Which range represents normal COHb levels?

Which range represents normal COHb levels?

• A. 0-1%
• B. 0-2%
• C. 2-4%
• D. 1-3%

Answer: (D)

Carboxyhemoglobin levels are the tiny fraction of hemoglobin that has carbon monoxide bound to it, and a small amount is normal due to endogenous production and minor environmental exposures. In healthy individuals, the baseline COHb is typically very low, but it can vary modestly with smoking or environmental factors. The range that best fits this normal variability is 1-3%, since it includes the small but common elevations seen in everyday life while staying below levels that would suggest significant exposure. A range like 0-1% is too strict for many people who have mild exposure, and 2-4% would push the upper limit into ranges often associated with noticeable exposure. Clinically, COHb rises well above these levels with meaningful exposure, so 1-3% best represents normal variation.

Carboxyhemoglobin levels are the tiny fraction of hemoglobin that has carbon monoxide bound to it, and a small amount is normal due to endogenous production and minor environmental exposures. In healthy individuals, the baseline COHb is typically very low, but it can vary modestly with smoking or environmental factors. The range that best fits this normal variability is 1-3%, since it includes the small but common elevations seen in everyday life while staying below levels that would suggest significant exposure. A range like 0-1% is too strict for many people who have mild exposure, and 2-4% would push the upper limit into ranges often associated with noticeable exposure. Clinically, COHb rises well above these levels with meaningful exposure, so 1-3% best represents normal variation.