Interpretation of Carboxyhemoglobin Blood Concentration

Measurement of the carboxyhemoglobin (CO-hemoglobin complex) concentration can provide useful information after a fire or smoke inhalation.

Carboxyhemoglobin Level (percent hemoglobin saturation)	Interpretation
0.5% to 1.5%	normal nonsmoker
4% to 5%	cigarette smoker, 1-2 packs per day
8% to 9%	cigarette smoker, > 2 packs per day
< 10%	may impair cognitive function in nonsmoker; may aggravate existing heart disease
10% to 30%	dizziness, headache, nausea, vomiting
> 25%	admit to hospital
> 30%	moderate poisoning; can be fatal with comorbid condition (especially heart disease)
> 40%	severe poisoning
> 50%	coma, shock, may be fatal in healthy person
> 80%	rapidly fatal

where:

• fraction of hemoglobin saturation = (percent hemoglobin saturation) / 100

Limitations:

• The level measured in the hospital may not reflect the peak concentration at the scene, especially if oxygen therapy has been given.

• As indicated in 33.09.01, symptoms may be a better indicator of clinical severity than the carboxyhemoglobin level.

• A person with severe comorbid disease will be symptomatic at lower carboxyhemoglobin concentrations than a young, healthy individual.

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Purpose: To interpret the significance of a patient's carboxyhemoglobin level.