But recently, Valley, an assistant professor in the Division of Pulmonary and Critical Care at the University of Michigan, realized first-hand that the small device can produce less accurate oxygen readings in patients with dark skin.
One end of the device sends light through your finger while a sensor on the other side receives that light and uses it to detect the color of your blood; Bright red blood is highly oxygenated, while blue or violet blood is less. If the device is not calibrated for darker skin tones, skin pigmentation could affect the way light is absorbed by the sensor, resulting in defective oxygen readings.
In a person of color, the pulse oximeter could indicate that a patient’s oxygen levels are normal, suggesting that they may be discharged at home, but then their blood samples may show levels of oxygen. low oxygen, suggesting that they not only needed additional care, but also oxygen support.
“At the time, it was during the spring 2020 hike in Michigan, and we didn’t really raise that it was a race issue,” Valley told CNN. “We potentially thought this was a Covid problem, because that’s what we were flooding in with: hundreds of patients with Covid.”
Before the pandemic, most Valley patients at Michigan Medicine were white. But as the hospital treated more patients with Covid-19, Valley realized that many were black or brown patients from other overcrowded facilities.
Since then, Valley and colleagues have collected data on how often dust oximeters overestimate oxygen levels among their black and brown patients. Their findings suggest that black patients have almost three times the frequency that white patients experience blood oxygen levels below 88% despite showing between 92% and 96% in a pulse oximetry device. . A normal oxygen level is usually around 95% or more.
“At 92%, we don’t normally make clinical changes based on that, but if that 92% on a pulse oximeter means your oxygen levels are actually below 88%, well, that’s something about the which would make a clinical change. – if it’s about starting someone with oxygen or if it’s increasing their oxygen values, “Valley said.
“I still have issues to deal with when I have a black patient who has a pulse oximeter value that is marginal,” he said. “I think for a person at home, I think it increases the need to consider their symptoms.”
The experiences of Valley and his colleagues add to a growing body of research, dating back to the 1980s, that suggests that faulty pulse oximeter readings between black and brown patients may be a real problem. and life-threatening in health care. The latest study on defective pulse oximeter readings, published Monday in the journal JAMA Internal Medicine and in which Valley did not participate, found that among the more than 3,000 hospitalized patients receiving intensive care, black, Asian patients and Hispanics received less supplemental oxygen than white patients. Research published by Valley and colleagues last week in the medical journal BMJ found that black patients were more likely than white patients to have low blood oxygen levels in their blood readings, but not detected by pulse oximetry. This finding was based on data from the Veterans Health Administration, where pulse oximeter readings were combined with measurements of oxygen level from the blood draw. A separate study of about 7,000 patients with Covid-19, published earlier in May in the journal JAMA Internal Medicine, found that, compared to white patients, powder oximetry overestimated blood oxygen levels in an average of 1.7% among Asian patients, 1.2% among Asian patients. Black patients and 1.1% among Hispanic patients. This overestimation may have contributed to an unrecognized or delayed recognition of a patient’s eligibility to receive certain Covid-19 therapies.
“The consequences of negligence … have been revealed”
But the public has recently become more aware of this health disparity, and U.S. health officials have announced plans to investigate the accuracy of dust oximeters.
“It’s problematic,” Valley said.
“There was a study like ours done in 1990, but on a smaller scale in a single center. The problem from 1990 to 2020 is really a problem of dissemination and education. In the medical school, in the residency , on the scholarship, I did “I don’t know this problem,” he said. “It’s not that we now use pulse oximeters more often. I use a pulse oximeter every day, several times a day, all day in the intensive care unit, and that hasn’t changed in the last 10 years. It’s almost like he has his right hand. an intensive care unit. We depend on someone’s oxygen levels. “
The pulse oximeter was invented in 1974 by Japanese bioengineer Dr. Takuo Aoyagi, who died at the age of 84 in 2020; the same year, Covid-19, a disease whose symptoms are controlled by pulse oximetry, was declared a public health emergency of international concern.
Some experts believe that the pandemic takes more into account the limitations of the pulse oximeter when measuring oxygen levels between black and brown patients.
“I think the Covid-19 pandemic has exacerbated this problem,” said Rutendo Jakachira, Ph.D. student in the Department of Physics at Brown University, who studies racial disparities in pulse oximetry.
“People know that there is a problem with overestimating these oxygen saturation levels, especially in dark-skinned patients, but they did not appreciate the importance of this problem until the Covid-19 pandemic,” he said. to say. “The pandemic has seen an increase in the use of pulse oximeters in the hospital and at home, and therefore the consequences of neglecting problems with errors in these pulse oximeters have been revealed.”
Jakachira and his research adviser, Kimani Toussaint, argue that in the years following Aoyagi’s invention, not enough clinical trials were done to improve the device to ensure fairness between all demographics and skin.
“So one thing that needs to be done immediately is to improve the calibration tests,” Jakachira said, adding that currently, guidelines from the U.S. Food and Drug Administration recommend that these tests on powder oximeters include at least 10 healthy subjects who vary in age and gender with a range of skin pigmentations, of which two individuals or 15% of the group, “whichever is larger,” says the FDA guideline, have skin dark.
“This is probably not enough and not to draw statistical conclusions about disparities,” he said. “Therefore, using a more diverse population, calibration would be a great first step.”
Future of pulse oximetry
In April, the FDA released a new draft guideline recommending that companies that manufacture medical products develop and submit a “plan for racial and ethnic diversity” to the agency at the beginning of product development, and this plan should include the enrollment of various groups of people in their clinical clinic. essays. Jakachira, Toussaint and colleagues are developing non-invasive methods to make pulse oximeters more accurate in their blood oxygen readings for people with dark skin tones.
“In what we’re working on, we’re trying to mitigate skin tone issues by doing something interesting with light, but it’s a major challenge and that really highlights the need for diversity and inclusion,” said Toussaint, a professor. and teacher. senior associate dean of Brown University School of Engineering.
When dust oximeters send rays of light through your fingertips to measure blood oxygen levels, they are measuring the amount of oxygen that a certain molecule in the blood called hemoglobin has absorbed. It turns out that both melanin and hemoglobin absorb light at similar wavelengths and separating their relative contributions is what can be a challenge. Melanin is the substance that produces pigmentation in our skin, hair and eyes.
“Thus, melanin will overlap with the absorption properties of hemoglobin in the blood,” Toussaint said, which can lead to defective blood oxygen readings of the pulse oximeter, as different people have different amounts of melanin.
The approach Jakachira and Toussaint are taking in their search for a solution is to try to cancel out the effect that absorbed melanin can have on how pulse oximeters measure blood oxygen levels.
“This is something we believe would be a contribution, but perhaps translatable to other similar technologies that are not just pulse oximeters,” Toussaint said, adding that he could not share additional details of this work, as the team research is completing a patent application.
FDA advisors to discuss the accuracy of the pulse oximeter
The U.S. Food and Drug Administration plans to convene a meeting of its medical device advisors later this year to assess how dust oximeters can produce inaccurate oxygen readings among people of color.
A patient’s oxygen levels are sometimes called the “fifth vital sign” and there is growing anxiety about how this research on how inaccuracies in dust oximeters between people of color did not occur before, according to a editorial he published Monday in the journal JAMA Internal Medicine. .
“While the technical limitations of the pulse oximeter have been recognized for more than 30 years, research on the clinical implications of occult hypoxemia in patients with darker skin has been relatively (and distressing) recent,” explained Dr. Eric Ward , from the University of California, San Francisco and Dr. Mitchell Katz of NYC Health + Hospitals, wrote in their editorial.
They described an action plan for change.
“There are devices that work more equitably but have never been widely distributed,” Ward and Katz wrote. “Healthcare systems, including academic centers, are large-scale buyers of dust oximeters. If they commit to buying only devices that work in different skin tones, manufacturers would respond.”