MMP9 and acute respiratory distress syndrome: In the rat model of mild-to-moderate ARDS used herein, we found that, at low mechanical power, higher VT resulted in increased PaCO2, DAD scores, and gene expression of mediators associated with inflammation (IL-6), alveolar stretch (amphiregulin), damage to epithelial cells (CC16), and extracellular matrix (MMP-9 and syndecan-1).