Multiple studies have shown that people with darker skin pigmentation run a higher risk of being misdiagnosed and undertreated than patients with lighter skin due to inaccurate oxygen level readings
Though pulse oximeters are not a standard clinical laboratory device, clinical laboratory scientists (aka, medical technologists) know of them and understand their function, particularly with hospital patients.
Now, scientists at multiple institutions are working to improve the basic pulse oximeter’s design by making it capable of measuring multiple biomarkers, as well as addressing long-standing inaccuracies in the device when used on people with darker skin pigmentation.
This ongoing research demonstrates how new technologies are enabling innovators to add useful functions to standard, well-accepted devices.
Valencia Koomson, PhD (above), Associate Professor, Electrical and Computer Engineering, and head of the Advanced Integrated Circuits and Systems Lab at Tufts University, has developed a pulse oximeter that measures oxygenation in tissue, rather than in blood. Her approach could ensure patients with darker skin pigmentation will be accurately diagnosed at the point-of-care. Though generally not used in clinical laboratory settings, medical technologists will be interested to learn of these new innovations in pulse oximeters. (Photo copyright: Tufts University.)
Measuring Tissues Instead of Blood
The pulse oximeter—a device that attaches to a person’s finger—uses red and infrared light to measure blood oxygen saturation (SpO2) and display pulse rate.
Studies in 2022 that looked into how hospitals administered oxygen to different patients found that inconsistent pulse oximeter readings could cause caregivers to administer less oxygen than is actually needed to people with darker skin pigmentation.
This is because melanin in the skin can interfere with “absorption of light used to measure oxygenated blood in a person’s finger,” according to a National Science Foundation (NSF) news story. Such inaccurate pulse oximeter readings can lead to “inaccurate readings and poorer treatment outcomes” for people with dark skin tones, the NSF wrote.
“Addressing this problem will require innovation in pulse oximeter design and revised regulatory standards,” said Valencia Koomson, PhD, Associate Professor, Electrical and Computer Engineering, Tufts University, Medford, Massachusetts, in the NSF news story.
Koomson, who leads the Advance Integrated Circuit and Systems Lab at Tufts, has developed a prototype pulse oximeter device, which NSF explained, measures oxygenation in biological tissues instead of blood.
NSF supports her pulse oximeter research through the National Science Foundation Partnerships for Innovation (PFI) program.
“My lab’s work on pulse oximeter devices will provide an alternative technology to address many confounding factors that affect pulse oximeter accuracy, including skin pigmentation, motion artifact, and others,” Koomson said.
National Public Radio (NPR) said Koomson’s device has built-in “technology that can measure a person’s skin tone.”
“We can send more light if there’s a higher level of melanin present, so that melanin doesn’t become a confounding factor that obscures our results,” Koomson told NPR.
Another Pulse Oximeter Redesign
Another new approach to pulse oximetry was developed at Brown University in Providence, Rhode Island.
Rutendo Jakachira, Research Assistant, School of Engineering, and a PhD student in physics, turned to new optical techniques to address the challenge of oxygen saturation levels in dark skin tones, according to a Brown University news release.
Jakachira and Kimani Toussaint, PhD, Professor of Engineering and Senior Associate Dean in the School of Engineering, say they have created possibly the first LED-based light source to emit radially polarized light.
When the LED passes light through a person’s finger, the device calculates the amount of light the hemoglobin in the blood absorbed, NPR explained.
“We did a preliminary study on about five people, and although it was a small study, the results are promising,” said Jakachira, who plans a larger study and clinical trial.
Study Suggests Patients with Darker Skin May Have Received Delayed COVID-19 Care
Meanwhile, a study published in the American Journal of Epidemiology (AJE) suggested pulse oximeter errors may have led to a 4.5-hour delay in COVID-19 treatment of patients with darker skin pigmentation, according to a news release from the University of California San Francisco.
The researchers analyzed electronic health record (EHR) data from 43,753 patients at Sutter Health in Sacramento, California, who had SpO2 measurements done between January 2020 and February 2022, and 8,735 patients seen for COVID-19 between July 2020 and February 2021 in the hospital’s emergency department.
In their AJE paper, they wrote, “We investigated whether or not pulse oximetry systematically underestimated oxygen saturation in patients who identified as NHB [non-Hispanic Black/African-American] as compared with NHW [non-Hispanic White] counterparts. We also assessed whether or not differences in oxygen saturation measurement affected hospital admission, care delivered, or return to the hospital post discharge among patients with COVID-19.
“We found evidence of differential pulse oximeter measurement error in NHB individuals, resulting in nonrandom overestimation of blood oxygenation as compared with NHW individuals. NHB individuals were also more likely to have hypoxemia [abnormally low oxygen levels in the blood] not detected by pulse oximetry.
“For NHB patients presenting in the ED with COVID-19, we found that overestimation of oxygen saturation was associated with underestimation of the need for admission and underestimation of the need for treatment with dexamethasone and supplemental oxygen. Additionally, we observed associated delays in dexamethasone initiation and initiation of oxygen supplementation.
“There are also broader implications beyond COVID-19, as differential pulse oximeter accuracy has the potential to exacerbate disparities for any condition that relies upon blood oxygenation measurement to inform clinical decision-making.”
Importance of Accurate Readings
Developing pulse oximeters that are accurate for all people, regardless of skin tone, is clearly an important breakthrough. Medical laboratory leaders and pathologists recognize that SpO2 data—along with clinical laboratory test results—are critical for successful diagnostics and treatment. Thus, new technologies that add useful functions to well-accepted devices are positive developments and worth watching.
—Donna Marie Pocius
Related Information:
Researcher Addresses Longstanding Problem with Pulse Oximeters and Dark-skinned Patients
When it Comes to Darker Skin, Pulse Oximeters Fall Short
Brown PhD Student Working to Correct Skin Color Bias in Pulse Oximeters
Pulse Oximeters Don’t Work as Well on Darker Skin, Leading to Flawed COVID-19 Care