Most common symptoms and signs are dyspnoea and hypoxaemia, which progress to acute respiratory failure.
Common causes are pneumonia, sepsis, aspiration, and severe trauma.
Mortality is between 40% and 50%.
Low tidal volume, plateau-pressure-limited mechanical ventilation is the primary treatment that has been shown to reduce mortality. In severe acute respiratory distress syndrome (ARDS), neuromuscular blockade and prone positioning may improve clinical outcomes.
Complications include pneumothorax, ventilator-associated pneumonia, multiple organ failure, and pulmonary fibrosis with prolonged respiratory failure.
This topic covers ARDS in patients over the age of 12 years.
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 three criteria:
Acute onset (within 1 week)
Bilateral opacities on chest x-ray
PaO₂/FiO₂ (arterial to inspired oxygen) ratio of ≤300 on positive end-expiratory pressure (PEEP) or continuous positive airway pressure (CPAP) ≥5 cm H₂O. 
If no risk factors for ARDS are present, then acute pulmonary oedema as a result of heart failure should be ruled out.
Professor of Medicine and Pathology, Microbiology and Immunology
Vanderbilt Medical Scholars Program
Division of Allergy, Pulmonary and Critical Care Medicine
Department of Medicine
Vanderbilt University School of Medicine
LW has served as a consultant for CSL Behring and Bayer. She has carried out contractual research for Boehringer Ingelheim and Global Blood Therapeutics. She has received grant funding from the US National Institutes of Health.
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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