Pulse Oximetry
Sonya Collins
Pulse oximeters send beams of light through the skin to measure the amount of oxygen in the blood. Health care providers who rely on the technology have long known that the tool can yield inaccurate readings for people with darker skin. But, in the absence of a more accurate tool, the devices have continued to be essential to their work. However, the COVID-19 pandemic brought about more urgent calls to right what is wrong with the technology.
“Overestimating oxygen saturation among certain populations prevents delivery of appropriate treatment for these populations. The most striking example was treatment eligibility for COVID-19 based on oxygen saturation thresholds,” said Adam J. Milam, MD, PhD, an anesthesiologist and medical director from the Office of Health Equity and Inclusion at Mayo Clinic in Phoenix, AZ. “The impact was delays in treatment initiation likely contributing to racial and ethnic disparities in morbidity and possibly mortality related to COVID-19.”
Due to ongoing disparities such as these and others, late last year, 25 attorneys general (AGs) joined forces to demand that FDA take swifter action to eliminate racial bias from pulse oximetry readers.
“An essential monitor that we use on a daily basis is not calibrated for a significant segment of the population,” Milam said. “These happen to be the same populations that have experienced profound health care disparities for decades.”
Demand for action
Because pulse oximeters work by shining light through skin, they may overestimate the oxygen saturation of people with darker skin. Research suggests melanin may absorb the light needed to provide an accurate reading. The degree of overestimation varies by device.
Oxygen saturation was a critical metric for disease severity and need for treatment with the first strain of COVID-19. During the pandemic, “pulse oximeter” became a household term and the devices flew off of pharmacy shelves.
In November 2022, in the wake of the pandemic, FDA’s medical devices advisory committee examined the underlying causes of inaccurate pulse oximeter readings for people who are not white. They called for clearer device labeling regarding the technology’s limitations and more rigorous testing of the devices moving forward. But, a year later, after not seeing any changes to the technology or guidance around it, 25 AGs signed a letter, written by California’s Rob Bonta, calling FDA to take urgent action based on the matter.
Their call was based on recent studies that further emphasize how much less effective these devices can be for people of color.
Mounting evidence, heightening stakes
A 2020 study published in NEJM found Black patients were nearly three times more likely than white patients to suffer from hypoxemia not detected by a pulse oximeter. In the July 2022 issue of JAMA Internal Medicine, researchers reported that Black and Hispanic patients faced statistically significant delays in getting necessary treatment for COVID-19, including supplemental oxygen.
The AGs’ letter cited concerns that racial bias built into pulse oximeters could perpetuate the racial disparities in maternal and infant mortality. The AGs also noted that predictive diagnostics currently in development—should it rely on racially biased pulse oximetry—they wrote, “could end up reproducing health disparities based on race.”
Pulse oximeters not tested on a variety of skin tones are the ones that are prone to giving inaccurate readings on people who are not white.
“This is an example of a greater problem,” Milam said. “Certain populations, such as racial and ethnic minority populations, sicker individuals, females, and individuals with low socioeconomic status, are underrepresented in clinical research so medical devices and therapies may not be generalizable nor effective in these populations.”
FDA’s website states the agency plans to publish a draft guidance on pulse oximeters this year. ■