MMP9 and acute respiratory distress syndrome: Both the ARDS and non-ARDS groups showed significantly higher plasma activity of MMP-2 and MMP-9 compared to HD (MMP-2: p < 0.0001 and p < 0.0001, respectively; MMP-9: p < 0.0001 and p < 0.0001, respectively) (Figure 1D and Figure 1E, respectively) (Table 2).