FLT1 and acute respiratory distress syndrome: Because proteolytic cleavage of VEGF-R1 from lung epithelial cell surface has been reported during ARDS [35], we measured the level of soluble VEGF-1-receptor1 (sVEGF-R1) and found higher sVEGF-R1 levels in the COVID-19 patient group from day 1 to day 7 than in HCs (Fig. 2i).