Last reviewed: 18 Apr 2021
Last updated: 09 Apr 2020



History and exam

Key diagnostic factors

  • low oxygen saturation
  • acute respiratory failure

Other diagnostic factors

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

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
  • drug overdose
  • cigarette smoking

Diagnostic investigations

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)
  • echocardiogram
  • pulmonary artery catheterization
  • bronchoalveolar lavage or endotracheal aspirate
  • CT scan of the thorax

Treatment algorithm


Lorraine Ware

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 advisory board fees from Bayer, Quark, and CSL Behring and contractual research support to her institution from Global Blood Therapeutics, Boehringer Ingelheim, and CSL Behring.

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.

Peer reviewersVIEW ALL

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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