As a result of the coronavirus disease 2019 (COVID-19) public health emergency, pulse oximeter usage has increased in both hospital and home settings. The US Food and Drug Administration (FDA) describes a pulse oximeter as a device that is typically placed on a fingertip and uses light beams to provide an estimate of the oxygen saturation of the blood (SpO₂) and the pulse rate. These non-invasive devices are widely used to obtain an indirect measure of arterial blood oxygen saturation (SaO₂), the gold standard for evaluating blood oxygen saturation levels.  

Pulse oximetry is built on two physical principles: 1) arterial blood creates a pulsatile signal and 2) oxygenated haemoglobin (HbO₂) and reduced haemoglobin (HHb) have different absorption spectra.¹ Pulse oximeters typically emit light in the red and infrared wavelength regions (660 nm and 940 nm, respectively). More infrared light is absorbed by HbO₂, allowing red light to pass through, while HHb absorbs more red light and permits infrared light to pass through. The ratio of the red-light measurement to the infrared light measurement is calculated for the systolic and diastolic phases. Afterward, the ratio of these ratios is calculated and converted to SpO₂.²   

The FDA published the guidance for industry Pulse Oximeters – Premarket Notification Submissions [510(k)s] in March 2013 to assist sponsors in preparing 510(k) submissions for pulse oximeters.³ It covers class II devices regulated under 21 Code of Regulations (CFR) 870.2700 for oximeters and 21 CFR 870.2710 for ear oximeters. Of note, these devices are categorised as prescription-use pulse oximeters that undergo clinical testing and FDA review The FDA published the guidance for industry Pulse Oximeters – Premarket Notification Submissions [510(k)s] in March 2013 to assist sponsors in preparing 510(k) submissions for pulse oximeters.³ It covers class II devices regulated under 21 Code of Regulations (CFR) 870.2700 for oximeters and 21 CFR 870.2710 for ear oximeters. Of note, these devices are categorised as prescription-use pulse oximeters that undergo clinical testing and FDA review before being granted 510(k) clearance. The guidance includes recommendations on topics such as how to evaluate the accuracy of pulse oximeters and what to include in labelling.   

Limitations of Pulse Oximetry  

In December 2020, results were published in the New England Journal of Medicine about the potential for racial bias in pulse oximetry measurement.⁴ The findings described in the article suggested that pulse oximeter readings may not be as accurate in people with darker skin pigmentation. Relying on pulse oximetry to adjust supplemental oxygen levels may increase the risk of hypoxemia for this population, the authors noted.   

This article was referenced in an FDA safety communication issued in February 2021.⁵ The agency notified patients and healthcare providers that pulse oximeters “have limitations and a risk of inaccuracy under certain circumstances.” They were advised to not rely solely only on pulse oximeters to assess oxygen levels and to be aware that factors such as poor circulation, skin pigmentation, skin thickness, and skin temperature can affect pulse oximeter readings. Additionally, the FDA specified that over the counter (OTC) pulse oximeters, which saw increased use due to COVID-19, do not undergo FDA review and are not intended for medical use.