieures à 10 nm. À cette fin, trois différentes méthodes expérimentales in situ ont été mises au point et utilisés durant 4 campagnes expérimentales au-dessus d'une prairie

Dissolved Radiotracers and Numerical Modeling in North European Continental Shelf Dispersion Studies (1982–2016): Databases, Methods and Applications

Significant amounts of anthropogenic radionuclides were introduced in ocean waters following nuclear atmospheric tests and development of the nuclear industry. Dispersion of artificial dissolved radionuclides has been extensively measured for decades over the North-European continental shelf. In this area, the radionuclide measurement and release fluxes databases provided here between 1982 and 2016 represent an exceptional opportunity to validate dispersion hydrodynamic models. This work gives accessibility to these data in a comprehensive database. The MARS hydrodynamic model has been applied at different scales to reproduce the measured dispersion in realistic conditions. Specific methods have been developed to obtain qualitative and quantitative results and perform model/measurement comparisons. Model validation concerns short to large scales with dedicated surveys following the dispersion: it was performed within a two- and three-dimensional framework and from minutes and hours following a release up to several years. Results are presented concerning the dispersion of radionuclides in marine systems deduced from standalone measurements, or according to model comparisons. It allows characterizing dispersion over the continental shelf, pathways, transit times, budgets and source terms. This review presents the main approaches developed and types of information derived from studies of artificial radiotracers using observations, hydrodynamic models or a combination of the two, based primarily on the new featured datasets

Measurement and modelling of gaseous elemental iodine (I2) dry deposition velocity on grass in the environment

International audienceAssessing the impact of radioactive iodine on humans subsequent to a nuclear accident requires a better understanding of its behaviour in the environment. An original approach aimed at developing a model constrained by data collected during experimental campaigns has been developed. These experimental campaigns, named MIOSEC 2 and MIOSEC 3 respectively, were conducted in the middle of grassland. They are based on emissions of gaseous elemental iodine (I2) into the atmosphere above the grassland to determine the dry deposition velocities of iodine on the grass and to model these velocities as a function of the environmental conditions, particularly wind friction velocity, sensible heat flux, and stomatal resistance. The measured dry deposition velocities were between 0.02 and 0.49 cm s-1 during MIOSEC 2, varying by more than one order of magnitude, and between 0.48 and 1.25 cm s−1 during MIOSEC 3. The dry deposition model for iodine developed as a result of these experiments relies on the micrometeorological characteristics of the atmospheric surface layer, the pertinent physical and chemical properties of the iodine and the surface properties of the grass; all these parameters were measured at the time of the experiments. Given the experimental conditions, the modelled dry deposition velocities varied between 0.11 and 0.51 cm s−1 during MIOSEC 2 and between 0.31 and 1.6 cm s−1 during MIOSEC 3. The dry deposition model for iodine indicates that the variations in deposition velocity are induced by the mechanical turbulence, since there is significant correlation between the dry deposition velocities of iodine and the wind friction velocities on grass. The model also shows that the higher deposition velocity values during MIOSEC 3 are due to the fact that the stomata were more open during the experiments. There is also significant correlation between the experimental results and modelled values both for MIOSEC 2 (R2 = 0.61) and for MIOSEC 3 (R2 = 0.71)

Transfer of Tritium Released into the Marine Environment by French Nuclear Facilities Bordering the English Channel

International audienceControlled amounts of liquid tritium are discharged as tritiated water (HTO) by the nuclear industry into the English Channel. Because the isotopic discrimination between 3H and H is small, organically bound tritium (OBT) and HTO should show the same T/H ratio under steady-state conditions. We report data collected from the environment in the English Channel. Tritium concentrations measured in seawater HTO, as well as in biota HTO and OBT, confirm that tritium transfers from HTO to OBT result in conservation of the T/H ratio (ca. 1 × 10 −16). The kinetics of the turnover of tritium between seawater HTO, biota HTO, and OBT was investigated. HTO in two algae and a mollusk is shown to exchange rapidly with seawater HTO. However, the overall tritium turnover between HTO and the whole-organism OBT is a slow process with a tritium biological half-life on the order of months. Nonsteady-state conditions exist where there are sharp changes in seawater HTO. As a consequence, for kinetic reasons, the T/H ratio in OBT may deviate transiently from that observed in HTO of samples from the marine ecosystem. Dynamic modeling is thus more realistic for predicting tritium transfers to biota OBT under nonsteady-state conditions

Tritium in precipitation on 5 sites in North-West France during the 2017–2019 period

International audienc