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Making Monitors That Work for All Races

Female patient monitored using Lifebox pulse oximeter [essential oxygen monitor]. Taken January 19, 2013
Female patient monitored using Lifebox pulse oximeter [essential oxygen monitor]. Taken January 19, 2013

Doctors have long known that pulse oximeters are less accurate in estimating blood oxygen levels in non-white patients, but the discrepancies were considered insignificant. The COVID-19 pandemic exposed some of the real dangers of these flaws, as the devices gave falsely high oxygen readings in patients with dark skin.

Medical device makers and scientists are working on new technologies to improve widely-used devices that assess potential heart and respiratory problems given mounting evidence that current ones could lead to inadequate healthcare for patients with darker skin.

The devices, which clip to a fingertip, pass red and infrared light through the skin and measure how much light is absorbed by oxygen-carrying hemoglobin. Melanin pigment in darker skin also absorbs the light, however, and current devices do not adjust for that effect.

In recent years, studies have shown that low oxygen levels more often go undetected in Black adults and infants, and that Black patients receive less supplemental oxygen than similarly ill White patients due to pulse oximeter inaccuracies.

To address the problem, some researchers are testing devices that use other wavelengths of light not absorbed by melanin.

Among the furthest along in development is a sensor from Rockley Photonics Holdings that uses spectrophotometers and laser instruments on chips to emit a broad spectrum of light, which the company says more accurately monitors not only blood oxygen but also hydration, blood pressure and other biomarkers.

At Brown University in the United States, researchers Kimani Toussaint and Rutendo Jakachira are experimenting with light at wavelengths insensitive to melanin.

Valencia Koomson of Tufts University is developing a device that takes into account a patient's skin tone and presence of melanin to better adjust oxygen level estimates.

All agree that more accurate pulse oximeters are long overdue.

COVID amplified those risks. The coronavirus can cause dangerously low oxygen levels even before a patient feels out of breath or appears to be in distress, making healthcare providers even more dependent on accurate oximeter readings.

Pulse oximeter problems "suddenly became enormous" during the pandemic, said Dr. Philip Bickler, director of the University of California, San Francisco's (UCSF) Hypoxia Research & Pulse Oximeter Test Facility.

Bickler, whose laboratory analyzes pulse oximeter accuracy for manufacturers, said he believes industry leaders "are all working to address the devices' shortcomings."

Experts say the FDA needs to strengthen its criteria for approving new devices. Current rules require that pulse oximeters be tested in a minimum of just 10 subjects, only two of whom must be "darkly-pigmented."

The agency does not require a standardized assessment for classifying skin pigmentation, tools that would be critical in evaluating inaccuracies.

The first step to ensure appropriate access to care requires raising awareness about the potential inaccuracies, especially among healthcare providers, she said.

While the devices are still useful, UCSF's Bickler said, doctors "should not base patient care only on pulse oximeter findings."