A simple linear correlation analysis showed a strong correlation between BALF histone levels and BALF LDH (r = 0.6161, p = 0.002) and between histones and BALF MPO (r = 0.5783, p = 0.004) (Table 2), which suggested that the elevated extracellular histones were possibly derived from damaged lung tissue cells as well as inflammatory cell infiltration during ARDS. This evidence concerns the gene MPO and acute respiratory distress syndrome.