Acute respiratory distress syndrome (ARDS) typically presents with dyspnoea and hypoxaemia, which progress to acute respiratory failure.
Common causes are pneumonia, sepsis, aspiration, and severe trauma.
Mortality is between 30% and 50%.
Low tidal volume, plateau-pressure-limited mechanical ventilation is the primary treatment that has been shown to reduce mortality. In severe 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 or continuous positive airway pressure ≥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.
History and exam
Key diagnostic factors
- presence of risk factors
- low oxygen saturation
- acute respiratory failure
Other diagnostic factors
- critically ill patient
- increased respiratory rate
- pulmonary crepitations
- low lung compliance
- fever, cough, pleuritic chest pain
- frothy sputum
- severe trauma
- blood transfusions
- lung transplantation
- history of alcohol misuse
- burns and smoke inhalation
- e-cigarette and vaping product use
- drug overdose
- cigarette smoking
1st investigations to order
- chest x-ray
- arterial blood gases
- sputum culture
- blood culture
- urine culture
- amylase and lipase
Investigations to consider
- brain natriuretic peptide (BNP)
- pulmonary artery catheterisation
- bronchoalveolar lavage or endotracheal aspirate
- CT scan of the thorax
- viral testing
- open lung biopsy
Lorraine Ware, MD
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 received research contract support from CSL Behring, Boehringer Ingelheim and Genentech. She has received consulting fees and/or scientific advisory board fees from CSL Behring, Merck, Foresee, Citius, and Boehringer Ingelheim.
Dr Lorraine Ware would like to gratefully acknowledge Dr Richard Fremont, a previous contributor to this topic.
RF declares that he has no competing interests.
Michael A. Matthay, MD
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.
Timothy Evans, MBBS
Professor of Intensive Care Medicine
Royal Brompton Hospital
TE declares that he has no competing interests.
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