Pathogenesis of pulmonary complications COVID-19

Abstract

Basically, COVID-19 is a coronavirus SARS-CoV-2 infection. COVID-19-associated pneumonia is a heterogeneous dis-ease (tracheobronchitis, diffuse alveolar injury and vas-cular injury) that leads to unusual clinico-pathological manifestations such as early-onset chest pain, pulmonary infarction, pulmonary and systemic thromboembolism, pathogenetically linked to extensive capillary, arteriolar and venular thrombosis. Platelet and/or fibrin capillary microthrombi were present in most cases. Early ground glass opacities, detected by computed tomography, re-sembling lung infarctions associated with pulmonary embolism, indicate new vascular pathology in COVID-19. Although most COVID-19 patients recover, a significant number of patients develop serious complications. Bilateral pneumonia, with prevailing acute respiratory distress syndrome, is a sign of severe COVID-19 disease, but the involvement of other organ systems, namely the cardiovascular system, kidneys, liver and central nervous system, occurs in at least half of fatal COVID-19 cases. Besides respiratory failure requiring mechanical ventilation, patients with severe COVID-19 often have intravascular coagulopathy, manifestations of systemic inflammation, and diffuse microvascular lesions found postmortem. In this review, the authors analyze the pathophysiological mechanisms that may explain how the virus when entering the body can cause COVID-19-associated pneumonia, systemic inflammation, thrombosis, and vascular dysfunction. The authors also review the role of the renin-angiotensin-aldosterone system in the context of COVID-19. All these observations highlight the high complexity of COVID-19 disease, involving several compartments, from upper airways (trachea, bronchi) to lung parenchyma, and the vascular bed. A tricompartmental model of pulmonary and systemic pathology in severe COVID-19 is proposed, which covers the known pathological and clinical features of severe COVID-19. A deeper understanding and better knowledge of the pathogenetic changes in COVID-19 will lead to more appropriate diagnostic and therapeutic approaches for clinical management.