Angiopoietins add a mechanistically informative dimension: angiopoietin-1 supports vascular stability via tyrosine kinase-2 (Tie2) signalling, whereas angiopoietin-2 promotes endothelial destabilisation and permeability; accordingly, circulating angiopoietin-2 (and a higher angiopoietin-2/angiopoietin-1 ratio) correlates with lung injury severity and mortality in ARDS cohorts, including surgical ICU populations [224,225]. This evidence concerns the gene ANGPT2 and acute respiratory distress syndrome.