Like many people who are Black, Kimani Toussaint was concerned when he learned that the pulse oximeters relied on so heavily by physicians to treat and monitor Covid-19 patients didn’t work as well on darker-skinned patients.
Unlike many people who are Black, he could do something about it. Toussaint is an optics expert whose lab at Brown University creates precision techniques to image and assess biological tissues. This was a problem he was built for.
Now Toussaint and his doctoral student Rutendo Jakachira are literally using tricks of the light to develop a next-generation pulse oximeter they hope will work well on patients of all skin tones, not just those with lighter skin.
Meanwhile, Valencia Joyner Koomson, a Black associate professor of electrical and computer engineering at Tufts University, is working on a different solution: “smart” oximeter devices that are adaptable and less sensitive to skin tone.
Both Toussaint and Koomson are rarities; only 5% of America’s engineering workforce is Black, and less than 2% are Black women. The fact that these Black engineers are leading the charge on fixing a disparity that’s been in place and largely ignored by white scientists for decades is not lost on them. To Toussaint, it’s a serious case of scientific myopia — and a clear example of what’s lost when most scientists are white.
“We can’t say anything about anyone’s intent, but we can talk about the structure of science being one in which you don’t have broad diversity, and then you have these blind spots,” Toussaint said. “The issue of pulse oximeters is absolutely a poster child for having diversity in science.”
Pulse oximeters — extremely basic and ubiquitous medical devices — do not work as well on people with darker skin because melanin in skin can interfere with the absorption of light the clip-on devices use to measure the amount of oxygenated blood in a person’s finger. The problem can lead to readings in those with darker skin that mask possibly dangerous low oxygen levels. When Toussaint’s wife, an epidemiologist, told him about the problem early in the pandemic, he was stunned.
“I was like, what do you mean no one solved this?” he told STAT. “I said, ‘Wait a minute, it’s an approved device and no one looked at this?’” The devices had been calibrated largely on patients with lighter skin and many were indeed approved by the Food and Drug Administration despite their limitations on those with dark skin. In February 2021, the agency issued a safety communication alerting physicians and consumers that the devices may not be accurate in all patients.
Koomson, an expert on using micro- and nanoscale systems to create smart biosensors for low-cost health monitoring devices, has been concerned about the ability of pulse oximeters to work on patients with dark skin for more than a decade, but until recently has had trouble attracting attention to the problem, or research funding to help fix it.
“In all the textbooks I reviewed, they never mention melanin absorption. The fact that was being left out concerned me,” she said. Koomson had also heard from physicians working in Africa who were frustrated there was so little clinical trial and device testing data available for African populations.
Koomson has received funding to study how to better monitor oxygenation in tissues, a much harder task than measuring it in blood, and always kept in mind the importance of creating devices that worked on all skin tones, she said. But funding agencies had little interest in improving current devices, she said: “Getting funding to work on pulse oximeters is difficult because it’s such a well-established technology.”
The fact that the devices work less well on people with darker skin has been known for decades. Early devices created by Hewlett Packard worked very well on most people but were made obsolete by the newer, more compact devices in use today. Many in engineering and medicine have long accepted the higher rate of errors that occurred in patients with darker skin and felt they were not clinically relevant.
“There wasn’t enough data to show these errors affected clinical treatment. People could say, this is within an acceptable margin of error,” Koomson said.
But a flood of new research is challenging that view. A University of Michigan study that captured widespread attention in December 2020 showed that Black patients were three times more likely than white patients to have “hidden hypoxia” — dangerously low oxygen levels that pulse oximeters did not detect. Subsequent studies showed that patients with darker skin receive less supplemental oxygen during stays in the intensive care unit and that hidden hypoxia is a problem in patients with darker skin even when they are not in the ICU. Another study showed darker-skinned patients were less likely to receive cutting-edge Covid-19 treatments.
Since oxygen is so vital to survival and organ health, researchers say issues with pulse oximeters may contribute to poorer outcomes such as death and organ failure in patients with darker skin.
That research “has brought this to the forefront,” Koomson said. She’s now working on devices that use off-the-shelf components and, unlike current devices, use lights and sensors that can be adapted for patients of different skin colors. The main challenge, she said, is not in creating the devices, but in testing them, since that must be done in very ill patients.
Adapting technology to skin color is not a new idea, she said; it’s used in the cosmetic industry, for example, where lasers for hair removal are adjusted to prevent scarring in those with darker skin, and in photography. “When you take a photo, you adjust the light to get an accurate picture,” she said. “That’s what we’re doing — adjusting the light.”
Like Toussaint, Koomson agrees that the problem with pulse oximeters highlights the need for greater diversity in engineering. “You hear people saying, ‘I decided to go into breast cancer because it affected someone close to me,’” she said. “The problems we seek to address are ones that are near and dear to us.”
Koomson did not come from a scientific or engineering family. Her parents, who grew up on former sharecropping plantations in North Carolina, migrated to Washington, D.C., for work opportunities. Her mother is a hairdresser and her father is retired military. What drew her to science, she said, were programs run by Howard and other universities for inner-city high school kids. When she started college at the Massachusetts Institute of Technology, she said, “I felt I had stepped into a whole other world. It was wonderful.”
Her family has a history of civil rights activism, and had taken part in the Greensboro, N.C., sit-ins at Woolworth stores. Koomson is not only working in the lab, but engaging with senators and others to push for action on improving pulse oximeters. “I feel like this is my opportunity to engage in activism,” she said.
When he learned of the problem with pulse oximeters in 2020, Toussaint, a professor and senior associate dean of engineering at Brown, set right to work. Jakachira, a second-year doctoral student in physics, took over when she joined Toussaint’s lab last year.
Toussaint has worked on all manner of problems in applying optics to medicine, and this one is not easy to fix, he said. “It’s an optics challenge,” he said. But he thinks it is tractable and did not hesitate to start working on it due to his skill set and the importance of the issue to the Black community. “To me, it was an amazing alignment of circumstances.”
Toussaint had always been interested in science as a child — taking apart objects and trying, not always successfully, to put them back together — but hadn’t realized science could be a career and rarely saw people working in science who looked like him. “When you don’t see others who look like you in a field, you have questions about belonging,” he said.
He was encouraged to be a doctor, but hospitals and needles turned him off. Drawn to physical sciences, Toussaint attended the University of Pennsylvania and then earned both a master’s degree and a Ph.D. in electrical engineering at Boston University. Almost all of his science professors were white, but he sought out the few Black mentors he could find. “When I saw Black scientists, I gravitated to them and stayed in contact,” he said.
The physical sciences, he said, have long been less welcoming to students of color. Now that people in those fields have pledged to do better in response to the Black Lives Matter movement, he’s watching to see what actual change will occur. He’s doing his part, he said, by mentoring students like Jakachira.
Originally from Zimbabwe, she defied the wishes of her parents who hoped she’d become a doctor, and chose physics instead. But she said she almost left her graduate program in physics because the experiments she was considering conducting in condensed matter physics — very pure academic research projects — weren’t sparking her interest.
Then she found the pulse oximeter project and hasn’t looked back. “This project kept me in my Ph.D. program,” she said. “It’s very motivating to be working on a project that could directly impact people in my community.” She’s even more convinced that it’s important that she’s where she is, working as a Black physicist. “We definitely are rare,” said Jakachira, “and we bring a different perspective.”
What she and Toussaint are doing — it’s all very technical and a little bit secret since they are applying for a patent — is playing with electrical properties of light so the device’s sensors aren’t thrown off by melanin. Jakachiri is using off-the-shelf components and LED lights like those used in traditional pulse oximeters to build the devices because they are cheap and stay cool to the touch. Their experimental device uses just one wavelength of light, not two like most pulse oximeters, but the researchers think it will still be more precise.
Jakachira has tested the shoebox-sized device on volunteers and presented her early results at an international conference on optics. The two are now working with colleagues at Brown’s medical school to plan clinical trials of the device on patients who are sicker and have a wide range of skin colors. “We need to study this not in healthy volunteers, but in people who might be hypoxic,” Toussaint said.
Clinical trials will likely take months, he said, and could lead to improvements in the device if it doesn’t work as well as expected. If all goes well, he’ll look into partnerships to miniaturize the technology and create devices for consumer use. That process can normally take a decade or longer, but Toussaint is hoping for a faster track. “Normally we are much more academic. We do research and publish papers and don’t think about the device aspect,” said Toussaint. “But this is a rather urgent area of research.”
The work being done by Koomson, Toussaint, and Jakachira is of critical importance, say physicians who have been frustrated to learn that the devices work less well on patients with darker skin and upset that fact was not part of their medical training.
“2020 was the first time I learned about this, and I trained in the Bronx,” said Utibe Essien, a Black assistant professor of medicine at the University of Pittsburgh who has been practicing for about a decade. “The time is now to go beyond describing these disparities. It’s time to start intervening.”
Many clinicians say they are now approaching pulse oximeter readings from patients with darker skin with more caution or turning to more painful arterial blood draws, something Thomas Valley, a University of Michigan pulmonologist who is one of the leading researchers on the problems with pulse oximeters, calls “suboptimal workarounds” that only add to health disparities.
“There is only one true solution to the problem of inaccurate pulse oximeters and that is to have better pulse oximeters that can be trusted regardless of the color of one’s skin,” Valley told STAT, applauding the work underway at Brown and Tufts. If device manufacturers are not addressing these issues, he added, “then we need researchers to take the lead.”
In June, FDA officials said they planned to convene a public meeting later this year to discuss whether further regulatory action over use of the devices is needed.
Toussaint isn’t waiting. “If we can solve this, it will be amazing,” he said. “I’m beside myself.”