Background COVID-19 is primarily a respiratory disease; however, there is also evidence that it causes endothelial damage in the microvasculature of several organs. The aim of the present study is to characterize in vivo the microvascular reactivity in peripheral skeletal muscle of severe COVID-19 patients. Methods This is a prospective observational study carried out in Spain, Mexico and Brazil. Healthy subjects and severe COVID-19 patients admitted to the intermediate respiratory (IRCU) and intensive care units (ICU) due to hypoxemia were studied. Local tissue/blood oxygen saturation (StO2) and local hemoglobin concentration (THC) were non-invasively measured on the forearm by near-infrared spectroscopy (NIRS). A vascular occlusion test (VOT), a three-minute induced ischemia, was performed in order to obtain dynamic StO2 parameters: deoxygenation rate (DeO2), reoxygenation rate (ReO2), and hyperemic response (HAUC). In COVID-19 patients, the severity of ARDS was evaluated by the ratio between peripheral arterial oxygen saturation (SpO2) and the fraction of inspired oxygen (FiO2) (SF ratio). Results Healthy controls (32) and COVID-19 patients (73) were studied. Baseline StO2 and THC did not differ between the two groups. Dynamic VOT-derived parameters were significantly impaired in COVID-19 patients showing lower metabolic rate (DeO2) and diminished endothelial reactivity. At enrollment, most COVID-19 patients were receiving invasive mechanical ventilation (MV) (53%) or high-flow nasal cannula support (32%). Patients on MV were also receiving sedative agents (100%) and vasopressors (29%). Baseline StO2 and DeO2 negatively correlated with SF ratio, while ReO2 showed a positive correlation with SF ratio. There were significant differences in baseline StO2 and ReO2 among the different ARDS groups according to SF ratio, but not among different respiratory support therapies. Conclusion Patients with severe COVID-19 show systemic microcirculatory alterations suggestive of endothelial dysfunction, and these alterations are associated with the severity of ARDS. Further evaluation is needed to determine whether these observations have prognostic implications. These results represent interim findings of the ongoing HEMOCOVID-19 trial. Trial registration ClinicalTrials.gov NCT04689477. Retrospectively registered 30 December 2020.

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With the growth in the number of PMUs in the electrical system, the discussion and understanding of performance requirements required in IEEE standard C37.118.1-2011 and its addendum IEEE C37.118.1a-2014 is of fundamental importance for the future specification, operation and maintenance of future interconnected power grids. This paper presents an analysis of two different algorithms for calculating synchrophasors in accordance with limits and test methods proposed in the IEEE standard. Results are presented using a hybrid simulation platform, in which the algorithms are implemented in a real PMU.

ResumoO teste de caminhada de seis minutos -TC6'-é amplamente utilizado para avaliação da capacidade física e do prognóstico de diversas doenças, em que a distância percorrida no TC6' (DTC6') é uma das principais variáveis para interpretá-lo. Vários estudos desenvolveram equações para obter a distância predita no TC6' -DPTC6', porém as equações de predição mais conhecidas na literatura foram desenvolvidas com indivíduos saudáveis. O objetivo deste estudo foi analisar e correlacionar a DTC6'com a DPTC6' por meio das equações de Enright et al.