Pulse Oximetry: Examining Racial Bias in a Valuable But Flawed Tool


For patients who require additional oxygen therapy, the levels administered often depend on a person’s oxygen saturation, which is measured by pulse oximetry. However, because this technology was developed in non-diverse populations, racial bias can affect the accuracy of pulse oximeter readings. Accordingly, using these devices to determine triage needs and adjust oxygen levels could increase the risk of hypoxemia in black patients compared to non-black patients

In a study recently published in the New England Journal of Medicine, Dr. Michael W. Sjoding, Assistant Professor in the Department of Pulmonary and Intensive Care Medicine at the University of Michigan Medical School at Ann Arbor, and colleagues used this option in patients who received supplemental oxygen at numerous locations

Sjoding et al. Analyzed 10,789 pairs of measurements of oxygen saturation by pulse oximetry and arterial oxygen saturation in arterial blood gas from 1333 white patients and 276 black patients at the University of Michigan Hospital. In addition, they analyzed 37,308 pairs of 7342 white patients and 1050 black patients in intensive care units in 178 other hospitals.

They found occult hypoxemia in 11.7% of the black patients (95% CI, 8.5% -16.0%) – defined as arterial oxygen saturation of less than 88% despite an oxygen saturation of 92% to 96% in the Pulse oximetry White patients (95% CI, 2.7% -4.7%) in an unmatched analysis of the University of Michigan cohort. Similar results were found in additional analyzes taking into account age, gender and cardiovascular risk as well as after excluding patients with diabetes or elevated carboxyhemoglobin levels.

In the multicentre cohort, unadjusted analyzes showed occult hypoxemia in 17.0% of the black patients (95% CI, 12.2% -23.3%) and 6.2% of the white patients (95% CI, 5.4 % -7.1%). 1

“Black patients in two large cohorts had almost three times the incidence of occult hypoxemia that was not detected by pulse oximetry than white patients,” wrote Dr. Sjoding et al.1 These results have some important implications, particularly during the current 2019 coronavirus disease (COVID-19) pandemic. “

Since pulse oximetry determines oxygen levels based on how much light is transmitted through the skin, the darker skin tones in black patients are likely the reason for the discrepancy found in the study, Dr. Sjoding in a recent interview. “Melanin likely changes the relationship between the amount of light it lets through and oxygen levels.”

The racial variability in risk observed underscores the need to consider other clinical and patient-reported data indicative of oxygen levels, as well as pulse oximetry readings, said Dr. Sjoding and his co-authors. In a broader sense, these results underscore the need to clarify and address the racist prejudices associated with medical devices.

While pulse oximeters can provide valuable information, healthcare professionals should be aware of the incomplete accuracy of these devices and avoid relying too heavily on them in making clinical decisions. Until the devices are corrected, healthcare providers must be aware that a device with a reading of 92% can mean that the patient’s true oxygen levels are between 88% and 96% and in some cases can be more extreme, especially those with darker skin. Dr. Sjoding advised.

A relatively simple technical solution could potentially increase the accuracy of the pulse oximeter readings in all patients, but this would require redesigning these devices. “I think health care providers need to take a stand and push to make sure this happens,” said Dr. Sjoding.

In a letter published in the Lancet Respiratory Medicine in March 2021, a group of intensive care trainees from the United States and the United Kingdom (Hidalgo et al.) Called for rapid reform in this area, noting that the differential inaccuracy of pulse oximeters had been reported since the 1990s.2 They cited this problem as “an example of systemic racism in health care that has not been addressed despite decades of evidence”.

Although the US Food and Drug Administration (FDA) recently published information about the limitations of pulse oximeters and relevant recommendations for doctors and patients, Hidalgo et al. These efforts are inadequate.2,3 They urged the FDA and other regulatory agencies to conduct a review of these devices and reserve approval for devices with equivalent performance regardless of race.

Additionally, the authors urged pulmonary and critical care societies to test rigorous pulse oximeters by regulators and urged hospitals to only buy pulse oximeters that were shown to work equally well on color patients. 2

While pulse oximeter redesign will ultimately be required to correct for racial inaccuracies, “bedside adjustment may be the least bad approach in the short term until a concrete solution is found,” wrote Philip et al. In a letter published in BMJ in February 2021 in response to the results of Sjoding et al.4 They pointed out that “there is no obvious reason why oximeters should not be calibrated on darker skin and set up at the bedside for readings that come from lighter skin. “


1. Sjoding MW, Dickson RP, Iwashyna TJ, Gay SE, Valley TS. Racial bias in the pulse oximetry measurement. N Engl J Med. 2020; 383 (25): 2477- 2478. doi: 10.1056 / NEJMc2029240

2. Hidalgo DC, Olusanya O, Harlan E. Intensive care trainees call for a reform of pulse oximetry. Lancet Respir Med. Published online March 1, 2021. doi: 10.1016 / S2213-2600 (21) 00102-8

3. Pulse Oximeter Accuracy and Limitations: FDA Safety Communications. US Food and Drug Administration. February 19, 2021. Accessed March 31, 2021.

4. Philip KEJ, Tidswell R, McFadyen C. Racial Bias in Pulse Oximetry: Other statistical details may help solve the problem. BMJ. 2021; 372: n298. doi: 10.1136 / bmj.n298

This article originally appeared on Pulmonology Advisor



Robert Dunfee