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FDA: Limitations of pulse oximeters, risk of error in some cases

October 27, 2022

Based on the blood oxygen sensor technology and testing principle, some specific situations will affect the reading of blood oxygen saturation and cause errors. Instead of a medical oximeter, there may be more misreadings due to the uneven blood oxygen sensor technology and the unprofessional operation of the user. The U.S. Food and Drug Administration recently signed a safety notification to inform healthcare practitioners and the public that pulse oximetry is limited and inaccurate in certain circumstances.

 

The COVID-19 pandemic has led to increased use of pulse oximeters. A study published in the New England Journal of Medicine in late 2020 suggested that the device may be less accurate in people with hyperpigmented skin. Although in most cases these inaccurate measurements may be of little clinical significance, these inaccurate monitoring still carry the risk of missing hypoxia. The FDA notes that it is important to understand the limitations of pulse oximetry and how to calculate and interpret the accuracy.

 

This safety advisory includes several recommendations for healthcare practitioners, including being aware that a variety of factors can affect the accuracy of pulse oximetry readings, such as skin pigmentation, poor circulation, skin thickness, skin temperature, current use Tobacco and nail polish. Consult the device label or manufacturer's website for the accuracy of a specific brand of pulse oximeter and oximeter, as different brands and sensors may have different levels of accuracy. According to the notification, pulse oximeters are least accurate when blood oxygen saturation is below 80 percent.

 

Health care workers should consider factors affecting accuracy when using pulse oximeters for diagnostic and treatment decisions. The FDA safety communication states that pulse oximeter readings should be used as an estimate of oxygen saturation and, where possible, diagnostic and treatment decisions should be based on trends in pulse oximeter readings over time, rather than absolute thresholds . The FDA also noted that it only reviews medical pulse oximeters for accuracy, not non-medical oximeters for general health or exercise/aviation purposes.

 

The safety newsletter also provides advice for patients and caregivers who are monitoring their condition at home, including how to take readings, how to interpret them and when to contact a healthcare worker.

 

For the best pulse oximetry readings, the FDA recommends following the product manufacturer's instructions. When placing the pulse oximeter, make sure your hands are warm, relaxed, free of nail polish and that your fingers are below your heart. Also, keep your body still and especially don't move the pulse oximeter to ensure accurate readings. Record the oxygen level when the reading shows a steady number and the date and time of the reading to track changes in readings and tell your doctor.

 

When recording readings, patients and caregivers should be aware that we may need to contact our physicians when blood oxygen levels are lower than previous measurements or gradually decrease over time. Although some patients with low oxygen levels may have no symptoms, the FDA urges patients monitoring oxygen saturation at home to be aware of the following symptoms of low oxygen levels:

 

Unusual color of face, lips or nails.

 

shortness of breath, difficulty breathing, or a worsening cough;

 

restless and uncomfortable;

 

chest pain and fast heartbeat

 

The FDA notes that over-the-counter products that can be purchased in stores or online are not intended for medical purposes. According to the Safety Communications, the FDA is committed to continuing to evaluate the safety, efficacy and availability of medical devices, especially those in greater demand during the COVID-19 pandemic. Currently, the FDA is evaluating published literature on various factors that may affect pulse oximetry readings and performance, with a focus on literature that is less accurate due to skin pigmentation. Based on these new findings, the FDA may re-evaluate the pulse oximetry guidance document.