MPO and Chronic colitis: HBOT studied in acute (2 days) and chronic (14 days) colitis; compared to sham treatment, HBOT significantly ameliorated macroscopic, but not microscopic, damage in chronic colitis but not acute colitis; HBOT also significantly reduced myeloperoxidase activity (an index of the accumulation of neutrophils) in acute colitis and decreased plasma carbonyl content (a marker of oxidative damage) in chronic colitis