Pulmonary Fibrosis During Severe COVID-19 Pneumonia

The COVID-19 pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS CoV-2), an emerging coronavirus, which has already infected 192 million people with a case fatality rate close to 2%. About 5% of patients infected with SARS CoV-2 have a critical form with organ failure. Among critical patients admitted to intensive care, about 70% of them will require ventilatory assistance by invasive mechanical ventilation (MV) with a mortality rate of 35% and a median MV duration of 12 days. The most severe lung damage resulting from SARS CoV-2 infection is the acute respiratory distress syndrome (ARDS). The virus infects alveolar epithelial cells and capillary endothelial cells leading to an activation of endothelium, hypercoagulability and thrombosis of pulmonary capillaries. This results in abnormal ventilation / perfusion ratios and profound hypoxemia. To date, the therapeutic management of severe SARS CoV-2 pneumonia lay on the early use of corticosteroids and Interleukin-6 (IL-6) receptor antagonist, which both reduce the need of MV and mortality. The risk factors of death in Intensive Care Unit (ICU) are: advanced age, severe obesity, coronary heart disease, active cancer, severe hypoxemia, and hepatic and renal failure on admission. Among MV patients, the death rate is doubled in those with both reduced thoracopulmonary compliance and elevated D-dimer levels. Patients with severe alveolar damage are at risk of progressing towards irreversible pulmonary fibrosis, the incidence of which still remain unknown. The diagnosis of pulmonary fibrosis is based on histology but there are some non-invasive alternative methods (serum or bronchoalveolar biomarkers, chest CT scan). We aim to assess the incidence of pulmonary fibrosis in patients with severe SARS CoV-2 related pneumonia. We will investigate the prognostic impact of fibrosis on mortality and the number of days alive free from MV at Day 90. Finally, we aim to identify risk factors of fibrosis.