Board Review: Carbon Monoxide Poisoning

Carbon Monoxide Poisoning 

33 year old healthy female presents to the ED via EMS after she was found unconscious in a burning house.  On your initial physical exam the patient is awake but confused.  She has normal vital signs with a pulse oximetry of 94%.  You suspect carbon monixide poisoning and send labs.  What is the minimal carboxyhemoglobin level that hyperbaric oxygen therapy would be indicated for this non-pregnant female?  (scroll down for the answer) 

A) 10%

B) 15%

C) 20%

D) 25%

E) 30%








The correct answer is D) 25%

A carboxyhemoglobin level >25% is an indication for hyperbaric oxygen therapy for any non-pregnant patient regardless of symptoms. 


Carbon Monoxide Pearls 

  • Colorless, odorless gas
  • Peak incidence in fall and winter
  • Normal physiologic levels are approximately 1% in nonsmokers but in smokers can reach as high as 10%
  • Standard pulse oximetry is unreliable as oxygen saturation readings will be artificially high 
  • Commonly used indications for hyperbaric oxygen treatment: pregnancy with carboxyhemoglobin level >15%, non-pregnant carboxyhemoglobin level  >25%, syncope, evidence of acute myocardial ischemia, altered mental status, seizure, coma, focal neurologic deficit 


1 Stapczynski, J. Stephan,, and Judith E. Tintinalli. Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 7th ed. New York, N.Y.: McGraw-Hill Education LLC., 2011.