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. This evidence concerns the gene MMP8 and acute respiratory distress syndrome.