PECAM1 and acute respiratory distress syndrome: Thus, under normal conditions, the presence of low levels of sPECAM1 is indicative of normal functioning of PECAM1 as counteracting the tendency of leukocytes to leave the vasculature, whereas higher circulating levels of sPECAM1, as occurs during inflammatory conditions such as sepsis, ARDS and VILI, could serve as diagnostic and prognostic biomarkers of endothelial dysfunction.