Acute respiratory distress syndrome (ARDS)

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Last reviewed: 5 Aug 2025

Last updated: 31 May 2024

Acute respiratory distress syndrome (ARDS) typically presents with dyspnea and hypoxemia, 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, prone positioning, and extracorporeal membrane oxygenation (ECMO) 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.

Definition

Acute respiratory distress syndrome (ARDS) is a noncardiogenic pulmonary edema and diffuse lung inflammation syndrome that often complicates critical illness. The clinical definition of ARDS was updated in 2024 to include both intubated and nonintubated patients and to allow diagnosis of ARDS in resource-limited settings.[1] Diagnosis of ARDS is based on fulfilling three criteria:

Acute onset (within 1 week)
Bilateral opacities on chest radiography or computed tomography (CT), or bilateral B lines and/or consolidations on ultrasound not fully explained by effusions, atelectasis, or nodules/masses
PaO₂/FiO₂ (arterial to inspired oxygen) ratio of ≤300 or SpO2/FiO2 (pulse oximetric saturation to inspired oxygen) ratio of ≤315.[1]

If no risk factors for ARDS are present, then acute pulmonary edema as a result of heart failure should be ruled out.

History and exam

Key diagnostic factors

low oxygen saturation
acute respiratory failure

Full details

Other diagnostic factors

critically ill patient
dyspnea
increased respiratory rate
pulmonary crepitations
low lung compliance
fever, cough, pleuritic chest pain
frothy sputum

Full details

Risk factors

sepsis
aspiration
pneumonia
severe trauma
blood transfusions
lung transplantation
pancreatitis
history of alcohol misuse
burns and smoke inhalation
drowning
e-cigarette and vaping product use
Immunotherapy
drug overdose
cigarette smoking

Full details

Diagnostic tests

1st tests to order

chest x-ray
arterial blood gases
sputum culture
blood culture
urine culture
amylase and lipase

Full details

Tests to consider

brain natriuretic peptide (BNP)
echocardiogram
pulmonary artery catheterization
bronchoalveolar lavage or endotracheal aspirate
CT scan of the thorax
Lung ultrasound
viral testing
open lung biopsy

Full details

Treatment algorithm

ACUTE

all patients

Contributors

Authors

Lorraine B. Ware, MD

Ralph and Lulu Owen Professor of Medicine

Professor of Pathology, Microbiology and Immunology

Director

Vanderbilt Medical Scholars Program

Division of Allergy, Pulmonary and Critical Care Medicine

Department of Medicine

Vanderbilt University School of Medicine

Nashville

Disclosures

LBW has received consulting fees from Arrowhead, Akebia, Santhera, and Global Blood Therapeutics, all unrelated to the topic of this article. LBW has received research funding (to her institution) from the US National Institutes of Health, Boerhinger Ingelheim, and Genetech Inc., unrelated to the topic of this article. LBW holds stock in Virtuoso Surgical, unrelated to the topic of this article.

Acknowledgements

Dr Lorraine Ware would like to gratefully acknowledge Dr Richard Fremont, a previous contributor to this topic.

Disclosures

RF declares that he has no competing interests.

Peer reviewers

Michael A. Matthay, MD

Director of Medicine Critical Care Fellowship

Department of Anesthesia and Perioperative Care

University of California San Francisco

Disclosures

MAM declares that he has no competing interests.

Timothy Evans, MBBS

Professor of Intensive Care Medicine

Royal Brompton Hospital

London

Disclosures

TE declares that he has no competing interests.

Peer reviewer acknowledgements

BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.

Disclosures

Peer reviewer affiliations and disclosures pertain to the time of the review.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Matthay MA, Arabi Y, Arroliga AC, et al. A new global definition of acute respiratory distress syndrome. Am J Respir Crit Care Med. 2024 Jan 1;209(1):37-47.Full text Abstract

Bos LDJ, Ware LB. Acute respiratory distress syndrome: causes, pathophysiology, and phenotypes. Lancet. 2022 Oct 1;400(10358):1145-56.Full text Abstract

Janz DR, Ware LB. Approach to the patient with the acute respiratory distress syndrome. Clin Chest Med. 2014 Dec;35(4):685-96.Full text Abstract

Qadir N, Sahetya S, Munshi L, et al. An update on management of adult patients with acute respiratory distress syndrome: an official American Thoracic Society clinical practice guideline. Am J Respir Crit Care Med. 2024 Jan 1;209(1):24-36.Full text Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials
- Coronavirus disease 2019 (COVID-19)
- Acute heart failure
- Bilateral pneumonia
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Guidelines
- Mechanical ventilation in adult patients with acute respiratory distress syndrome
- Symptom assessment for mechanically ventilated patients: principles and priorities
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Acute respiratory distress syndrome
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Acute respiratory distress syndrome (ARDS)

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic tests

1st tests to order

Tests to consider

Treatment algorithm

all patients

Contributors

Authors

Lorraine B. Ware, MD

Disclosures

Acknowledgements

Disclosures

Peer reviewers

Michael A. Matthay, MD

Disclosures

Timothy Evans, MBBS

Disclosures

Peer reviewer acknowledgements

Disclosures

References

Key articles

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials

Guidelines

Patient information

Videos

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice