In the current study, subjects who went on to require longer ARDS-related ventilator support and had fewer ventilator-free days demonstrated higher active MMP-9, fraction of active MMP-9 and total MMP-8 levels at 48 hours of ARDS, independent of age, gender, oxygenation defect, disease etiology and severity of illness. The gene discussed is MMP9; the disease is acute respiratory distress syndrome.