Hypercapnia


  • The blood contains carbon dioxide, a "waste product" of cellular metabolism that is exhaled by the lungs at the same time that oxygen is taken in.  The normal concentration (partial pressure) of carbon dioxide in the blood is 40 mm Hg.  Hypercapnia is when the carbon dioxide level goes above 45 mm Hg. (though it usually needs to be higher than this for symptoms to occur).
  • Hypercapnia commonly occurs in severe Emphysema.  Oxygen given to patients with Emphysema may reduce their ability to breathe, resulting in Hypercapnia.  This is why exact doses of oxygen are usually figured out for those with Emphysema so that they receive neither too little nor too much oxygen. Note: if a patient is actively short of breath, never withhold oxygen from him.

  • Shortness of breath
  • Headache
  • Delirium
  • Obtundation (dulled alertness)


  • Examination
    1. Heart racing
    2. Rapid breathing due to Emphysema
    3. Shallow or decreased breathing due to neuromuscular disorders or medications
    4. Elevated blood pressure
    5. Impaired consciousness
    6. Fundoscopic exam may show papilledema
    7. Asterixis (tremor induced by bending hands backward)
  • Tests:

- Arterial blood gas shows elevated pCO2


  • CPAP (continuous positive airway pressure) device in moderate cases
  • Intubation/mechanical ventilation if the individual's breathing is compromised
  • Treat underlying cause if it exists, e.g., Guillain-Barre Syndrome
  • Discontinue and/or reverse any offending medications

  • This is a life-threatening medical emergency.  Immediate emergency medical treatment is needed. In cases of emergency in the United States, dial 911.