It can! In persons with darkly pigmented skin, pulse oximeters may overestimate arterial oxygen saturation, such that some individuals with oxygen saturation within an acceptable range by pulse oximetry may actually be hypoxemic by arterial blood measurement.^1-3

A 2020 study involving 2 large patient populations with oxygen saturations of 92-96% by pulse oximetry, found occult hypoxemia (<88% arterial oxygen saturation) in ~12% of patients who were Black vs ~4% of those who were White. Black individuals were 3 times more likely to have occult hypoxemia than White patients.¹

Overestimation of oxygen saturation—particularly at low arterial oxygen saturation— by pulse oximetry in dark-skinned individuals has been previously reported by several studies, although some have not found significant differences at normal saturations, and the degree of discordance may vary among various pulse oximeters.^2,3

The reason for the apparent discrepancy between oxygen saturation measured by pulse oximetry vs arterial blood sample in those with dark skin is unclear. Some have suggested “pulse oximeter optical factors” and theorized that provision of correction factors, tables, or even built-in user -optional adjustments may be necessary.²

Given the frequent use of pulse oximetry for medical decision making in Covid-19, these studies should serve as a cautionary note when interpreting oxygen saturation by pulse oximeter in dark-skinned patients with Covid-19.

Bonus Pearl: Did you know that falsely-LOW oxygen saturation has been reported with blue and green nail polish but not red?⁴

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References

1. Sjoding MW, Dickson RP, Valley TS. Racial bias in pulse oximetry measurement. N Engl J Med 2020;383:2477-78. https://pubmed.ncbi.nlm.nih.gov/33326721/
2. Bickler PE, Feiner JR, Severinghaus JW. Effects of skin pigmentation on pulse oximeter accuracy at low saturation. Anesthesiology 2005;102:715-9. https://pubs.asahq.org/anesthesiology/article/102/4/715/7364/Effects-of-Skin-Pigmentation-on-Pulse-Oximeter
3. Zeballos RJ, Weisman. Reliability of noninvasive oximetry in Black subjects during exercise and hypoxia. Am Rev Resp Dis 1991;144:1240-4. https://www.atsjournals.org/doi/pdf/10.1164/ajrccm/144.6.1240
4. Cote CJ, Goldstein EA, Fuchsman WH. The effect of nail polish on pulse oximetry. Anesth Analg 1988;75:683-6. https://pubmed.ncbi.nlm.nih.gov/3382042/

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