Acute respiratory failure

Last reviewed: 1 Sep 2023
Last updated: 30 Mar 2022



History and exam

Key diagnostic factors

  • direct trauma to the thorax and neck
  • dyspnea
  • confusion
  • tachypnea
  • accessory breathing muscle use
  • stridor
  • inability to speak
  • retraction of intercostal spaces
  • cyanosis
  • loss of airway/gag reflex
More key diagnostic factors

Other diagnostic factors

  • anxiety
  • headache
  • hypoventilation
  • cardiac rhythm disturbances
  • underlying neuromuscular disorder
  • drug use
  • seizure
  • coma
  • asterixis
  • papilledema
Other diagnostic factors

Risk factors

  • cigarette smoking
  • young age
  • older age
  • pulmonary infection
  • chronic lung disease
  • upper airway obstruction
  • lower airway obstruction
  • alveolar abnormalities
  • perfusion abnormalities
  • cardiac failure
  • peripheral nerve abnormalities
  • muscle system abnormalities
  • opioid and sedative medications
  • toxic fumes and gases
  • traumatic spinal injury
  • traumatic thoracic injury
  • central nervous system (CNS) disorders
  • acute vascular occlusion
  • pulmonary effusion
  • pneumothorax
  • hypercoagulable states
More risk factors

Diagnostic investigations

1st investigations to order

  • pulse oximetry
  • arterial blood gases
More 1st investigations to order

Investigations to consider

  • CBC
  • D-dimer
  • serum bicarbonate (HCO₃)
  • ECG
  • chest x-ray
  • pulmonary function tests
  • Urine or serum toxicology
  • chest CT
  • CT pulmonary angiography (CTPA)
  • ventilation/perfusion lung scan
  • capnometry
  • cardiothoracic ultrasound
More investigations to consider

Emerging tests

  • transcutaneous CO₂ monitoring

Treatment algorithm


airway obstruction

no acute upper airway obstruction: stable

no acute upper airway obstruction: unstable



Samuel J. Stratton, MD, MPH
Samuel J. Stratton


Fielding School of Public Health

David Geffen School of Medicine at UCLA

Los Angeles

Deputy Health Officer

Orange County Health Care Agency

Health Disaster Management/Emergency Medical Services

Santa Ana



SJS declares that he has no competing interests.

Peer reviewers

C. Michael Roberts, MA, MD, FRCP

Consultant Physician

Barts Health




CMR declares that he has no competing interests.

Ken Miller, MD, PhD

University of California

Irvine and Orange County Fire Authority




KM declares that he has no competing interests.

Christopher Kahn, MD, MPH

Assistant Professor of Clinical Emergency Medicine

Department of Emergency Medicine

University of California

Irvine and Orange County Fire Authority




CK declares that he has no competing interests.

  • Differentials

    • Hyperventilation secondary to metabolic acidosis
    • Hyperventilation secondary to anxiety
    • Sleep apnea
    More Differentials
  • Guidelines

    • Official ERS/ATS clinical practice guidelines: noninvasive ventilation for acute respiratory failure
    • Guideline for oxygen use in adults in healthcare and emergency settings
    More Guidelines
  • Patient leaflets

    Asthma in adults: what is it?

    Asthma in adults: what treatments work?

    More Patient leaflets
  • Videos

    Radial artery puncture animated demonstration

    Femoral artery puncture animated demonstration

    More videos
  • padlock-lockedLog in or subscribe to access all of BMJ Best Practice

Use of this content is subject to our disclaimer