Pulse Oximeters Confirmed to Be Biased for Black Kids

Tested against a gold standard, the widely accessible pulse oximetry technique turned out to overestimate arterial oxygen saturation in Black kids, researchers reported.

Among children with true hypoxemia according to directly measured arterial blood oxygen saturation (SaO₂ <88%), a discordant finding of normoxemia by peripheral oxygen saturation levels on pulse oximetry (SpO₂ ≥92%), or a false negative, reached 12% of Black versus 4% of white patients, Halley Ruppel, PhD, RN, of the University of Pennsylvania in Philadelphia, and colleagues reported in JAMA Pediatrics.

Conversely, among patients with normal SpO₂ readings, 5% of Black children and 1% of white children turned out to have hypoxemia by SaO₂, Ruppel and colleagues added.

The unadjusted bias, or difference in values between SpO₂ and SaO₂, was 2.58 (95% CI 2.15-3.00) for Black patients compared with 0.89 (95% CI 0.64-1.15) for white patients (P<0.001).

"Results of this cross-sectional study using data from a highly controlled clinical environment with tightly coupled SaO₂ and SpO₂ values suggest that pulse oximetry overestimated arterial oxygen saturation in children of Black or African American race," Ruppel and colleagues concluded based on their study of children who had undergone cardiac catheterization at Children's Hospital of Philadelphia.

Concerns surrounding the accuracy of pulse oximeters for people of color came to the fore during the pandemic, when studies suggested that Black patients with COVID-19 may have experienced delays in care due to potentially inaccurate readings. A look at the pre-pandemic era revealed similar issues as well. Outside experts to the FDA recently advised that the agency work with manufacturers of the devices to address this problem.

The racial discrepancy is thought to be attributable to light absorption properties of melanin in darker-skinned individuals.

"In its current state, pulse oximetry risks underestimating disease in both adult and pediatric populations with darker skin pigmentation, when true readings could require more aggressive management when interpreted in the appropriate context," Erich Huang, MD, PhD, of Verily Life Sciences in South San Francisco, California, and colleagues wrote in an accompanying editorial.

The editorialists cited active work in the technology sector to address skin-tone bias in pulse oximetry. Two examples are photoacoustic imaging and polarized light oximetry.

Huang and colleagues warned, however, that "although technologic refinement will undoubtedly yield solutions for the issue of bias in oximetry, inclusiveness must become a broad imperative in our regulatory frameworks -- both in the initial approval of devices and in how we surveil real world application of technology."

To complete the retrospective, electronic health record (EHR)-based study, Ruppel and colleagues sought the records of children who had undergone a cardiac catheterization at Children's Hospital of Philadelphia from 2016 to 2021.

Only cases where SaO₂ was measured from a location reflective of systemic arterial saturation were included in the report. SpO₂ had to have been captured at 1-minute intervals in the EHR and linked to arterial blood gases processed immediately via co-oximeter. The researchers added that they included the first SaO₂ measurement per patient matched with an SpO₂ value within 1 minute of the SaO₂ measurement.

The study cohort ultimately included 774 patients, of which 26% were Black or African American (mean age 6.6 years) and 74% were white (mean age 7.3 years). Fifty-one percent of the Black patients were female, and 43% of the white patients were female.

The most common diagnoses in both groups were the heart defects of hypoplastic left heart syndrome/single ventricle, tetralogy of Fallot, and patent ductus arteriosus, Ruppel and colleagues reported.

"Future studies in children should prospectively evaluate the association between SpO₂ and SaO₂ with reliable, direct measurement of skin pigmentation," the researchers said.

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