Which of the following is most likely to be associated with a falsely elevated SaO2 as measured by pulse oximetry?

Which of the following is most likely to be associated with a falsely elevated SaO2 as measured by pulse oximetry?

• A. Hemoglobin F
• B. Carboxyhemoglobin
• C. Bilirubin
• D. Fluorescein dye

Answer: (B)

Pulse oximetry estimates oxygen saturation by analyzing light absorption at two wavelengths to distinguish oxyhemoglobin from deoxyhemoglobin. If carbon monoxide is present, it binds to hemoglobin to form carboxyhemoglobin, and CO-bound hemoglobin absorbs light in a way that resembles oxyhemoglobin at the wavelengths used by standard pulse oximeters. Because the device interprets the signal as highly oxygenated blood, the reading appears falsely elevated even though the blood’s oxygen-carrying capacity is reduced and tissues may be hypoxic. To truly know the oxygen status in this scenario, a co-oximeter is needed, as it can differentiate carboxyhemoglobin from oxyhemoglobin and other species. Other listed factors do not produce this specific overestimation of SpO2 in the same way.

Pulse oximetry estimates oxygen saturation by analyzing light absorption at two wavelengths to distinguish oxyhemoglobin from deoxyhemoglobin. If carbon monoxide is present, it binds to hemoglobin to form carboxyhemoglobin, and CO-bound hemoglobin absorbs light in a way that resembles oxyhemoglobin at the wavelengths used by standard pulse oximeters. Because the device interprets the signal as highly oxygenated blood, the reading appears falsely elevated even though the blood’s oxygen-carrying capacity is reduced and tissues may be hypoxic. To truly know the oxygen status in this scenario, a co-oximeter is needed, as it can differentiate carboxyhemoglobin from oxyhemoglobin and other species. Other listed factors do not produce this specific overestimation of SpO2 in the same way.