Pulse oximeters faulty, not as accurate on people of color
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The Food and Drug Administration will convene an advisory panel to investigate pulse oximeters after readings weren't as accurate on dark-skinned people.
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Pulse oximeters didn't work as well on people of color.
Dr. Thomas Valley frequently clamps a pulse oximeter on a new patient's finger in the intensive care unit at Michigan Medicine in Ann Arbor, one of many devices he uses to gauge their health and what course of care they might require, whether they are a child having seizures, a teenage car accident victim, or an older person with Covid-19.
Valley, an assistant professor in the Division of Pulmonary and Critical Care at the University of Michigan, recently discovered firsthand that the small device may produce less accurate oxygen readings in patients with dark skin.
What's the issue?
The device's one end sends light through the finger, while 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 purplish blood is less so. If the device is not calibrated for darker skin tones, skin pigmentation may affect how light is absorbed by the sensor, resulting in inaccurate oxygen readings.
On a person of color, the pulse oximeter may show that a patient's oxygen levels are normal, indicating that they can be discharged home; however, their blood samples may show low oxygen levels, indicating that they require not only additional care but also oxygen support.
"At the time, it was during the spring 2020 surge in Michigan, and we didn't actually put together that this was a problem of race," Valley told CNN. "We thought potentially, this was a problem of Covid because that's what we were being inundated with -- hundreds of patients with Covid."
What did the findings reveal?
Prior to the pandemic, the majority of Valley's Michigan Medicine patients were White. However, as the hospital treated more Covid-19 patients, Valley realized that many were Black or brown patients who had been transferred from other overcrowded facilities.
Valley and his colleagues have since gathered data on how frequently pulse oximeters overestimate oxygen levels in their Black and brown patients. According to their findings, Black patients are nearly three times more likely than white patients to have blood oxygen levels less than 88% despite showing 92% to 96% on a pulse oximetry device. A normal oxygen level is usually at around 95% or higher.
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"At 92%, we typically don't make clinical changes based on that, but if that 92% on a pulse oximeter means that their oxygen levels are actually below 88%, well, that is something that I would make a clinical change about -- whether it's starting someone on oxygen, or whether it's increasing their oxygen values," Valley said.
"I still struggle with what to do when I have a Black patient who has a pulse oximeter value that's marginal," he said. "I think for an individual at home, I think it heightens the need to take your symptoms into account."
Valley and his colleagues' experiences add to a growing body of research – dating back to the 1980s – indicating that inaccurate pulse oximeter readings among Black and brown patients can be a real and life-threatening problem in medical care.
Faulty pulse oximeter readings
The most recent study on faulty pulse oximeter readings, published Monday in the journal JAMA Internal Medicine, found that among more than 3,000 hospitalized patients receiving intensive care, Asian, Black, and Hispanic patients received less supplemental oxygen than White patients, which was associated with differences in their pulse oximeter readings.
Valley and his colleagues discovered that Black patients had a higher risk than White patients of having low blood oxygen noted in their blood-drawn readings but not detected by pulse oximetry, according to research published last week in the medical journal BMJ.
This discovery was based on data from the Veterans Health Administration in which pulse oximeter readings were paired with oxygen level measurements obtained by drawing blood.
A separate study of approximately 7,000 Covid-19 patients, previously published in the journal JAMA Internal Medicine in May, discovered that pulse oximetry overestimated oxygen levels in the blood by an average of 1.7% among Asian patients, 1.2% among Black patients, and 1.1% among Hispanic patients when compared to White patients.
This overestimation may have contributed to a patient's eligibility for certain Covid-19 therapies going unnoticed or being recognized late.
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