ANGPT2 and acute respiratory distress syndrome: Pathological pieces of evidence confirmed that patients with direct ARDS had localized damage to the lung epithelium, whereas patients with indirect ARDS had a systemic endothelial injury caused by diffuse vascular inflammation, where surfactant protein D and angiopoietin-2 were identified as specific plasma biomarkers of direct and indirect ARDS, respectively, both of which were prognostic of mortality [95].