A Deadly ‘ Blind Spot ’
Scientists work to correct skin color bias in pulse oximeters . BY GABRIELLA LUI
During the height of the COVID-19 pandemic , the news that pulse oximeters were consistently overestimating the blood oxygen levels of Black patients — and thus delaying their care — made headlines .
But experts had known for decades that skin pigmentation and melanin can affect the device ’ s ability to accurately measure oxygen saturation , an indicator of pulmonary health . Inaccurate readings likely contributed to the disproportionate deaths of patients with darker skin during the pandemic .
Kimani Toussaint , PhD , the Thomas J . Watson , Sr ., Professor of Science at Brown , is leading an effort to improve this important screening tool so that patients and physicians can trust the reading .
“ The focus is always the same thing : trying to develop a more equitable device ,” says Toussaint , the senior associate dean for research and strategic initiatives in Brown ’ s School of Engineering .
The pulse oximeter exhibits biases for two main reasons . First , FDA guidelines for calibrating the devices require at least 15 percent of participants to identify as “ dark-skinned ”— but they don ’ t specify how skin tone should be measured , or define “ dark skin tone .” Second , melanin not only absorbs ambient light but also contributes to light scattering , complicating measurement .
“ The organelles produced by melanosomes in the epidermis vary in size , density , and distribution depending on skin tone ,” Toussaint says . “ This means that , in addition to absorption , melanin-induced scatter also affects the measurement .” Together , these factors can cause the pulse oximeter to
A pulse oximeter prototype built by the Toussaint lab .
overestimate oxygen levels in darker skin .
Toussaint ’ s lab is trying to exploit the polarization properties of light so that devices are less sensitive to the absorption and scattering phenomena at the top epidermal layers at the measurement site , thus emphasizing contributions from the deeper layers of the skin .
The prototype , roughly the size of a shoebox , is undergoing clinical trials at The Miriam Hospital . Toussaint ’ s team is also translating their design into a small-scale wearable that goes around the wrist . Graduate student Rutendo Jakachira says that as light travels through their device ’ s larger optical system , the power decreases .
“ By the time the light is incident on the finger , we have lost a lot of power . This adds another layer of complexity when dealing with patients with low perfusion ,” Jakachira says . Working on a smaller scale allows for a small footprint between the light source and detectors , resulting in a more prominent and accurate signal — but it ’ s more costly , as they are “ essentially building a whole new device as we iterate ,” she says .
Toussaint says the inaccurate pulse oximeter is only “ the tip of the iceberg ” of health disparities in device manufacturing .
“ It ’ s a blind spot that is indicative of not having sufficient diversity across the entire development of this type of technology ,” Toussaint says . “ Technology itself can have bias , irrespective of the original intent .”
Meet Danoff Labs
The new building will house innovative research . BY BRIAN E . CLARK
At seven stories tall and with 300,000 square feet of space , the William A . and Ami Kuan Danoff Life Sciences Laboratories will become the largest academic laboratory building in Rhode Island .
Located in Providence ’ s Jewelry District , the facility will bring together biomedical experimentalists , engineers , physicians , computer scientists , entrepreneurs , and other scholars under one roof to solve complex interconnected
health and medical challenges .
Powered by 100-percent renewable electricity with emergency backup for resiliency , the all-electric laboratory building will be a first for Brown and stand as one of the first “ net zero ” lab constructions in New England .
Construction began in fall 2024 ; the University is targeting a 2027 completion date for the building .
WINTER 2025 l HEALTH DISCOVERIES @ BROWN 7