Pulse oximeters, widely used medical devices, are shown to give inflated oxygen saturation readings in individuals with darker skin tones, according to a recent groundbreaking study published in the British Journal of Anaesthesia. 

The study, the most extensive of its kind, reviewed 44 studies spanning from the mid-1970s to the present, analysing over 733,000 oxygen saturation readings from more than 222,000 people, including nearly 70,000 individuals of non-white ethnicity.

The research reveals a consistent tendency for pulse oximeters to overestimate readings in participants with darker skin tones. 

Although the precise magnitude of these overestimates remains challenging to determine based on existing data, researchers emphasise the potential consequences for both patients and medical professionals.

Issues arising from overestimation include patients being perceived as healthy based on inaccurate readings, potentially delaying necessary medical attention. 

This is particularly critical, as the study suggests errors are more pronounced at lower levels of oxygen saturation, putting individuals with critical oxygen levels at risk of not receiving urgent treatment.

The study, led by Professor Daniel Martin OBE, includes experts from various UK universities and hospitals specialising in intensive care medicine, dermatology, and paediatric care. 

Underlining the importance of accurate data for informed clinical decisions, especially during the COVID pandemic, where thresholds were established for hospital admissions based on oxygen saturation levels, Professor Martin said, “As clinicians, we rely on accurate data to make informed clinical decisions. But during the COVID pandemic, and to some extent since, it was necessary to put thresholds in place which meant that people were only admitted to hospital if their levels fell to a certain point. If those levels are being overestimated – so, for example, if a device is telling someone their oxygen saturation is 98% whereas it is in fact significantly lower – it could realistically mean people are missing out on treatments they need.".

Pulse oximeters, initially designed for hospital use, are now widely employed in various healthcare settings, including GP surgeries, outpatient departments, emergency rooms, and intensive care units. Additionally, they are available for public purchase and self-monitoring of oxygen saturation levels.

Pointing out that other safety mechanisms exist in hospitals, such as blood tests unaffected by skin tone, community reliance on pulse oximeters for health assessments raises concerns, Prof Martin added, “If people are admitted to hospital, there are other safety mechanisms to help identify unwell patients. Blood tests to measure oxygen levels, for example, will not be impacted in any way by a person’s skin tone and a medical appointment will allow a doctor or nurse to carry out a physical assessment as well as other types of monitoring. The concern is that there may be people in the community relying on pulse oximeter readings to signify a deterioration in their health, where these additional tests are unavailable.”

Highlighting the importance of clinicians considering a person's skin tone in decision-making when using pulse oximeters, co-author Professor Eugene Healy, said, “This systematic review highlights the need for clinicians to take account of a person’s skin tone as part of the clinical decision-making process when using pulse oximeters to estimate oxygen levels.” 

The findings from the systematic review are being further explored through the EXAKT study, funded by the National Institute for Health and Care Research (NIHR). 

The study is recruiting around 900 critically ill patients with diverse skin tones from 24 UK sites to investigate the accuracy of specific pulse oximeters used in hospitals today.