How reliable are pulse oximeter devices?

Pulse oximeter devices became popular during the COVID-19 pandemic because they allow people to monitor their own oxygen saturation (the concentration of oxygen in the blood). However, the values provided by these devices may not always be accurate. The FDA (US Food and Drug Administration) issued a warning about this in new guidance published on Friday.

What is a pulse oximeter device?

A pulse oximeter is a medical device that measures the proportion of oxygenated hemoglobin in the blood in pulsating vessels, particularly in the capillaries of a finger or ear.

Can there be errors in the values measured by pulse oximeter devices? 

The FDA says that various factors, such as skin health, skin thickness, current tobacco use, nail polish use, poor blood circulation and dark skin pigmentation, can affect the accuracy of pulse oximeter devices. A recent report in the New England Journal of Medicine shows that Black patients may not obtain accurate measurements from some pulse oximeter devices.

Dr William Maisel, Director of the FDA's Office of Product Evaluation and Quality, said in a statement, "Although pulse oximeter devices are useful for estimating blood oxygen levels, these devices have limitations that can cause inaccurate readings." he said.

Maisel encouraged people to pay attention to all health symptoms, particularly if they have signs indicating low oxygen saturation, such as shortness of breath or bluish discoloration of their face, lips or nails.

"Patients with conditions such as COVID-19 should not rely solely on devices such as pulse oximeters to monitor their health at home, because they do not replace a medical diagnosis provided by a healthcare professional." he said.

A pulse oximeter device, typically placed on a fingertip, uses infrared rays to calculate the amount of oxygen in the blood and the pulse rate. Typical oxygen saturation levels range from 95% to 100% and may be slightly lower in people with lung problems. Healthcare professionals and consumers have monitored their oxygen saturation throughout the pandemic because COVID-19 can cause oxygen saturation to fall; a drop below 95% requires attention, while a drop below 90% causes concern.

According to the FDA warning, consumers can buy unlicensed oximeters in stores or online, but these are not designed for medical use and are not subject to FDA review. Licensed oximeters undergo agency review and are generally used in hospitals and doctors' offices, although patients sometimes obtain licensed oximeters for home use.

However, the fact that no smartwatch or wristband has so far been approved for measuring oxygen saturation must also be remembered.

The FDA guidance provides tips to help patients and caregivers obtain an accurate reading and interpret the results correctly. According to the guidance, changes or trends in measurements are more meaningful than a single measurement. Patients should contact their healthcare professionals if they are concerned about pulse oximeter data, particularly if their symptoms worsen or they think they may have COVID-19.

The FDA is evaluating existing research on the accuracy of pulse oximeter devices, focusing particularly on studies assessing whether the devices are less accurate for people with dark skin. Based on new findings, the FDA may update its pulse oximeter guidance and will inform the public if new information emerges. The FDA also encourages consumers to report any pulse oximeter problems through the MedWatch Voluntary Reporting Form.