Acute Respiratory Distress Syndrome (ARDS) is a syndrome of inflammation and increased permeability associated with a constellation of clinical, radiologic, and physiologic abnormalities unexplained by elevations in left atrial or pulmonary capillary pressure.

All definitions of this syndrome include patients who meet the following criteria:

• Identifiable associated condition

• Acute onset

• Pulmonary artery wedge pressure </=18 mm Hg or absence of clinical evidence of left atrial hypertension

• Bilateral infiltrates on chest radiography

• Acute lung injury (ALI) is present if Pao₂/Fio₂ ratio is </= 300

• Acute respiratory distress syndrome is present if Pao₂/Fio₂ ratio </= 200

ARDS = acute respiratory distress syndrome; Pao₂ = partial pressure of arterial oxygen; Fio₂ = percentage of inspired oxygen.

Clinical Conditions Associated with Development of Acute Respiratory Distress Syndrome

Direct lung injury

• Pneumonia

• Aspiration of gastric contents

• Inhalation injury

• Near drowning

• Pulmonary contusion

• Fat embolism

• Reperfusion pulmonary edema post lung transplantation or pulmonary embolectomy

Indirect lung injury

• Sepsis

• Severe trauma

• Acute pancreatitis

• Cardiopulmonary bypass

• Massive transfusions

• Drug overdose