Whenever you go to the doctor’s office—be it your primary care physician or an urgent care clinic—there are a few things that always happen. They take your temperature and blood pressure, get your height and weight, and measure your oxygen levels. While all of us have had the little finger contraption on to measure our O2 levels at one point or another, do you really know how it works?
As it turns out, scientists have long known that pulse oximeters—the devices that clip onto your pointer finger to read your oxygen levels—can yield inaccurate results on darker skin tones. But a recent study conducted by the medical journal Epic Research has revealed that these overestimations are more significant than once believed.
How Inaccurate Are The Readings?
In search of more concrete answers on how pulse oximeters read the oxygen levels of darker skin tones, Epic Research gathered data from over 13,000 across U.S. hospitals between January 2016 and November 2023, and the findings revealed that Black patients are 31.9 percent more likely than white patients to have oxygen readings that overestimate their levels by at least 4 percent.
What does this mean for treatment, then? As the researchers on the study explained, “providers often order supplemental oxygen or other treatment when oxygen saturation drops below 88%,” but if a reading falsely shows a patient’s oxygen levels to be much higher than 88 percent, “there may be a delay in potentially life-saving treatment, which could result in significant risk to the patient.”
The study also found that 24.7 percent of Black patients had pulse oximeter readings that were at least 5 percent higher than the oxygen levels in their blood gas results, whereas the discrepancy for white patients was only 19 percent. Why does this happen? As the study explains, pulse oximeters use light beams sent through one’s fingers to estimate their oxygen levels, but years of research has proven that pigmentation of the skin can impact light absorption and yield inaccurate results.
In terms of what the results mean for the field as a whole, “We weren’t surprised,” said Dr. Roderick King, senior vice president and chief diversity, equity and inclusion officer at the University of Maryland Medical System (one of the authors of the Epic Research report). “We’ve noticed even before Covid that the pulse ox inaccuracy was there for darker-skinned patients. But what was the most dramatical or most impactful part of this article, was that we could quantify using a large dataset, how much it was inaccurate. It drives home the importance of understanding how we look at equity and patient care, or health equity.”
