Pulse Oximeters Flip From Over- to Underestimating Oxygen — SkimNews
Get the Health newsletter
Daily health & science — research, biotech, public health, the studies worth knowing. Free.
- Johns Hopkins researchers found pulse oximeters at their hospital gradually shifted from overestimating to underestimating blood oxygen over five years, with inaccuracies worse in patients of color, per a retrospective study published in the Annals of the American Thoracic Society.
- The FDA-funded EquiOx study, published earlier in 2025, found the opposite of what it set out to investigate — pulse oximeters were underestimating, rather than overestimating, blood oxygen levels — a result authors and outside commentators struggled to justify.
- Masimo, manufacturer of the oximeters used in the Hopkins study, said it was "unaware of any sensor, software, or manufacturing changes during the study period" that would explain the reported shift, and pointed to two company-supported studies finding no skin-tone-based efficacy differences.
- Thomas Valley, a University of Colorado Anschutz pulmonologist involved in a seminal 2020 NEJM paper on pulse oximeter bias, compared the devices to a broken clock: if clinicians knew they were consistently five minutes slow they could compensate, but "it's unclear whether that metaphorical clock is running fast or slow."
- An Emory University prospective study found inaccurate readings were not fully explained by skin tone alone — conditions like anemia, cardiovascular disease, and liver disease, more common in patients of color, also likely affect results, said Emory ICU physician Sivasubramanium Bhavani.
- Hopkins author Jack Iwashyna said it is "not at all clear these things are fit for use in the way that we're using them," given that both overestimation (risk of missed treatment) and underestimation (risk of unnecessary care or longer hospitalization) carry clinical consequences.
Why it matters: Clinicians lose the ability to compensate for known biases because the devices' errors are now unpredictable — overestimation risks missing needed care, while underestimation risks unnecessary treatment or longer hospital stays. Hopkins author Jack Iwashyna said it is "not at all clear these things are fit for use in the way that we're using them."
Ask SkimNews
