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Respiratory failure

Background knowledge ๐Ÿง 


  • Condition where the lungs fail to meet the body’s oxygenation or carbon dioxide (CO2) elimination needs


  • Type 1 (Hypoxaemic): PaO2 < 8 kPa with normal or low PaCO2. Primary failure of oxygenation.
  • Type 2 (Hypercapnic): PaCO2 > 6.5 kPa. Failure of ventilation

Aetiology/Causes/Risk factors

  • Type 1: Pneumonia, pulmonary oedema, acute respiratory distress syndrome (ARDS), pulmonary embolism, asthma, interstitial lung disease
  • Type 2: COPD, neuromuscular disorders, chest wall deformities, obesity hypoventilation syndrome, drug overdose, central respiratory depression

Clinical Features ๐ŸŒก๏ธ


  • Dyspnoea
  • Confusion/drowsiness


  • Use of accessory respiratory muscles
  • Cyanosis
  • Altered consciousness or confusion (especially in hypercapnic)
  • Tachypnoea or bradypnoea

Investigations ๐Ÿงช

Initial tests

  • Arterial blood gas (ABG): determines type and severity of respiratory failure
  • Chest X-ray: to identify underlying causes (e.g., pneumonia, pneumothorax)
  • Spirometry: especially in chronic conditions like COPD
  • Blood tests: FBC to rule out anaemia; inflammatory markers, e.g. CRP; U&E

Learn more…

ABG interpretation is covered in full here.

Management ๐Ÿฅผ

Management of respiratory failure

  • Supplemental oxygen: to correct hypoxaemia
  • Non-invasive ventilation (NIV): especially beneficial in hypercapnic respiratory failure, for example in COPD exacerbations
  • Invasive mechanical ventilation: in cases where NIV is contraindicated or has failed

Learn more…

Oxygen therapy is covered here.
NIV is covered here.

Treat cause

  • Treat underlying cause (e.g. antibiotics for pneumonia, bronchodilators and steroids for asthma/COPD exacerbation)


  • Pneumonia
  • Acute respiratory distress syndrome (ARDS)
  • Barotrauma (with mechanical ventilation)
  • Death if respiratory failure not appropriately recognised/managed

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