PI3 and acute respiratory distress syndrome: At the onset of ARDS, the ARDS patients had significantly higher HNE but lower PI3 resulting in increased HNE/PI3 ratio (mean = 14.5; 95% CI, 10.9–19.4), compared with patients who did not develop ARDS during the ICU hospitalization which had a higher but not statistically significant HNE/PI3 ratio (mean = 6.5; 95% CI, 4.9–8.8) than that of healthy individuals (reference samples: mean = 3.9; 95% CI, 2.7–5.9).