Keywords: 6MWT, 6 minutes walking test; ARDS, acute respiratory distress syndrome; COVID-19, coronavirus disease 2019; CT, computed tomography; DLCO, diffusing capacity for carbon monoxide; FEV1, forced expiratory volume during the first second of the forced breath; FVC, forced vital capacity; GGO, ground-glass opacities; ICU, intensive care unit; IMV, invasive mechanical ventilation; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; TLC, total lung capacity; TSS, total severity score.