Scientists are looking for solutions after studies showed pulse oximeters don't work well on people of color

Scientists are looking for solutions after studies showed pulse oximeters don’t work well on people of color

But more recently, Valley, an assistant professor in the University of Michigan’s Department of Pulmonary and Critical Care, realized firsthand that the small device It may lead to less accurate oxygen readings in dark-skinned patients.

One end of the device sends light through the finger while the sensor on the other side receives this light and uses it to detect the color of your blood; Bright red blood is highly oxygenated, while blue or purple blood is less. If the device is not calibrated for darker skin tones, skin pigmentation may affect how the sensor absorbs light, leading to false oxygen readings.

For a person of color, a pulse oximeter can indicate that the patient’s oxygen levels are normal, indicating that they can be drained home – but then their blood samples may show low levels of oxygen, indicating they just don’t need extra care But also to oxygen support.

“At the time, it was during the Spring 2020 Michigan surge, and we didn’t actually gather that this was a race issue,” Valley told CNN. “We thought this was probably a problem for Covid, because that’s what we’ve been inundated with – hundreds of patients with Covid.”

Before the pandemic, the majority of Valley patients at Michigan Medicine were white. But as the hospital treated more Covid-19 patients, Valley realized that many black or brown patients were coming from other overburdened facilities.

Since then, Valley and colleagues have collected data on how often the pulse oximeter overestimated oxygen levels among their black and brown patients. Their findings indicate that black patients have approximately three times the frequency of white patients with blood oxygen levels below 88% despite showing 92% to 96% on a pulse oximeter. The normal level of oxygen is usually around 95% or higher.

“At 92%, we don’t usually make clinical changes based on that, but if that 92% on the pulse oximeter means their oxygen levels are below 88%, well, that’s something I’m going to make a clinical change on — whether it comes to starting Someone is on oxygen, or whether that increases oxygen values,” Valley said.

“I still struggle with what I do when I have a black patient who has a marginal value of the pulse oximeter,” he said. “I think for the individual at home, I think it increases the need to take your symptoms into account.”

Valley and colleagues’ experiments add to a growing body of research — dating back to the 1980s — that indicates that defective pulse oximeter readings among black and brown patients can be a real and life-threatening problem in medical care.
The latest study of defective pulse oximeter readings, published Monday in the journal JAMA Internal Medicine in which Valley was not involved, found that among more than 3,000 hospital patients receiving intensive care, Asian, black and Hispanic patients received less supplemental oxygen than white patients. This was related to differences in pulse oximeter readings.
Research that Valley and colleagues published last week in the BMJ medical journal found that black patients had higher odds than white patients of having hypoxia observed in their drawn blood readings but not detected by pulse oximetry. This finding was based on data from the Veterans Health Administration where pulse oximeter readings were paired with oxygen level measurements from a blood draw.
A separate study of nearly 7,000 Covid-19 patients, previously published in May in the journal JAMA Internal Medicine, found that compared to white patients, pulse oximetry overestimated blood oxygen levels by an average of 1.7% among Asian patients, and 1.2% among patients. Black patients and 1.1% among Hispanic patients. This overestimation may have contributed to the unacknowledged or delayed recognition of a patient’s eligibility to receive some Covid-19 treatments.

‘Consequences of neglect… revealed’

But only recently has the public become more aware of this health disparity, and US health officials have announced plans to investigate the accuracy of pulse oximeters.

“It’s a problem,” Vale said.

“There was a study just like ours in 1990, but on a smaller scale in one center. The problem from 1990 to 2020 is really a publishing and education problem. In medical school, in residency, in fellowship, I didn’t know about this problem” . “It’s not that we use the pulse oximeter very often. I use the pulse oximeter every day, several times a day, all day in the ICU, and that hasn’t changed in 10 years. It’s like my right hand in the ICU. We rely on A person’s oxygen levels.

The pulse oximeter was invented in 1974 by Japanese bioengineer Dr. Taku Oyagi, who died at the age of 84 in 2020 – the same year Covid-19, a disease whose symptoms are monitored by pulse oximetry, was declared an emergency Public health of an international concern.

Some experts see the pandemic shedding more light on the limitations of pulse oximetry in measuring oxygen levels among black and brown patients.

“I think the COVID-19 pandemic has exacerbated this problem,” said Rotendo Jakashira, a PhD student in the Department of Physics at Brown University who studies racial disparities in pulse oximetry.

“People knew there was a problem with overestimating these oxygen saturation levels, especially in dark-skinned patients, but they didn’t appreciate the importance of this problem until the COVID-19 pandemic,” she said. “The pandemic has seen increased use of pulse oximetry in hospital and at home, and thus the consequences of neglecting issues with pulse oximeter errors have been revealed.”

Jakachira and its researcher Kimani Tosan argue that in the years since Oyagi’s invention, not enough clinical testing has been done to advise optimizing the device to ensure equality of all demographics and skin tone.

“Therefore, one thing that needs to be done right away is improved titration testing,” Jakashira said, adding that currently, guidelines from the FDA recommend such testing on a pulse oximeter on at least 10 healthy subjects that differ In age and gender with a range of skin pigmentations, of which two or 15% of the group—”whichever is greater” FDA guidelines indicate—have darker skin.

“This may not be enough and not to draw statistical conclusions about the disparities,” she said. “So, with a more diverse group, calibration would be a great first step.”

future pulse oximetry

In April, the U.S. Food and Drug Administration released draft new guidelines recommending that companies making medical products develop and submit the agency’s “racial and ethnic diversity plan” early in their product development, and that plan should include enrolling diverse groups of people in their clinical services. trials.
It's been a year since the Centers for Disease Control and Prevention declared racism a public health threat.  What now?
Jakashira, Toussaint and their colleagues are developing non-invasive methods to make pulse oximeters more accurate in blood oxygen readings for people with darker skin.

said Toussaint, professor and senior associate dean in Brown University’s School of Engineering.

When a pulse oximeter sends beams of light through the fingertips to measure oxygen levels in the blood, they measure how much oxygen a certain molecule in the blood called hemoglobin has absorbed. It turns out that both melanin and hemoglobin absorb light at similar wavelengths, separating their relative contributions can be challenging. Melanin is the substance that produces pigmentation in the skin, hair and eyes.

“So, the melanin will interfere with the absorption properties of hemoglobin in your blood,” Toussaint said, which could lead to defective blood pulse oximeter readings, because different people have different amounts of melanin.

The approach that Jakashira and Toussaint take in their search for a solution is to try to cancel out the effect that absorbed melanin can have on how the pulse oximeter measures oxygen levels in the blood.

“This is something that we think will certainly be a contribution but perhaps can be translated into other similar technologies which are not just pulse oximetry,” Toussaint said, adding that he could not share additional details on this work as the research team is currently completing the patent application.

FDA advisors debate the accuracy of pulse oximetry

The FDA plans to convene a meeting of medical device advisors later this year to assess how pulse oximeters can yield inaccurate oxygen readings among people of color.

A patient’s oxygen levels are sometimes called the “fifth vital sign,” and there is growing concern about how such investigations into how pulse oximetry inaccuracies may occur among people of color sooner, according to an editorial published Monday in the journal JAMA Internal Medicine.

“While the technical limitations of pulse oximetry have been recognized for more than 30 years, investigations into the clinical effects of occult hypoxia in dark-skinned patients have been relatively recent (and worrisome),” Dr. Eric Ward of the University of California, San Francisco and Dr. Mitchell Katz of the University of California, San Francisco and Dr. Mitchell Katz of Hospital + New York Health wrote in their editorial.

They described one action plan for change.

Ward and Katz wrote, “There are devices that function more fairly, but they have never been widely distributed.” “Healthcare systems, including academic centers, are large-scale buyers of pulse oximeters. If they stick to buying devices that only work across skin tones, manufacturers will respond.”

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