The influence of obesity (with and without passive smoking) on the formation of pathomorphological changes in the lungs was studied in 4 groups of sexually mature male rats: the control group (CL), the group with isolated alimentary obesity (O), the group exposed to isolated exposure to tobacco smoke (S), the group with combined dietary obesity and exposure to tobacco smoke (OS) after 4 months of the experiment. The morphological changes found in the CL group were insignificant. In group S, the presence of changes characteristic of chronic bronchitis and focal emphysema was established. Pathomorphological changes typical for the chronic obstructive pulmonary disease were found in group O: chronic bronchitis, initial manifestations of bronchiectasis formation, pulmonary emphysema, focal pneumosclerosis, and initial manifestations of pulmonary hypertension. In the OS group, the changes were not qualitatively different from those in the O group. It was found that the changes characteristic of chronic obstructive pulmonary disease developed in rats with simulated obesity, regardless of whether the smoking model was used. Key words: experimental obesity, smoking, rats, pathomorphological changes in the lungs

Introduction. Worldwide, more than 182 million cases of COVID-19 and more than 3.9 million deaths have been confi rmed since the virus was fi rst identifi ed. Advanced age and some comorbid conditions, such as diabetes and cardiovascular diseases, are considered risk factors for the adverse course of the discussed pathology. In recent years, several reports have been published about the results of the pathological examination of patients with COVID-19. Most often, in fatal cases, diff use alveolar damage is described, which is characterized by intraalveolar edema, the appearance of “hyaline” membranes and the proliferation of pneumocytes and fi broblasts. However, the nature of the damage caused by SARS-CoV-2 remains unclear. The study of pathomorphological changes in severe fatal cases of COVID-19 is important for a better understanding of pathogenetic mechanisms of the development of pulmonary complications and the development of new eff ective methods of antiviral treatment. The aim of the current study is to evaluate the gross and microscopic fi ndings in COVID-19 patients’ autopsy to investigate the clinicopathologic basis for adverse outcomes with a fatal course of the disease. Methods. A retrospective analysis of 1036 consecutive autopsies associated with COVID-19 in 2020 was conducted based on Lviv Regional Offi ce for Autopsy and Lviv Railway Clinical Hospital. The diagnosis of COVID-19 was confi rmed by clinical signs of viral pneumonia, nasopharyngeal smear analysis, and radiological changes. A statistical study was performed with IBM SPSS Statistics 24.0. Results. The majority (72.4%) were elderly (60+) males (54.1±1.5%) and females (45.9±1.5%), with an age range from 19 to 93 years (mean age 66.9 ± 0.4 years). All examined patients had pneumonia, which was detected during a clinical examination with CT diagnosis and confi rmed at autopsy. The acute exudative phase of pneumonia was diagnosed in 18.5±1.2% of cases, proliferative phase – in 18.5±1.2%, and fi brotic phase – in 5.9±0.7%. And in 53.5±1.5% of cases, signs of progressive fi brosis associated with exudative lesions prevailed. COVID-19 was the single original cause of death in 88.7±1.0% of cases. The following were identifi ed in the lungs: typical virus-induced changes in epithelial cells of the trachea, bronchi, bronchioles and alveoli (100%, n=1036); diff erent phases of diff use alveolar damage in the majority of cases (96.5±0.6%); manifestations of innate immunity were described; pathological changes in the microvasculature (large vessel thrombi were detected in 37.9±1.5%). Conclusion. Our study results prove the importance of pathological examination of tissues during autopsies to determine the pathophysiological mechanisms and underlying causes of death of patients with COVID-19. Keywords: COVID-19, SARS-CoV-2, diff use alveolar damage, vessel thrombi, elderly males.