Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a clinical syndrome of severe dyspnea of rapid onset, hypoxemia, and diffuse pulmonary infiltrates leading to respiratory failure. ARDS is caused by diffuse lung injury from many underlying medical and surgical disorders. The lung injury may be direct, as occurs in toxic inhalation, or indirect, as occurs in sepsis ( Table 268-1 ) . The clinical features of ARDS are listed in Table 268-2 . Acute lung injury (ALI) is a less severe disorder but has the potential to evolve into ARDS ( Table 268-2 ). The arterial (a) PO 2 (in mmHg)/FIO 2 (inspiratory O 2 fraction) <200 mmHg is characteristic of ARDS, while a PaO 2 /FIO 2 between 200 and 300 identifies patients with ALI who are likely to benefit from aggressive therapy. The annual incidences of ALI and ARDS are estimated to be up to 80/100,000 and 60/100,000, respectively. Approximately 10% of all intensive care unit (ICU) admissions suffer from acute respiratory failure, with ∼20% of these patients meeting criteria for ALI or ARDS.