Acute Respiratory Distress Syndrome

ARDS is an acute, diffuse, inflammatory form of lung injury and life-threatening condition in seriously ill patients, characterized by poor oxygenation, pulmonary infiltrates, and acute onset. On a microscopic level, the disorder is associated with capillary endothelial injury and diffuse alveolar damage. ARDS is an acute disorder that starts within seven days of the inciting event and is characterized by bilateral lung infiltrates and severe progressive hypoxemia in the absence of any evidence of cardiogenic pulmonary edema. According to the Berlin definition, ARDS is defined by acute onset, bilateral lung infiltrates on chest radiography or CT scan of a non-cardiac origin, and a PaO/FiO ratio of less than 300 mm Hg. The Berlin definition differs from the previous American-European Consensus definition by excluding the term acute lung injury; it also removed the requirement for wedge pressure <18 mm Hg and included the requirement of positive end-expiratory pressure (PEEP) or continuous positive airway pressure (CPAP) of greater than or equal to 5 cm H0. Once ARDS develops, patients usually have varying degrees of pulmonary artery vasoconstriction and may subsequently develop pulmonary hypertension. ARDS carries a high mortality, and few effective therapeutic modalities exist to combat this condition.