Федеральный дистанционный консультативный центр анестезиологии и реаниматологии на базе Первого МГМУ им. И.М. Сеченова

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The paper presents an experimental study of a convective flow in a rectangular cell of length L, width W and depth H, filled with water, heated from the bottom and cooled from the top, with a heat-insulating disk floating at a fixed height h (the disk diameter is slightly smaller than the cavity width). Such a system exhibits a range of modes, including periodic movements of the float along the cavity, chaotic motions of various types, and drift of the disk to the edge of the cavity without further movements. In addition to the Rayleigh, Prandtl numbers and the cavity dimension ratio (L/H), usual for convective systems, the structure of convective flows in the cavity depends on geometric parameters associated with the floating disk: the relative height of the body position (h/H) and the body size to the cavity length ratio (D/L). Experiments were performed for fixed W=100mm, H=40mm, D=98mm, and h=4mm, but different lengths 170mm < L < 500mm. It is shown that periodic motions occur only in a limited range of the body size to the cavity size ratio. As the length of the cavity increases, a chaotic mode of intermittent motion of the disc occurs; at the maximum cavity length considered, the disk is shifted to the extreme position and remains there. The structure of the convective flow at different phases of periodic motions has been reconstructed by PIV (particle image velocimetry) technique.

Aim. In a retrospective study, we evaluated factors associated with the early development of septic shock in patients with severe COVID-19. Materials and methods. We collected medical records of the intensive care unit patients submitted by the local COVID-19 hospitals across Russia to the Federal Center for the Critical Care at the Sechenov First Moscow State Medical University (Sechenov University). Septic shock in crticially ill patients requiring mechanical ventilation was defined as a need in vasopressors to maintain blood pressure. Results. We studied 1078 patients with severe COVID-19 who were admitted to the intensive care units for respiratory support. There were 611 males and 467 females. The mean age was 61.013.7 years. Five hundred twenty five medical records (48.7%) were received from the Moscow hospitals, 159 (14.7%) from the Moscow region, and 394 (36.5%) from the hospitals located in 58 regions of the Russian Federation. In 613 (56.9%) patients, diagnosis of SARS-CoV-2 infection was confirmed by PCR, and in the other cases it was established on the basis of the clinical picture and the results of the chest CT scan. Septic shock developed in 214 (19.9%) of 1078 patients. In the logistic regression model, the risk of septic shock in patients older than 50 years was higher than in patients of a younger age (OR 2.34; 95% CI 1.533.67; p0.0001). In patients with more severe SARS-CoV-2 infection, there was an increase in the prevalence of cardiovascular diseases, including coronary heart disease and atrial fibrillation, type 2 diabetes and malignant tumors. The risk of septic shock in patients with three or more concomitant diseases was higher than in patients without any concomitant chronic diseases (OR 1.76; 95% CI 1.762.70). Conclusion. The risk of septic shock in patients with acute respiratory distress syndrome induced by SARS-CoV-2 is higher in patients older than 50 years with concomitant diseases, although a severe course of the disease is also possible in younger patients without any concomitant disorders.

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