“It’s really shocking that the FDA has only issued an alert until 2021,” said Uché Blackstock, an emergency medicine physician and CEO of Advancing Health Equity. “And even in that alert last year, they didn’t even mention racial bias, race or racism.”
The issue raises broader concerns about bias as the technology becomes more integrated into health care, and about the government’s ability to counter it through regulation and oversight. Experts warn that disparate outcomes across racial groups could be made worse if the technology doesn’t work for all patients.
The Covid-19 pandemic has brought renewed attention to the devices, which commonly come in the form of a sensor on a patient’s fingertip.
Michael Sjoding, a pulmonary and critical care physician at the University of Michigan, conducted a study published in December 2020 in the New England Journal of Medicine that found that black patients between January and July 2020, as well as 2014 and 2015, were about three times more likely than whites to have undetected low blood oxygen levels. More than one in 10 black patients with an oxygen saturation reading of 92 to 96 percent on a pulse oximeter actually had levels below 88 percent when measured by blood tests.
Normal levels range from 95 to 100 percent, while levels below 88 percent are considered dangerous.
Experts also say the problem points to the need to update the guidance to compensate for the problem, as well as to diversify clinical trials.
The effect on attention is real, Sjoding said. “That level of difference, if it had been recognized and detected, would have changed the way we would care for a patient,” he explained. “It would give a patient more oxygen or potentially give a patient different treatments.”
known and unknown
Experts say that the faulty readings are a result of how light is absorbed by different skin tones. Pulse oximeters work by shooting light at a person’s skin and watching how much it bounces back, said Achuta Kadambi, a professor of engineering at the University of California, Los Angeles.
Darker skin reflects a smaller signal than lighter skin, which can corrupt the pulse oximeter reading, he said. Kadambi, who has darker skin, has run into similar problems with automatic soap dispensers, which also rely on light to activate.
“The laws of physics are against darker objects, which includes skin,” Kadambi said, adding that algorithms are one way to correct the problem.
But the research findings so far have limitations because not everyone has been differentiated by oximeter type, said Amira Mohamed, a professor at Albert Einstein College of Medicine. She also pointed out that generalizing by race can also be tricky.
“There are different types of black people,” Mohamed said. “I’m black myself and that doesn’t mean it’s going to work the same way on me as it would, for example, on my husband, who is a darker-skinned black person.”
Mohamed also says that the existing research was mostly done on people with fair skin and that future studies should focus on people most likely to be affected.
Current FDA Guidance recommends that manufacturers’ studies include a minimum of 10 people and “at least 2 dark-pigmented subjects” or 15 percent of the total group.
Some experts argue that the FDA needs to increase that group.
“Basically, you won’t have enough information about the accuracy of the device if you only test it on two people,” Sjoding said.
More specific FDA guidance on oximeters is warranted, said Ashraf Fawzy, a professor of medicine at Johns Hopkins University and lead author of a May study published in JAMA Internal Medicine which found that providers were more likely to underestimate the level of illness severity and delay treatment for black and Hispanic patients with covid-19.
Quicker action by the agency would have been helpful, Fawzy added. The FDA should consider adding a warning label to the devices, said Kimani Toussaint, an engineering professor at Brown University who is working on possible solutions.
Some experts, such as Blackstock, argue that oximeters should be taken off the market. Others, like Mohamed, say much more research is needed before drawing any conclusions.
“If we’re concerned about someone’s breathing or someone’s oxygen level, it’s not safe to completely rely on a pulse oximeter and we should always confirm that,” Mohamed said.
And fixing the problem on the devices themselves could be a chore.
The FDA spokesman said he is looking to expand the available data on the problem.
fund a prospective clinical trial to inform any change in recommendation. He hopes the investigation can resolve “sometimes conflicting data including non-public information” that manufacturers have provided.
Meanwhile, researchers at Brown University are working on using a single wavelength of light to bypass the skin. That research in healthy patients is in the early stages and has obtained results similar to those of commercial devices. The inaccuracies tend to be more frequent in sicker patients, said researcher Rutendo Jakachira, who works with Toussaint.
Scientists are also considering using sound as a possible replacement for light as a new method of reading blood oxygen levels.
Diversity of clinical trials
Meanwhile, with technology playing an ever-increasing role in health care, experts say clinical trials, in which people of color have long been underrepresented, are in need of an overhaul.
Legislators are aware of the problem. Last month, the House of Representatives passed FDA medical product user fee legislation that included language intended to bolster the diversity of clinical trials.
Adrian Aguilera, director of the Digital Health Access and Equity Laboratory at the University of California, Berkeley, said that in the absence of diverse participants, the trial results will not necessarily reflect what will occur in the real world.
Traditionally, rehearsals are held in person, requiring participants to show up at the location, which can create barriers for people with low incomes or those with inflexible jobs. Advocates want to use telehealth to attract a broader range of participants.
Companies should avoid “helicopter” investigation and instead take the time to build relationships with community organizations and people on the ground, Aguilera said.
“What this pulse oximeter situation exemplifies is that if you’re not thinking about bias and racism from the beginning, and you’re not intentionally doing so, it’s going to be built into the technology,” Blackstock said.