TGFB1 and COVID-19: Consequently, 6-months after ICU-discharge from severe ARDS caused by COVID-19, we analyzed, as primary endpoint, the expression of active TGF-β1 and, as secondary endpoints, other fibrosis-related molecules in plasma and exhaled breath condensate (EBC) in relation to the presence or absence of alveolar-capillary membrane thickening, estimated through the DmCO/VA ratio.