The evolution of the ventilatory ratio is a prognostic factor in mechanically ventilated COVID-19 ARDS patients

Background: Mortality due to COVID-19 is high, especially in patients requiring mechanical ventilation. The purpose of the study is to investigate associations between mortality and variables measured during the first three days of mechanical ventilation in patients with COVID-19 intubated at ICU admission. Methods: Multicenter, observational, cohort study includes consecutive patients with COVID-19 admitted to 44 Spanish ICUs between February 25 and July 31, 2020, who required intubation at ICU admission and mechanical ventilation for more than three days. We collected demographic and clinical data prior to admission; information about clinical evolution at days 1 and 3 of mechanical ventilation; and outcomes. Results: Of the 2,095 patients with COVID-19 admitted to the ICU, 1,118 (53.3%) were intubated at day 1 and remained under mechanical ventilation at day three. From days 1 to 3, PaO2/FiO2 increased from 115.6 [80.0-171.2] to 180.0 [135.4-227.9] mmHg and the ventilatory ratio from 1.73 [1.33-2.25] to 1.96 [1.61-2.40]. In-hospital mortality was 38.7%. A higher increase between ICU admission and day 3 in the ventilatory ratio (OR 1.04 [CI 1.01-1.07], p = 0.030) and creatinine levels (OR 1.05 [CI 1.01-1.09], p = 0.005) and a lower increase in platelet counts (OR 0.96 [CI 0.93-1.00], p = 0.037) were independently associated with a higher risk of death. No association between mortality and the PaO2/FiO2 variation was observed (OR 0.99 [CI 0.95 to 1.02], p = 0.47). Conclusions: Higher ventilatory ratio and its increase at day 3 is associated with mortality in patients with COVID-19 receiving mechanical ventilation at ICU admission. No association was found in the PaO2/FiO2 variation

Clustering COVID-19 ARDS patients through the first days of ICU admission. An analysis of the CIBERESUCICOVID Cohort

Background Acute respiratory distress syndrome (ARDS) can be classified into sub-phenotypes according to different inflammatory/clinical status. Prognostic enrichment was achieved by grouping patients into hypoinflammatory or hyperinflammatory sub-phenotypes, even though the time of analysis may change the classification according to treatment response or disease evolution. We aimed to evaluate when patients can be clustered in more than 1 group, and how they may change the clustering of patients using data of baseline or day 3, and the prognosis of patients according to their evolution by changing or not the cluster.Methods Multicenter, observational prospective, and retrospective study of patients admitted due to ARDS related to COVID-19 infection in Spain. Patients were grouped according to a clustering mixed-type data algorithm (k-prototypes) using continuous and categorical readily available variables at baseline and day 3.Results Of 6205 patients, 3743 (60%) were included in the study. According to silhouette analysis, patients were grouped in two clusters. At baseline, 1402 (37%) patients were included in cluster 1 and 2341(63%) in cluster 2. On day 3, 1557(42%) patients were included in cluster 1 and 2086 (57%) in cluster 2. The patients included in cluster 2 were older and more frequently hypertensive and had a higher prevalence of shock, organ dysfunction, inflammatory biomarkers, and worst respiratory indexes at both time points. The 90-day mortality was higher in cluster 2 at both clustering processes (43.8% [n = 1025] versus 27.3% [n = 383] at baseline, and 49% [n = 1023] versus 20.6% [n = 321] on day 3). Four hundred and fifty-eight (33%) patients clustered in the first group were clustered in the second group on day 3. In contrast, 638 (27%) patients clustered in the second group were clustered in the first group on day 3.Conclusions During the first days, patients can be clustered into two groups and the process of clustering patients may change as they continue to evolve. This means that despite a vast majority of patients remaining in the same cluster, a minority reaching 33% of patients analyzed may be re-categorized into different clusters based on their progress. Such changes can significantly impact their prognosis

Preparation of top seeded YBa2Cu3O7 large single-domain tiles

Single domain superconductors with diameters up to 40 mm have been prepared by top seeding growth using Nd123 melt textured ceramics as seeds. We show that the use of these seeds is preferred over MgO single crystals to reduce the multinucleation problem. Large levitation forces and critical currents have been measured which demonstrate the single domain character of the samples.Postprint (author’s final draft

Fabrication of melt-textured cylinders and bars of (YBa2Cu3O7-Y2BaCuO5) superconductors

Cylinders and bars of bulk YBa2CuO7-Y2BaCuO5 textured ceramic composites (123-211) have been prepared through different directional solidification processes. Green ceramic preforms for the directional solidification process have been obtained by sintering the starting powders (123) and (211) in ceramic moulds at small pressures and by using a Cold Isostatic Pressing technique (CIP). The bars were melted and solidified in a vertical gradient furnace by the Bridgman technique at different rates up to 5mm/h. Cylinders were melted and solidified at 1-2ºC/h using single crystal seeds of different materials at different vertical gradients. We have studied the influence of (123)/(211) ratios, additions, particle size of the precursors and thermal treatments. The complex microstructure of these ceramic composites has been investigated by SEM, TEM and optical microscope. The directional solidification process allows to obtain quasi-single crystal superconductors with critical currents above 105A/cm2 at 77k and zero field.Postprint (published version

Preparation of top seeded YBa2Cu3O7 large single-domain tiles

Single domain superconductors with diameters up to 40 mm have been prepared by top seeding growth using Nd123 melt textured ceramics as seeds. We show that the use of these seeds is preferred over MgO single crystals to reduce the multinucleation problem. Large levitation forces and critical currents have been measured which demonstrate the single domain character of the samples

Fabrication of melt-textured cylinders and bars of (YBa2Cu3O7-Y2BaCuO5) superconductors

Cylinders and bars of bulk YBa2CuO7-Y2BaCuO5 textured ceramic composites (123-211) have been prepared through different directional solidification processes. Green ceramic preforms for the directional solidification process have been obtained by sintering the starting powders (123) and (211) in ceramic moulds at small pressures and by using a Cold Isostatic Pressing technique (CIP). The bars were melted and solidified in a vertical gradient furnace by the Bridgman technique at different rates up to 5mm/h. Cylinders were melted and solidified at 1-2ºC/h using single crystal seeds of different materials at different vertical gradients. We have studied the influence of (123)/(211) ratios, additions, particle size of the precursors and thermal treatments. The complex microstructure of these ceramic composites has been investigated by SEM, TEM and optical microscope. The directional solidification process allows to obtain quasi-single crystal superconductors with critical currents above 105A/cm2 at 77k and zero field