Current concepts regarding adult respiratory distress syndrome.

Adult respiratory distress syndrome (ARDS) is a multietiologic acute and progressive pulmonary dysfunction that may be precipitated by any of a number of pathogenic agents. Clinical and experimental studies suggest that activation of complement and blood neutrophils plays a significant role in the development of pulmonary vascular injury, which is an important pathophysiological feature of ARDS. Although the specific cellular and biochemical mechanisms resulting in the development of ARDS are unknown, it has been suggested that oxygen-derived free radicals generated from complement-activated granulocytes may be involved, directly or indirectly, in the destruction of lung vascular endothelium and alveolar tissue matrix. This hypothesis is supported by recent experimental studies showing that acute lung injury secondary to systemic complement activation can largely be prevented by interventions that scavenge for hydroxyl radicals or restrict availability of ionic iron.