Faulty oxygen readings could be behind Covid-19 toll on people of color
« It’s really shocking that it wasn’t until 2021 that the FDA issued an alert, » said Uché Blackstock, emergency physician and CEO of Advancing Health Equity. « And even in that alert last year, they didn’t even mention racial bias or race or racism. »
The issue raises broader concerns about biases as technology becomes more integrated into health care and the government’s ability to counter them through regulation and oversight. Experts warn that disparate outcomes between racial groups could get worse if the technology doesn’t work for all patients.
Researchers identified problems with pulse oximeters years ago, with small studies indicating misreadings in people of color in 1990, 2005 and 2007.
The Covid-19 pandemic has brought renewed attention to the devices, which typically take the form of a sensor at the 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 which found that black patients between January and July 2020 as well as 2014 and 2015 were approximately three times more likely than whites to have low blood oxygen levels go unnoticed. More than one in 10 black patients with an oxygen saturation reading of 92-96% on a pulse oximeter actually had levels below 88% when measured by blood tests.
Normal levels range from 95-100%, while levels below 88% are considered dangerous.
Experts also say the issue underscores the need for updated guidelines to offset the problem, as well as diversifying clinical trials.
The effect on care is real, Sjoding said. “That level of difference, if recognized and detected, would have changed the way we would care for a patient,” he explained. “You would be giving a patient more oxygen or potentially giving a patient different treatments.”
known and unknown
Experts say the erroneous readings are a result of how light is absorbed on different skin tones. Pulse oximeters work by shining light onto a person’s skin and observing the amount of bounce, said Achuta Kadambi, an engineering professor at the University of California, Los Angeles.
Darker skin returns a smaller signal than lighter skin, which can corrupt the pulse oximeter reading, he said. Kadambi, who is darker-skinned, has encountered similar issues with automated soap dispensers, which also rely on light to activate.
« The laws of physics are against darker objects, which include skin, » Kadambi said, adding that algorithms are one way to fix the problem.
But the research results so far have limitations because they haven’t all been differentiated by type of oximeter, said Amira Mohamed, a professor at the Albert Einstein College of Medicine. She also noted 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 on me as it does on, say, my husband, who is darker-skinned black. »
Mohamed also says that existing research has been conducted primarily on white-skinned people and that future studies should focus on those most likely to be affected.
Current FDA guidelines recommend that manufacturers’ studies include a minimum of 10 people and « at least 2 dark-pigmented subjects » or 15% of the entire group.
Some experts say the FDA needs to expand this pool.
« 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 guidelines on oximeters are warranted, said Ashraf Fawzy, professor of medicine at Johns Hopkins University and lead author of a study published in May in JAMA Internal Medicine that found providers were more likely underestimating the severity of the disease and delaying treatment. Black and Hispanic Covid-19 patients.
Quicker action by the agency would have been helpful, Fawzy added. The FDA should consider adding a warning label to devices, said Kimani Toussaint, a Brown University engineering professor who is working on potential fixes.
Some experts, like Blackstock, argue that oximeters should be taken off the market. Others, like Mohamed, say there needs to be a lot more research before drawing any conclusions.
« If we’re concerned about someone’s breathing or oxygen level, it’s not safe to rely entirely on a pulse oximeter and we always need to confirm that, » Mohamed said.
And solving the problem in the devices themselves could be a heavy burden.
The FDA spokesperson said he was looking to expand the data available on the issue by
fund a prospective clinical trial to inform any change in recommendation. He hopes the research can sort through “sometimes conflicting data that includes non-public information” that manufacturers have provided.
Meanwhile, researchers at Brown University are working on using a single wavelength of light to contour the skin. This research on healthy patients is in its early stages and has yielded similar results to commercial devices. Inaccuracies tend to be more common in the sickest patients, said researcher Rutendo Jakachira, who works with Toussaint.
Scientists are also considering using sound as a potential substitute for light as a new method of reading blood oxygen levels.
Diversity of clinical trials
Meanwhile, with technology playing an increasingly important role in health care, experts say clinical trials, in which people of color have long been underrepresented, need an overhaul.
Lawmakers are aware of the problem. Last month, the House passed legislation on user fees for FDA medical products that included language aimed at bolstering diversity in clinical trials.
Adrian Aguilera, head of the Digital Health Equity and Access Lab at the University of California, Berkeley, said that in the absence of various participants, the results of the trial will not necessarily reflect what will happen in the real world. .
Trials are traditionally conducted in person, requiring participants to travel to the location, which can create barriers for people on low incomes or those with inflexible jobs. Proponents want to use telehealth to attract a wider range of participants.
Companies should avoid « helicopter » research and instead take the time to build relationships with community organizations and people on the ground, Aguilera said.
« What this pulse oximeter situation illustrates is that if you’re not thinking about prejudice and racism from the start, and you’re not intentional about it, it’s going to get baked into the technology, » said said Blackstock.