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Oximeter blood oxygen devices don't work as well on black people!

Brucilla

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I was today years old when I learned that oximeters have up to a 12% error rate on black people, especially if we are dark skinned.

I bought one way back in March, and whenever my asthma acted up I would use it to make sure I was good.

Welp, it turns out the pigment in our skin screws up the results sometimes and people are dying over it because the doctors don't know that the oxygen levels are too low.

The same is true for fitness measurement devices. :-/

So if you are hospitalized and aren't breathing right and the oximeter says you're fine, insist on getting a blood test to check your oxygen levels!

Here's the article: (tldr; our skin pigment messes with the light beam that measures the oxygen levels... they are calibrated for white skin)

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Pulse Oximeter Devices Have Higher Error Rate in Black Patients

Pulse oximeters are one of the most commonly used tools in medicine. The small devices, which resemble a clothespin, measure blood oxygen when clipped onto a fingertip, and they can quickly indicate whether a patient needs urgent medical care.

Health providers use them when they take vital signs and when they evaluate patients for treatment. Ever since the pandemic started, doctors have encouraged patients with Covid to use them at home.

But in Black patients, the devices can provide misleading results in more than one in 10 people, according to a new study.

The findings, which were published last week as a letter to the editor of a top medical journal, sent ripples of dismay through the medical community, which relies heavily on the devices to decide whether to admit patients or send them home.


The report also stirred concerns because the pandemic is taking a disproportionate toll on Black and Hispanic Americans, drawing attention to racial health disparities and prompting soul-searching among doctors about bias that permeates the practice of medicine. There have been several reports of acutely ill Black patients who sought medical care, only to be turned away, and studies have found that African-Americans were hospitalized at higher rates, suggesting delays in access to medical care.

The researchers who conducted the oximeter study said they were surprised by the findings. Though scientific reports of the inaccuracies have been published in the past, they did not receive widespread attention or get incorporated into medical training.

“I think most of the medical community has been operating on the assumption that pulse oximetry is quite accurate,” said Dr. Michael W. Sjoding, an assistant professor of internal medicine at the University of Michigan Medical School and lead author of the new report, which appeared in the New England Journal of Medicine. “I’m a trained pulmonologist and critical care physician, and I had no understanding that the pulse ox was potentially inaccurate — and that I was missing hypoxemia in a certain minority of patients.”

Dr. Utibe Essien, an assistant professor of medicine at the University of Pittsburgh School of Medicine who studies racial disparities in cardiovascular disease, noted that doctors practicing telemedicine have relied on reporting from these devices.



“If we cannot ensure that its definition of low oxygen in people, especially Black people, is accurate, there is a concern that it is increasing or driving disparities,” he said.


Pulse oximeters work by shining two wavelengths of light, a red light and an infrared light, that pass through the skin of a finger.

The device detects the color of blood, which differs depending on the amount of oxygen. Oxygenated blood is bright cherry red, and deoxygenated blood has a more purplish hue. Depending on the hue, different amounts of light from the device are absorbed, and the oximeter analyzes the proportions of the absorption and calculates the amount of oxygen. Researchers suspect that the inaccurate readings may be occurring because of the way the light is absorbed by darker skin pigments.

Dr. Philip Bickler, the director of the hypoxia research laboratory at University of California, San Francisco, which tests the performance of pulse oximeters, said the simplest way to explain the inaccuracies in patients with darker skin is that the pigment “scatters the light around, so the signal is reduced. It’s like adding static to your radio signal. You get more noise, less signal.” (Dark nail polish also reduces the accuracy, as do cold fingers.)

Generally health providers treating patients take many metrics into account, including imaging scans, inflammatory markers and other clinical signs, said Dr. Darshali Vyas, a resident physician at Massachusetts General Hospital who has done research on medical decision-making tools that incorporate race. But, she said, “pulse oximetry remains one of the mainstays.”

The new findings “help quantify the potential harm done by a ubiquitous medical tool that may normalize white skin as the default,” Dr. Vyas said in an email. She added that this could be “especially concerning” for doctors using the readings to adjust the amount of supplemental oxygen they give Covid patients, and to determine transfers to intensive care.

The study compared pulse oximeter measures with values obtained from a more invasive type of test, called an arterial blood gas test, carried out in the same patients at about the same time. Arterial blood gas tests are used more rarely, because they require drawing blood from an artery, which is a more invasive procedure than drawing blood from a vein.



Oxygen levels below 95 percent are considered abnormal, so “a small difference in pulse oximetry value in this range of 92 to 96 percent could be the difference in deciding whether the patient is really sick or not really sick, or needs different treatment or not,” Dr. Sjoding said.

Another analysis in the study examined a multi-hospital database to compare 37,308 similar paired test results from intensive care patients who had been hospitalized at 178 medical centers in 2014 and 2015. That analysis, which was not adjusted, found similar discrepancies.

Dr. Sjoding said he and his colleagues embarked on the study after hospitals in Ann Arbor, Mich., which typically care for a predominantly white patient population, received a large influx of critically ill Covid patients from Detroit many of whom were African-American. “We started seeing some discrepancies with arterial blood gas, and we didn’t know what to make of it,” he said.

He recalled reading an article published in The Boston Review in August about racial disparities in the accuracy of pulse oximeter readings. The writer of that article, Amy Moran-Thomas, an anthropologist at M.I.T., became interested in the device after buying one when her husband was sick with Covid. She dug up scientific papers published as far back as 2005 and 2007 that reported inaccuracies in pulse oximeter readings in dark-skinned individuals at low oxygen saturation levels.

Dr. Sjoding and his colleagues decided to do a study using data that had already been collected during routine inpatient care at the hospital. “What we were seeing anecdotally was exactly what we ended up showing in the final paper, that on the monitor in the patient’s room, the pulse oximeter would be reading ‘normal,’ but when we got an arterial blood gas, the saturation on the gas was low,” he said.

that reported on inaccuracies in people with darkly pigmented skin. He said oximetry errors have been known from lab studies for quite some time, but the new paper provides real world evidence.

“It’s apparent that there are racial differences in how oximeters perform — we pointed that out way back 15 years ago,” he said. “The biggest issue is why it hasn’t been fixed. Now the Covid pandemic has brought this all to the fore: All of a sudden the medical system is overwhelmed with patients with low oxygen.”

Dr. Bickler’s article in 2005 suggested the devices could be improved with a setting that adjusts to a different calibration for a darker pigmented skin. “I’m not sure it’s easy to do, but there should be a way of fixing this,” he said. The paper also suggested the devices carry warning labels about the potential for overestimating oxygen levels in dark-skinned patients.

Findings of similar disparities have also been reported in physical fitness devices.

Dr. Sjoding and his colleagues aren’t advising the oximeters be discarded. The vast majority of readings are accurate, he said. “The pulse ox is an amazing tool, but we treat it like it’s way more accurate than it actually is,” he said. Dr. Steven Gay, an associate professor of medicine at University of Michigan who is one of the report’s other authors, said the study is a reminder to look at patients holistically and individually.

“To take the best care of our patients, we have to know these things, so we don’t make assumptions that a patient is doing well, just because the data isn’t what it’s supposed to be,” he said. “It reminds us that as much as we speak about medicine as a science, there is an art to it.”
 
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SnipYoFlap

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we need one of our young black scientists or inventors to improve this device, or invent a new one for melanated skin, so that we can get an accurate reading.
 

Santigold

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Oxygen levels below 95 percent are considered abnormal, so “a small difference in pulse oximetry value in this range of 92 to 96 percent could be the difference in deciding whether the patient is really sick or not really sick, or needs different treatment or not,” Dr. Sjoding said.

I used an oximeter twice today (went to the emergency room for pains I've been having) and my results came back at 92%. I didn't know that was abnormal....:(

I wonder if the fact I was struggling to stay calm since I hate visiting hospitals had an impact on my results?
 

Brucilla

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I used an oximeter twice today (went to the emergency room for pains I've been having) and my results came back at 92%. I didn't know that was abnormal....:(

I wonder if the fact I was struggling to stay calm since I hate visiting hospitals had an impact on my results?

I doubt it! 92% is VERY low! I think they're supposed to give you oxygen if you're below 94%. Were your hands cold?
 

cdelacreme

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Why not place it on the ear lobe? Looks like they aren't adjusting treatment for pigmented people. Pulse ox on earlobe is much more accurate than fingers
 

Brucilla

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Why not place it on the ear lobe? Looks like they aren't adjusting treatment for pigmented people. Pulse ox on earlobe is much more accurate than fingers

I'm thinking it would be the same problem. The issue is our pigment scattering the light beam, not the extremity that it's on unfortunately.
 

SouthernNotCountry

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Wow, thanks for posting this. When just about everything is made for only yts in mind, I guess I shouldn't be surprised that even medical devices work against us. I'm sure black families that have lost people to Covid after being sent home are going to be interested in this study.
 

Kira Kira

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I think that the article is actually stating the opposite, that pulse oximeters have a harder time reading oxygen levels in darker skinned individuals, and might give falsely lower readings (same with people wearing dark nail polish).

Pulse oximeters work by shining two wavelengths of light, a red light and an infrared light, that pass through the skin of a finger.

The best way to gage oxygen levels would be through an ABG (arterial blood has), where they draw blood arterially, and get a reading through measuring blood oxygen levels. Too much oxygen (or receiving oxygen when not needed) can be just as harmful to the body, as not receiving enough oxygen.
 

Brucilla

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I think that the article is actually stating the opposite, that pulse oximeters have a harder time reading oxygen levels in darker skinned individuals, and might give falsely lower readings (same with people wearing dark nail polish).



The best way to gage oxygen levels would be through an ABG (arterial blood has), where they draw blood arterially, and get a reading through measuring blood oxygen levels. Too much oxygen (or receiving oxygen when not needed) can be just as harmful to the body, as not receiving enough oxygen.


Interesting... I wish the article was more specific but this is what stood out to me:

"Dr. Sjoding and his colleagues decided to do a study using data that had already been collected during routine inpatient care at the hospital. “What we were seeing anecdotally was exactly what we ended up showing in the final paper, that on the monitor in the patient’s room, the pulse oximeter would be reading ‘normal,’ but when we got an arterial blood gas, the saturation on the gas was low,” he said."
 

Rickysrose

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Hmm wonder how "arterial blood gas" is obtained and if it's something easily asked for
 

Nikki_04

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This only applies to those who have pigmented nail beds. There are some black people who have a brownish tint to their nail beds. The oximeter looks at the color of the tissue under your nails, anything that obscures its view (i.e. nail polish) will affect the accuracy.
 

Nikki_04

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Hmm wonder how "arterial blood gas" is obtained and if it's something easily asked for

They need arterial blood, so they would have to take blood from an arterial line, which is not typically something you ask for and is usually reserved for sick patients in the ICU or patients having a high-risk surgery.

Depending on what you are looking for they can draw blood gases (not arterial blood gases) from a vein, which is something that can be done by going to the lab.
 

Stealyourman

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Pulse oximeters measure oxygen in the capillary bed,not in the blood specifically like ABG's do.

Also,a low reading is considered less than 90%,not 95
 

Bottom Btch

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Pulse oximeters measure oxygen in the capillary bed,not in the blood specifically like ABG's do.

Also,a low reading is considered less than 90%,not 95

Came to say this. Optimal oxygenation is between 95-100% however, 90 or more is acceptable in the hospital. That being said, you can check oxygenation by doing the capillary refills on the nail beds in both the hands and feet. Also, for darker skinned people, look at the lips, gums for a bluish tinge, if your SPO2 is saying 98% but you see that it is blue (cyanotic) then yes, you have poor oxygenation. ABGs aren't routine and are usually used for patients who have some kind of respiratory disorder or who have some other systemic issue that's causing low oxygenation, i.e neuro or cardio diseases.
 

Cinnahs

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I had no idea this was an issue. I can use my pulse oximeter fairly easily but my complexion isn't super deep.
 

Brucilla

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They need arterial blood, so they would have to take blood from an arterial line, which is not typically something you ask for and is usually reserved for sick patients in the ICU or patients having a high-risk surgery.

Depending on what you are looking for they can draw blood gases (not arterial blood gases) from a vein, which is something that can be done by going to the lab.

So if our nail beds are peach we're good? I wish the article was more specific about this.
 

cdelacreme

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A person's adequate oxygenation can be low and is their normal baseline especially if they have disease processes like COPD so excessive oxygenation can actually prove deleterious for them.
 

Tom Foolery

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Scientists are searching for solutions after studies show pulse oximeters don't work as well for people of color​

A medical worker examines a female patient with an oximeter device during the coronavirus outbreak.

A medical worker examines a female patient with an oximeter device during the coronavirus outbreak.
(CNN) — Often when Dr. Thomas Valley sees a new patient in the intensive care unit at Michigan Medicine in Ann Arbor, he clamps a pulse oximeter on their finger -- one of the 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.
But recently, Valley, an assistant professor in the University of Michigan's Division of Pulmonary and Critical Care, realized first-hand that the small devicemay yield less accurate oxygen readings in patients with dark skin.
This device is crucial in the fight against Covid. It may not work on dark skin
One end of the device sends light through the finger while a 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 purplish blood is less. If the device isn't calibrated for darker skin tones, the pigmentation of the skin could affect how the light is absorbed by the sensor, leading to flawed oxygen readings.
On a person of color, the pulse oximeter could indicate a patient's oxygen levels are normal, suggesting they could be discharged home -- but then their blood samples might show low oxygen levels, suggesting they not only needed 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."

Study confirms pandemic hit Black Americans, Native Americans and Latinos harder than Whites
Before the pandemic, the majority of Valley's patients at Michigan Medicine were White. But as the hospital treated more Covid-19 patients, Valley realized that many were Black or brown patients coming from other overburdened facilities.
Since then, Valley and his colleagues have collected data on how often pulse oximeters overestimate oxygen levels among their Black and brown patients. Their findings suggest that Black patients have nearly three times the frequency as White patients of experiencing blood oxygen levels less than 88% despite showing 92% to 96% on a pulse oximetry device. A normal level of oxygen is usually around 95% or higher.
"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's and his colleagues' experiences add to a growing body of research -- dating back to the 1980s -- that suggests flawed pulse oximeter readings among Black and brown patients can be a real and life-threatening issue in medical care.
The latest study on flawed pulse oximeter readings, published Monday in the journal JAMA Internal Medicine and which Valley was not involved in, found that among more than 3,000 hospitalized patients receiving intensive care, Asian, Black and Hispanic patients received less supplemental oxygen than White patients, and that was associated with differences in their pulse oximeter readings.
Research published by Valley and his colleagues last week in the medical journal BMJ found that Black patients had higher odds than White patients of having low blood oxygen noted in their blood-drawn readings but not detected by pulse oximetry. That finding was based on data from the Veterans Health Administration where pulse oximeter readings were paired with oxygen level measurements from drawing blood.
A separate study of about 7,000 Covid-19 patients, previously published in May in the journal JAMA Internal Medicine, found that compared with White patients, 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. That overestimation may have contributed to an unrecognized or delayed recognition of a patient's eligibility to receive certain Covid-19 therapies.

'The consequences of the neglect ... has been revealed'​


But only just recently the public has been made more aware of this health disparity, and US health officials have announced plans to investigate the accuracy of pulse oximeters.
"It's problematic," Valley said.
"There was a study just like ours done in 1990, but at a smaller scale at a single center. The problem from 1990 to 2020 is really a problem in dissemination and education. In medical school, in residency, in fellowship, I didn't know about this problem," he said. "It's not that we're now using pulse oximeters more often. I use a pulse oximeter every day, multiple times a day, all day in the intensive care unit, and that's unchanged from 10 years ago. It's almost like my right hand in an intensive care unit. We depend on what someone's oxygen levels are."
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 monitored with pulse oximetry, was declared a public health emergency of international concern.
People are buying pulse oximeters to try and detect coronavirus at home. Do you need one?
Some experts view the pandemic as shedding more of a spotlight on the pulse oximeter's limitations in measuring oxygen levels among Black and brown patients.

"I think that the Covid-19 pandemic has exacerbated this issue," said Rutendo Jakachira, a Ph.D. student in Brown University's Department of Physics, who is studying racial disparities in pulse oximetry.
"People have known that there's an issue with the over-estimation of these oxygen saturation levels, particularly in dark-skinned patients, but they did not appreciate the significance of this issue until the Covid-19 pandemic," she said. "The pandemic has seen an increased use of pulse oximeters in the hospital and in the home setting and thus the consequences of the neglect of the issues with errors in these pulse oximeter has been revealed."
Jakachira and her research adviser Kimani Toussaint argue that in the years following Aoyagi's invention, not enough clinical testing was done to improve the device to ensure equity across all demographics and skin tones.
"So, one thing that should be done immediately is improved calibration testing," Jakachira said, adding that currently, guidelines from the US Food and Drug Administration recommend such testing on pulse oximeters include at least 10 healthy subjects that vary in age and gender with a range of skin pigmentations, of which two individuals or 15% of the group -- "whichever is larger," the FDA guidance indicates -- have dark skin.
"This is probably not sufficient and not to draw statistical conclusions on disparities," she said. "So, using a more diverse population, calibration would be a great first step."

Future of pulse oximetry​


In April, the FDA issued new draft guidance that recommends companies making medical products should develop and submit a "race and ethnicity diversity plan" to the agency early in their development of products, and that plan should include enrolling diverse groups of people into their clinical trials.
It's been a year since CDC declared racism a public health threat. Now what?
Jakachira, Toussaint and their colleagues are developing non-invasive methods to make pulse oximeters more accurate in their blood oxygen readings for people with dark skin tones.
"What we're working on, we're trying to mitigate the skin tone issues by doing something interesting with the light, but it's a significant challenge and this really highlights the need to have diversity and inclusion," said Toussaint, a professor and senior associate dean in the School of Engineering at Brown University.
When pulse oximeters send beams of light through the fingertips to gauge blood oxygen levels, they are measuring how much oxygen has been absorbed by a certain molecule in the blood called hemoglobin. It turns out that both melanin and hemoglobin absorb light at similar wavelengths and separating out their relative contributions is what can be challenging. Melanin is the substance that produces pigmentation in our skin, hair and eyes.
"So, the melanin will overlap with the absorption properties of the hemoglobin in your blood," Toussaint said, which can lead to the pulse oximeter's flawed blood oxygen readings, as different people have different amounts of melanin.
The approach that Jakachira and Toussaint are taking in their quest for a solution is to try to cancel out the effect that absorbed melanin can have on how pulse oximeters measure blood oxygen levels.
"That's something that we think would be certainly a contribution but maybe translatable to other similar-based technologies that are not just pulse oximeters," Toussaint said, adding that he could not share additional details of this work as the research team is currently completing a patent application.

FDA advisers to discuss pulse oximeter accuracy​


The US Food and Drug Administration plans to convene a meeting of its medical devices advisers later this year to evaluate how pulse oximeters may yield inaccurate oxygen readings among people of color.
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A patient's oxygen levels are sometimes called the "fifth vital sign," and there is growing distress around how such investigations into how pulse oximeter inaccuracies among people of color did not occur sooner, according to an editorial that published Monday in the journal JAMA Internal Medicine.
"While the technical limitations of the pulse oximeter have been recognized for more than 30 years, investigations into clinical implications of hidden hypoxemia in patients with darker skin have been relatively (and distressingly) recent," Dr. Eric Ward of the University of California, San Francisco, and Dr. Mitchell Katz of NYC Health + Hospitals, wrote in their editorial.
They described one plan of action for change.
"Devices exist that perform more equitably but have never been widely distributed," Ward and Katz wrote. "Health care systems, including academic centers, are large-scale purchasers of pulse oximeters. If they make a commitment to buy only devices that function across skin tones, manufacturers would respond."
 

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