But several recent studies have raised concerns that people’s skin pigmentation may skew readings. In 2021, the Food and Drug Administration issued a warning about possible inaccuracies after a study found that the devices tended to overestimate the oxygen levels of black patients.
“That such a commonly used device could have any difference shocked me,” said Michael Sjoding, a University of Michigan pulmonologist who led the study. “I make a lot of medical decisions based on this device.”
The FDA convened a panel of experts to meet on Tuesday to discuss “continuing concerns” about the devices, recommendations for patients and doctors, and ways to assess accuracy.
Jeff Shuren, director of the FDA’s Center for Devices and Radiological Health, called racial disparities in such devices “of great public health significance” at the start of the meeting on Tuesday. He stressed the need to ensure that medical devices are safe and effective for all groups that use them.
Oxygen levels can also be measured by drawing blood from an artery in the wrist. This method is still the “gold standard” for accuracy, but it’s a bit trickier and more painful so can’t be used as often, said Leo Celi, a physician and researcher at MIT who studies oximetry. of pulse.
In comparison, pulse oximeters are faster, easier, and less invasive.
When the device snaps onto a finger, it sends two wavelengths of light into the skin, explained Rutendo Jakachira, a PhD student at Brown University who researches pulse oximetry. By measuring the amount of this light absorbed, the pulse oximeter estimates the amount of oxygen circulating in the blood.
The problem: Melanin — a natural pigment responsible for skin tone — also absorbs light, Jakachira said. And if the devices aren’t built with melanin in mind, the extra absorption can skew their readings.
A growing body of evidence suggests this appears to be affecting pulse oximeters on the market.
Sjoding’s study found that compared to white patients, black patients in hospital were almost three times more likely to suffer from “occult hypoxemia” – meaning their oxygen levels calculated from taken blood levels were dangerously low, but their pulse oximeter readings were still normal.
Follow-up research has shown that these mistakes can have real health impacts. When patients did not have their low oxygen level recognized, it meant delays in the treatment of COVID-19, less supplemental oxygen and one higher risk of organ failure and deathaccording to several recent studies.
All of these findings affected patients of color more often, according to the research. For many physicians, the idea that the tools they rely on could make racial gaps worse has come as a shock.
“These are fundamental vital signs that we use for patient care,” Sjoding said. “And so, if the device is even a little less accurate in a particular group of patients, that will have consequences.”
Small studies over the past few decades had hinted that skin tone could pose a challenge for the devices, but concerns have apparently “gone to one side”, said Johns Hopkins physician Ashraf Fawzy, who led one of the recent pulse oximeter studies. He and other doctors said they had never heard of racial shortcomings in pulse oximeters during their medical training.
But the COVID-19 pandemic has brought more attention to devices — and to issues of racial inequality in the healthcare system.
“Now we are more aware of the impact of health care disparities on people of color,” Fawzy said. “We are really motivated to solve these problems and make health care more equitable for everyone.”
Some device companies have pushed back on the idea that their pulse oximeters are less accurate for patients of color.
Masimo CEO Joe Kiani, whose company sells pulse oximeters to hospitals, said an internal review of their devices found no evidence of a significant difference in accuracy for black patients. He says other variables, such as a delay between pulse oximeter readings and blood draws, may have affected recent studies of pulse oximeter accuracy.
Yet others are developing new devices that aim to work better for different skin tones.
Jakachira and his adviser, Kimani Toussaint, are working on a modified pulse oximeter that still emits light into the skin to measure oxygen, but examines different properties of that light.
While technological solutions are still being worked on, experts say it’s important for healthcare workers to be aware that readings can be inaccurate. Sjoding said he began to rely less on pulse oximeter readings in his own practice. It still uses them, but as a data point which may not be perfect.
Some experts hoped updated FDA testing guidelines — like more specific rules about who should be included in studies — could help ensure future pulse oximeters work for everyone. The current standards suggest that at least 15% of a test group should have “darkly pigmented” skin.
Switching devices like the pulse oximeter can be an “uphill battle,” said A. Ian Wong, a pulmonary critical care physician at Duke University – but he thinks it’s a necessary step to providing care. equal to all patients.
“Medicine is a bit of an art and a science,” Wong said. “It’s more than a doctor’s practice; they are also the tools you use.
The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute Department of Science Education. The AP is solely responsible for all content.