Hydropeaking generates significant fluctuations in flow in downstream river reaches, resulting in frequent and major changes in the physical conditions of the fish habitat. The microhabitat methodology, derived from the IFIM, focuses on minimum flow studies in by‐pass sections, but has been adapted to two rivers subject to daily flow fluctuations (Ance du Nord and Oriège). Application of this methodology to hydropeaking conditions requires additional habitat descriptors to take into account the temporal aspects of peaking flows and their effects on trout habitat, i.e. flow and habitat chronologies analysed in duration and frequency. Hydropeaking and the natural upstream flow regime were compared. The results show that habitat variations are closely related to the flow regime and site morphology; hydropeaking effects on habitat parameters are different in wide and in deep profiles. It is suggested that, in both instances, hydraulic refugia are crucial for organisms to withstand the variations of physical variables. This approach helps in better understanding the physical limiting factors in situations of short‐term flow fluctuations.

In an experimental stream containing available refuge zones, moderate and instantaneous flow variations did not cause high mortality or substantial increase in downstream migration of 2‐month‐old grayling, Thymallus thymallus L. Fish were able to react rapidly to spate simulations by a change in space utilization determined by changes in water velocity patterns. Reaction of fish to these experimental flow variations corresponded to a refuge strategy, i.e. seeking shelter and minimizing the distance to find it.

Hydropower generation induces rapid and frequent fluctuations of hydrodynamic parameters in rivers downstream of hydroelectric impoundments. On the Fontauliere river (Ardeche basin, France , water releases come from the Loire basin and the flow varies from 1.3 to 20m3/s for one reach and from 0.1 to 20m /s for another reach. A reference site upstream was chosen to compare the communities with two downstream impacted sites. These two sites enabled two different base flow situations to be studied simultaneously and also the effect of base flow enhancement at one site. Benthic and epilithic samples were collected at the three sites on three dates. Epilithon development was linked to hydraulic regimes, with a major increase in algal biomass, dominated by filamentous algae, linked to the minimum base flow level and to the duration of periods without peaks. The macroinvertebrate communities of impacted reaches were less diversified and more specialized, with predominance of one or two taxa, whereas communities in upstream reaches were more diverse. The different morphological units specificity was attenuated in hydropeaking situations. In the case of a very low base flow, the lentic units with very low velocities (less than 4cms-') had different fauna. The downstream algal development explained part of the change in benthic community structure in trophic groups (i.e. dominance of scrapers) in the site with the higher base flow. When the base flow was too low, a trophic discordance was observed and excess algal biomass represented a limiting factor. Thus, this study indicated that base flow level and duration had important effects on epilithic development and on invertebrate trophic structure in terms of mean velocities and of number of days without peaks. J supplies from Montpezat power plant 3 reservoirs VEYRIERES DAM Peak Row = 20 mWs Micm-power p l a a g * _ * SITE3 Peak Row = 13 to 20 m3/s Base Row = 0.12 m3/s

The growing coronavirus disease (COVID-19) crisis has stressed worldwide healthcare systems probably as never before, requiring a tremendous increase of the capacity of intensive care units to handle the sharp rise of patients in critical situation. Since the dominant respiratory feature of COVID-19 is worsening arterial hypoxemia, eventually leading to acute respiratory distress syndrome (ARDS) promptly needing mechanical ventilation, a systematic recourse to intubation of every hypoxemic patient may be difficult to sustain in such peculiar context and may not be deemed appropriate for all patients. Then, it is essential that caregivers have a solid knowledge of physiological principles to properly interpret arterial oxygenation, to intubate at the satisfactory moment, to adequately manage mechanical ventilation, and, finally, to initiate ventilator weaning, as safely and as expeditiously as possible, in order to make it available for the next patient. Through the expected mechanisms of COVID-19-induced hypoxemia, as well as the notion of silent hypoxemia often evoked in COVID-19 lung injury and its potential parallelism with high altitude pulmonary edema, from the description of hemoglobin oxygen affinity in patients with severe COVID-19 to the interest of the prone positioning in order to treat severe ARDS patients, this review aims to help caregivers from any specialty to handle respiratory support following recent knowledge in the pathophysiology of respiratory SARS-CoV-2 infection.