CO2 narcosis


  • Increased CO2 in the blood leading to depressed mental status
  • Most commonly seen in acute exacerbations of obstructive pulmonary diseases (e.g. COPD, asthma)
  • Can also be seen in SCUBA divers

Clinical Features

Differential Diagnosis

Altered mental status

Diffuse brain dysfunction

Primary CNS disease or trauma



  • VBG (ABG not required to make this diagnosis[1])


  • Hyperventilation with either NIPPV or intubation/mechanical ventilation depending on severity and patient's mental status


  • Admission to a monitored setting

See Also


  1. McCanny P, Bennett K, Staunton P, McMahon G. Venous vs arterial blood gases in the assessment of patients presenting with an exacerbation of chronic obstructive pulmonary disease. Am J Emerg Med. 2012; 30(6):896-900.
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