How do carboxyhemoglobin levels in the blood correspond to the clinical presentation of smoke inhalation injury?

Updated: Oct 15, 2021
  • Author: Keith A Lafferty, MD; Chief Editor: Joe Alcock, MD, MS  more...
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Carboxyhemoglobin levels in the blood and the corresponding clinical manifestations are as follows [1] :

  • 0-10% - Usually no symptoms

  • 10-20% - Mild headache, atypical dyspnea

  • 20-30% - Throbbing headache, impaired concentration

  • 30-40% - Severe headache, impaired thinking

  • 40-50% - Confusion, lethargy, syncope

  • 50-60% - Respiratory failure, seizures

  • Greater than 70% - Coma, death

Blood carboxyhemoglobin levels may underestimate the degree of CO intoxication because of oxygen administered to the patient before arrival to the hospital. Smokers may have baseline levels up to 5-10% and may experience more significant CO poisoning for the same level of exposure as nonsmokers. Finally, correlation between carboxyhemoglobin levels and eventual neurologic outcome is poor.

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