ABSTRACT
Background: Pulmonary fibrosis persists long after recovering from coronavirus disease 2019 (COVID-19) infection, thereby reducing quality of life and lung function. We aimed to evaluate the prevalence and risk factors for pulmonary fibrosis in patients with severe COVID-19 pneumonia requiring mechanical ventilation, a high-risk group for developing pulmonary fibrosis. Methods: Clinical data and chest computed tomography (CT) scans of patients with severe COVID-19 pneumonia requiring mechanical ventilation were retrospectively collected from nine hospitals in South Korea. Fibrotic-like changes on chest CT were visually assessed. Results: We included 125 patients with a mean age of 68.5 years, 60.8% men and 7.2% having underlying lung disease. Based on follow-up chest CT (the median interval: 38.0 days, interquartile range: 24.0–68.0 days), 94 (75.2%) patients exhibited fibrotic-like changes, with traction bronchiectasis and/or bronchiolectasis being the most common change (60.8%). Adjusted Cox regression analysis revealed as association between hemoglobin levels ≤9 g/dL and an increased risk of pulmonary fibrosis development (HR: 3.182, 95% Cl: 1.203–8.415, P=0.025). Among all patients, 17.6% died during hospitalization and 71.2% experienced complications, including intubation-related airway injury (12.8%), ventilator-associated pneumonia (44.8%), lung injury (11.2%), and hemodynamic disturbance (33.4%). In-hospital mortality (16.1% vs. 18.1%) and complications (67.7% vs. 72.3%) were similar between patients with and without fibrotic-like changes. Conclusion: Our study demonstrated that in patients with severe COVID-19 pneumonia requiring mechanical ventilation, chest CT revealed fibrotic-like changes in approximately three-fourths of patients. Low hemoglobin levels might be associated with pulmonary fibrosis in severe COVID-19 pneumonia.