Most common symptoms and signs are dyspnoea and hypoxaemia, which progress to acute respiratory failure.
Common causes are pneumonia, sepsis, aspiration, and severe trauma.
Diagnostic criteria are acute onset (<1 week), bilateral opacities on CXR, hypoxaemia with PaO2/inspired oxygen ratio ≤300 on PEEP or CPAP ≥5 cm H2O. In patients with no risk factor for ARDS, heart failure should be ruled out.
Mortality is between 30% and 50%.
Low tidal volume, plateau-pressure-limited mechanical ventilation is the only therapy that has been shown to reduce mortality.
Complications include pneumothorax, ventilator-associated pneumonia, multiple organ failure, and pulmonary fibrosis with prolonged respiratory failure.
Acute respiratory distress syndrome (ARDS) is a non-cardiogenic pulmonary oedema and diffuse lung inflammation syndrome that often complicates critical illness. The diagnosis of ARDS is based on fulfilling 3 criteria: acute onset (within 1 week), bilateral opacities on CXR, and a PaO2/FiO2 (inspired oxygen) ratio of ≤300 on PEEP or CPAP ≥5 cm H2O.  If no risk factor for ARDS is present, then heart failure as a cause of acute pulmonary oedema should be ruled out.
Associate Professor of Medicine
Vanderbilt Medical Scholars Program
Division of Allergy, Pulmonary and Critical Care Medicine
Department of Medicine
Vanderbilt University School of Medicine
LW declares that she has no competing interests.
Dr Lorraine Ware would like to gratefully acknowledge Dr Richard Fremont, a previous contributor to this monograph. RF declares that he has no competing interests.
Director of Medicine Critical Care Fellowship
Department of Anesthesia and Perioperative Care
University of California San Francisco
MAM declares that he has no competing interests.
Professor of Intensive Care Medicine
Royal Brompton Hospital
TE declares that he has no competing interests.
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