Comparison of ultrasound signs, computed tomography data and morphological examination of the lungs in patients with coronavirus infection: post hoc analysis
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INTRODUCTION: Ultrasound examination (US) of the lungs has shown high efficiency in the diagnosis of COVID-19 pneumonia. The aim of the research was studying the correspondence of computed tomography (CT) US signs of the lungs and morphological data in patients with COVID-19 pneumonia. MATERIALS AND METHODS. The post hoc analysis included 388 patients who simultaneously underwent ultrasound and CT of the lungs. Lung ultrasound was performed according to the 16-zone "Russian Protocol". Morphological data were obtained from the results of pathoanatomic examination of deceased patients. RESULTS. The comparison of signs detected by CT and ultrasound of the lungs was performed during a multidimensional correspondence analysis. The analysis was carried out using a three-dimensional solution that explained 64.9% of inertia (p<0.001). CT signs of "ground glass opacity" (100%) corresponded to the B line at ultrasound (100%); CT of the consolidation sign (44.8%) – ultrasound signs of consolidation (46.9%); aerobronchogram of CT (34%) – aerobronchogram of ultrasound (36.9%); free liquid CT (11.1%) – free liquid Ultrasound (13.9%). CT signs of reticular changes (29.6%) and "cobblestone pavement" (12.4%) corresponded to various combinations of ultrasound signs of subpleural consolidation and B-lines. The B-lines were caused by the exudation of fluid and protein molecules into the intraalveolar space against the background of massive death of alveolocytes and formed by the development of intraalveolar edema and the formation of hyaline membranes. The ultrasonic sign of consolidation appeared in the airless zone of the lungs. Subpleural consolidation are caused by thickening and inflammatory infiltration of the pleura, diffuse alveolar damage, with intraalveolar edema, death and decay of alveolocytes, perivascular inflammatory cell reaction/ During treatment for more than 7 days, consolidation in the lung tissue developed due to the disorganization of the organ structure due to the progression of fibrosis. CONCLUSION. Multivariate correspondence analysis showed correlation of CT signs and US signs of the lungs. Morphological analysis showed polymorphism of histological data that caused the formation of ultrasound signs.
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Protocols, statistical analysis and the main results of the study of lung ultrasound in COVID-19 were published earlier. The clinical study was conducted at the Kirov Military Medical Academy of the Ministry of Defense of the Russian Federation, its conduct was approved by an independent Ethical Committee (Protocol No. 236 of 21.05.2020). 388 patients who underwent ultrasound and CT of the lungs were included in the post hoc analysis [25]. The analyzed study was prospective in nature. The criteria for inclusion in the study were: the age of patients 18-75 years; the development of community-acquired pneumonia; confirmed COVID-19 or suspected COVID-19. Criteria for non-inclusion: the presence of pneumothorax; chest injury or lung surgery in the anamnesis; background specific diseases (tuberculosis, sarcoidosis). Bedside ultrasound was performed using a portable ultrasound machine (Mindray M7, China) with a 2.5–5 MHz convexic sensor. The procedure for obtaining the image was standardized using the pre—adjustment of abdominal examination, the maximum depth is 18 cm, focusing on the pleural line. The amplification was adjusted to obtain the best image of the pleura, vertical artifacts and subpleural consolidations with or without air bronchograms. All harmonics and artifact reduction software have been disabled. The study was performed in a lying or sitting position, depending on the patient's condition. Lung ultrasound was performed according to the 16-zone "Russian Protocol" (eight zones on the right and left). CT was performed on a Philips Ingenuity machine (128 slices). The period between CT and ultrasound of the lungs is no more than 24 hours. Morphological data were obtained from the results of pathoanatomic examination of deceased patients. The material for histological analysis was collected in the areas of the most typical ultrasound signs. The areas of lung tissue fixed in buffered formalin solution were dehydrated and poured into paraffin blocks. Serial slices with a thickness of 5-6 microns were made on a rotary microtome NM 3600 ("MICROM Laborgerdte GmbH" - Germany), which were placed on slides. Histological sections were stained with hematoxylin and eosin, and then examined in a light field using an Olympus BX46 microscope. The data for this work were obtained from the original materials of the lung ultrasound study in COVID-19. With CT of the lungs, pathological signs were determined, which were recorded by lung segments. To verify the bronchopulmonary segments on CT, the numbering and anatomical nomenclature adopted by the London International Congress of Otolaryngologists in 1949 and the International Paris Congress of Anatomists in 1955 were used. Lung ultrasound used the projection of lung segments into the zones of the "Russian Protocol", in which pathological signs were determined and compared with CT data. The intra-segment spatial localization of the trait was taken into account.