Background Venous thromboembolism (VTE) with the prevalence of pulmonary microcirculatory thrombosis is considered a common complication of novel coronavirus disease (COVID-19) that develops despite anticoagulation. Methods The clinical course of the disease and the autopsy findings of seven deceased patients with verified COVID-19 were analyzed. The chest computed tomography (CT) scan was routinely performed while CT pulmonary angiography and a duplex ultrasound scan (DUS) of the lower limbs were used in cases of suspected VTE. The VTE prophylaxis was administered to all patients with intermediate or therapeutic doses of low-molecular-weight heparin. The histological examination of the lung tissue and other organs was performed with particular attention paid to the pulmonary vasculature. Results Venous thromboembolism, including deep vein thrombosis in one patient and pulmonary artery thrombosis in two patients, was confirmed by imaging tests despite anticoagulation. Systemic thrombolysis was performed in two patients with putative and confirmed pulmonary embolism. An autopsy revealed the signs of acute respiratory distress syndrome in all seven patients. Abnormalities of lung vessels were found in all cases and were represented by dystrophy and necrosis in the endothelium and muscle fibers, and by infiltration by plasmatic cells, neutrophils, and lymphocytes. Multiple clots of variable maturity were observed. All those changes developed despite anticoagulation and were preserved after systemic thrombolysis. Conclusion Inflammatory and prothrombotic changes in the arterial wall in parallel with the lack of lung perfusion may cause diffuse arterial thrombosis in the lungs. This background may be responsible for the low response to systemic anticoagulation and thrombolysis in severe forms of COVID-19.

Pulmonary artery thrombosis is one of the crucial mechanisms of severe COVID-19 development. Histological examination reveals widespread microvascular thrombosis in 87 % and large branches pulmonary artery thrombosis in 13 % of deceased patients. Caused by viral and immune cytotoxic effect thrombotic lung vasculopathy appears to be the main trigger of pulmonary artery thrombosis. In this study we examined 7 lungs obtained from patients who died from COVID-19. Thrombotic lung vasculopathy was typical sign of all 7 lungs. Endothelial cell destruction, media fibrinoid necrosis, neutrophil and lymphocytic infiltrates of the arterial wall and perivascular tissues were the basic histological changes in the lung arteries of different diameters. All this fatal changes developed independently of the therapeutic and prophylactic anticoagulation.

Aim. We aimed to study the histological and thrombotic changes in lung vessels in patients who died with COVID-19, to access the correlation between anticoagulation therapy (ACT) and thrombotic events (TE), treatment results, clinical and laboratory patients' characteristics.Material and Methods. We retrospectively analyzed treatment results of patients hospitalized with COVID-19 and lung vessel samples of the deceased patients. Dynamic changes and highest levels of D-dimer and fibrinogen were studied in its correlation with the disease severity according to SOFA score, computer tomographic (CT) results, lung, renal and hepatic dysfunction. The association between different doses of ACT and treatment results, laboratory indicators and thrombotic events was accessed. The histological lung vessels examination was performed using Martius Scarlet Blue (MSB)staining.Results. 313 patients were included in the study (61 patients died). The median age of hospitalized patients was 60 years (IQR 51-66 years). The frequency of the intravitallyconfirmed TE was 4,8%. The strong statistical association was revealed between D-dimer level and 3-4 points SOFA score, patients' mortality, oxygen support requirement, CT3-CT4 pneumonia, glomerular filtration rate and TE. There was no mortality in patients with D-dimer normal references, but in cases with three times elevation reached 13%, 48,5% - in cases with 3-6 times elevation and 64,6% - in cases with more than 6 times elevation. The strong statistical association was registered between fibrinogen and SOFA score, CT 3-4 pneumonia, patients' mortality. D-dimer and fibrinogen levels demonstrated weak correlation. There was no statistical correlation between prophylactic, intermediate and therapeutic ACT and D-dimer and fibrinogen levels, CT results, patients' mortality. MSBstaining was used in 36 deceased patients tissue samples. 1394 lung vessels were analyzed. Lung vessels thrombi persisted in samples of all 36 patients (100%). Vessels with the diameter 3,5-30 mm were thrombosed in 7%, with the diameter 0,034-0,84 mm - in 48%, with the diameter 0,85-3,4 mm - in 45%. The frequency of thrombi persisted 06 hours, 6-12 hours, 12-18hours, 18-24 hours and more than 24 hours was12%, 14%, 62%, 5% and 7% respectively.Conclusion. Thrombi of different ages from fresh to organized were observed in one third of lung vessels in all deceased patients. Lung vessels thrombosis plays an important role in pathogenesis and thanatogenesis of COVID-19. The D-dimer level correlates with lung, renal dysfunction, patients' mortality and doesn't show any correlation with ACT and can be accepted as a criterion of lung vessel thrombotic progression.

A clinical experience of using non-invasive nasal ventilation in patients after coronavirus disease 2019 (COVID-19) complicated by bilateral multisegmental pneumonia. It has been shown that, against the background of medication therapy, there is a restoration of ventilation-perfusion relationships in lung atelectasis areas, which is confirmed by spirometry and chest computed tomography. Implementation of non-invasive nasal ventilation against the background of drug therapy to restructure diffuse pulmonary fibrosis allows to accelerate the onset of dynamic exercise due to improved exercise tolerance.

BACKGROUND: The development of ways of rehabilitation of patients after polysegmental viral pneumonia that enable the collapsed alveoli being transferred to a ventilated and actively perfused state is certainly relevant. In this regard, non-invasive respiratory support can be considered as a reasonable additional method of treatment for these patients. MATERIALS AND METHODS: The study included 40 patients after bilateral polysegmental pneumonia caused by the SARS CoV-2 virus. The first group of patients (21 people), in addition to the standard treatment, underwent non-invasive assisted intranasal ventilation in the BiPAP mode with a final expiratory pressure of 4-8 cm of water. Art. 60 minutes three times a day for 10-12 days. The second group (19 people) did not receive ventilation benefits. Before the start of therapy and at the end of the course, spirometry, computed tomography (CT) of the chest organs were performed with the calculation of the volume of the affected lung tissue according to the Thoracic VCAR program. RESULTS: upon completion of the course of treatment and rehabilitation measures in patients of the first group, the following was observed: a decrease in atelectatic changes and pneumofibrosis, an increase in the volume of ventilated areas of the lungs, the volume of the affected lung tissue according to CT significantly decreased (on average, up to 26 9.8%; p0.05). There was a significant improvement in the indicators of spirometry in the first group. The increase in FEV1 was 25-32%, while VC was 27-31%. When evaluating long-term pulse oximetry, the average saturation at night in these patients increased from 91.22.1 to 96.41.8 (p0.05). Clinical improvement in patients of the first group led to a decrease in bed-days to an average of 15.4, while in patients of the second group it averaged 23.4 days. CONCLUSION: The use of assisted intranasal ventilation returns the ventilation-perfusion ratio in atelectated areas of the lungs, which is confirmed by a significant improvement in clinical and instrumental parameters.