Which factor has minimal impact on pulse oximeter accuracy among the following?

Which factor has minimal impact on pulse oximeter accuracy among the following?

• A. Indigo carmine administration
• B. Indocyanine green administration
• C. Methylene blue administration
• D. Fetal hemoglobin presence

Answer: (D)

Pulse oximetry determines oxygen saturation by comparing how much red light (about 660 nm) and infrared light (about 940 nm) is absorbed as light passes through tissue, relying on the different absorption of oxygenated versus deoxygenated hemoglobin. Anything that changes absorption at those two wavelengths can distort the readings, because the device relies on a specific ratio of signals. Dyes such as Indigo carmine, Indocyanine green, and Methylene blue absorb significantly at or near these wavelengths, so their presence can alter the red and infrared signals and lead to inaccurate SpO2 values. Fetal hemoglobin, however, has absorption characteristics essentially the same as adult hemoglobin at these wavelengths, so its presence does not meaningfully change the ratio the oximeter uses. Hence, fetal hemoglobin has minimal impact on pulse oximeter accuracy.

Pulse oximetry determines oxygen saturation by comparing how much red light (about 660 nm) and infrared light (about 940 nm) is absorbed as light passes through tissue, relying on the different absorption of oxygenated versus deoxygenated hemoglobin. Anything that changes absorption at those two wavelengths can distort the readings, because the device relies on a specific ratio of signals. Dyes such as Indigo carmine, Indocyanine green, and Methylene blue absorb significantly at or near these wavelengths, so their presence can alter the red and infrared signals and lead to inaccurate SpO2 values. Fetal hemoglobin, however, has absorption characteristics essentially the same as adult hemoglobin at these wavelengths, so its presence does not meaningfully change the ratio the oximeter uses. Hence, fetal hemoglobin has minimal impact on pulse oximeter accuracy.