FDA: Pulse oximeters have limitations, risk for inaccuracy under certain circumstances

The FDA has issued a safety communication to inform health care providers and the public that pulse oximeters have limitations and a risk for inaccuracy under certain circumstances.

The COVID-19 pandemic has caused an increase in the use of pulse oximeters. A recent study published in The New England Journal of Medicine suggested that the devices may be less accurate in people with dark skin pigmentation. (See Healio’s coverage of this study here.) The level of these inaccuracies may not be clinically meaningful in many cases, but there is still a risk for inaccurate measurements that may result in undetected low oxygen saturation levels. The FDA said it is important to understand the limitations of pulse oximetry and how accuracy is calculated and interpretated.

The safety communication includes several recommendations for health care providers, including awareness that multiple factors can affect the accuracy of a pulse oximeter reading, such as skin pigmentation, poor circulation, skin thickness, skin temperature, current tobacco use and fingernail polish. Refer to the device labeling or the manufacturer website to understand the accuracy of a particular brand of pulse oximeter and sensor, as different brands and sensors may have a different accuracy level. Pulse oximeters are least accurate when oxygen saturations are less than 80%, according to the safety communication.

Health care providers should consider accuracy limitations when using the pulse oximeter to assist in diagnosis and treatment decisions. The FDA safety communication notes that pulse oximeter readings should be used as an estimate of blood oxygen saturation, and diagnosis and treatment decisions should be based on trends in pulse oximeter readings over time rather than absolute thresholds, when possible. The FDA also notes that it only reviews the accuracy of prescription-use pulse oximeters, not over-the-counter oximeters for general wellness or sporting/aviation purposes.

The safety communication also provides recommendations for patients and caregivers who monitor their condition at home, including how to take a reading, how to interpret a reading and when to contact a health care provider.

For the best pulse oximetry readings, the FDA recommends following specific manufacturer instructions; assure that the hand is warm, relaxed, free of nail polish and held below the heart when placing the pulse oximeter; sit still and do not move the part of the body where the pulse oximeter is located; wait until the reading displays one steady, unchanging number; and write down oxygen levels with the date and time of reading to easily track changes and report these to a health care provider.

When recording a reading, patients and caregivers should be aware whether the oxygen level is lower than previous measurements or gradually decreasing over time as these changes may warrant contacting a health care provider. While some patients with low oxygen levels may not show signs, the FDA urges patients who monitor oxygen levels at home to be aware of the following signs and symptoms of low oxygen levels:

• bluish coloring in the face, lips or nails;
• shortness of breath, difficulty breathing or worsening cough;
• restlessness;
• discomfort;
• chest pain and/or tightness; and
• increasing heart rate

The FDA notes that over-the-counter products that can be bought at the store or online are not intended for medical purposes.

According to the safety communication, the FDA is committed to continuing the evaluation of the safety, effectiveness and availability of medical devices, especially those in higher demand during the COVID-19 pandemic. Currently, the FDA is evaluating published literature regarding factors that may affect pulse oximetry readings and performance, focusing on literature deeming less accuracy among individuals with darker skin pigmentation.

Based on these new findings, the FDA may reassess the pulse oximetry guidance document.