MMP9 and acute respiratory distress syndrome: Multiple regression analyses confirmed the observation that higher levels of active MMP-9, percent active MMP-9 and total MMP-8 at 48 hours of ARDS onset predicted the duration of mechanical ventilation (p<0.001, p = 0.005 and p = 0.004; respectively), after adjusting for disease etiology (pulmonary vs. non-pulmonary, infectious vs. non-infectious), disease severity (ex: PRISM scores, presence of MOSF), oxygenation defect (ex: P/F ratios, OI), age and gender.