Skin color causes flaw in medical equipment, incorrect readings due to faulty design

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The Fatal Design Flaw of the Pulse Oximeter

In the first study to examine this issue among COVID-19 patients, researchers found that the inaccurate measurements resulted in a “systemic failure,” delaying care for many Black and Hispanic patients. The study adds a growing sense of urgency to an issue raised decades ago.

spectrum.ieee.org

If someone is seeking medical care, the color of their skin shouldn’t matter. But, according to new research, pulse oximeters’ performance and accuracy apparently hinges on it. Inaccurate blood-oxygen measurements, in other words, made by pulse oximeters have had clear consequences for people of color during the COVID-19 pandemic.

“That device ended up being essentially a gatekeeper for how we treat a lot of these patients,” said Dr. Tianshi David Wu, an assistant professor of medicine at Baylor College of Medicine, in Houston, and one of the authors of the study.

For decades, scientists have found that pulse oximeters, devices that estimate blood-oxygen saturation, can be affected by a person’s skin color. In 2021, the FDA issued a warning about this limitation of pulse oximeters. The agency says it plans to hold a meeting on pulse oximeters later this year. Because low oxygen saturation, called hypoxemia, is a common symptom of COVID-19, low blood-oxygen levels qualify patients to receive certain medications. In the first study to examine this issue among COVID-19 patients, published in JAMA Internal Medicinein May, researchers found that the inaccurate measurements resulted in a “systemic failure,” delaying care for many Black and Hispanic patients, and in some cases, preventing them from receiving proper medications. The study adds a growing sense of urgency to an issue raised decades ago.

Pulse oximeters work by passing light through part of the body, usually a finger. These devices infer a patient's blood-oxygen saturation (that is, the percentage of hemoglobin carrying oxygen) from the absorption of light by hemoglobin, the pigment in blood that carries oxygen. In theory, pulse oximeters shouldn’t be affected by anything other than the levels of oxygen in the blood. But research has shown otherwise.

“If you have melanin, which is the pigment that's responsible for skin color…that could potentially affect the transmittance of the light going through the skin,” said Govind Rao, a professor of engineering and director of the Center for Advanced Sensor Technology at the University of Maryland, Baltimore County, who was not involved in the study.