The Daily UbuntuThread 03 · Racialized but Human · September 25, 2026
When the device doesn't see the skin
Pulse oximeters can overestimate blood oxygen in people with darker skin. A bias hidden in an ordinary object.
1 · The scene
In a pharmacy in Laval, a woman buys a small oximeter for her father, who has been coughing for a week. That evening, the screen shows 95%. Everyone breathes a sigh of relief.
But her father is still short of breath, and his daughter is not at ease. She calls Info-Santé, which advises her not to rely on the number alone. "Look at him, not just at the device." They go to get him checked.
Original vignette
2 · The documented case
Pulse oximeters and darker skin
A pulse oximeter is the small clip you put on your fingertip to estimate the oxygen in your blood. It works with light that passes through the skin. On December 17, 2020, a University of Michigan team led by pulmonologist Michael Sjoding published in the New England Journal of Medicine a comparison between these devices and blood tests, which are more reliable. The result: in Black patients, a lack of oxygen went undetected nearly three times as often as in white patients.
No one intended this bias. But a device designed and calibrated mostly on lighter skin can give false reassurance at the very moment action is needed. Health Canada now informs the public that these readings may be less accurate in people with darker skin: a device can display 94% when the real level is 88%.
Naming this bias already opens the door to change. Researchers are asking that devices be tested on all skin colours, and manufacturers say they are looking for solutions. Fair care begins when we ask whom a tool was designed for.
3 · The voice
“It's not as if the machine decided to be biased.”
4 · The question
Which tools in our everyday lives were designed for "everyone" without everyone being invited to the table?
Sources
- M. W. Sjoding et al., "Racial Bias in Pulse Oximetry Measurement," New England Journal of Medicine, December 17, 2020. www.nejm.org
- University of Washington, Alliance for Pandemic Preparedness, summary of the study, December 18, 2020. depts.washington.edu
- Health Canada, "Pulse oximeters: Consumers," updated December 30, 2022 (French version). www.canada.ca
- C&EN (American Chemical Society), "Pulse oximeters are less accurate for Black people," vol. 99, no. 1. cen.acs.org
- Bridge Michigan, interview with Michael Sjoding, November 11, 2022. bridgemi.com
Every figure on this page links to a verifiable public source.
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