Skin color would affect pulse oximeter readings

NEW YORK (HPD) — Health authorities in the United States are scrutinizing devices that measure the level of oxygen in the blood using light, as recent studies indicate that they are not as effective in people of color as in whites.

Pulse oximeters are usually attached to a finger and are in common use in hospitals around the world. Home-use versions were hot sellers during the coronavirus pandemic.

But recent studies indicate that skin pigmentation can affect measurements. In 2021, the Food and Drug Administration (FDA) warned of possible inaccuracies when a study found that artifacts tended to overestimate oxygen levels in black patients.

“The fact that such a widely used device could have any such discrepancies surprised me deeply,” said Michael Sjoding, a pulmonologist at the University of Michigan who led the study. “I make a lot of medical decisions based on this device.

The FDA convened a panel of experts Tuesday to discuss “growing concerns” about the devices, recommendations to patients and doctors and how to assess their accuracy.

Oxygen levels can be measured by drawing blood from an artery in the wrist. This method is still the most accurate, but it’s a bit more difficult and painful, so it’s not used as often, said Leo Celi, a physician and pulse oximetry researcher.

By comparison, the pulse oximeter is faster, easier to use, and less invasive.

When strapped onto a finger, the pulse oximeter sends two light waves through the skin, explained Rutendo Jakachira, a graduate student at Brown University who studies pulse oximetry. By measuring light absorption, the device calculates how much oxygen is flowing through the blood.

The problem is that melanin, a natural pigment that gives skin its color, also absorbs light, Jakachira said. And if the artifact is not made with the melanin factor in mind, the additional absorption can throw off the measurement.

There is increasing evidence that this factor affects pulse oximeters currently on the market.

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