San Francisco,  As smartwatches now claim to read blood oxygen levels, the US Food and Drug Administration (FDA) has raised fresh concerns over pulse oximeters that monitor blood oxygen levels in the hospital and at home.

According to an FDA advisory panel, blood oxygen monitors need to be more carefully regulated as they don't work as well on people with darker skin tones.

In 2021 during the pandemic, the FDA had issued an alert saying that these devices have "limitations".

"As part of its premarket evaluation of pulse oximeters, FDA has long required premarket data assessing pulse oximeter performance in subjects with different skin pigmentation. However, a December 2020 published report suggests that pulse oximeters may be less accurate in patients with darker skin pigmentation," said the FDA panel in its report.

The panel reviewed multiple research studies that show oximeters don't work as well on darker skin.

It delayed Covid treatments in Black patients because the devices didn't show dropping oxygen levels, according to one study.

The over-the-counter pulse oximeters or "wellness" devices aren't reviewed by the FDA.

An assessment of the US pulse oximeter market demonstrates the use of these devices increased during the first year of the Covid-19 pandemic.

Since the December 2020 study, additional real-world studies have been published suggesting increased risk for missed diagnosis of "occult hypoxemia", delays in treatment eligibility decisions and worse patient outcomes among subjects with darker skin pigmentation.

"Occult hypoxemia" is defined as Sao2 less than 88 per cent despite a Spo2 of greater than 92 per cent, based on previously published parameters.

Pulse oximeters are widely used by many types of healthcare providers and consumers to obtain an indirect measure (SpO2) of arterial blood oxygen saturation (SaO2).

"We need to take appropriate steps to remove the growing uncertainty around these devices and ensure the health and safety of the public," anesthesiologist Jesse Ehrenfeld told the panel, reports The Verge.