Pulse Oximetry More Likely to Miss Hypoxemia in Black Veterans than White Veterans Among General and Surgical Inpatients

BACKGROUND:
Variation in the accuracy of pulse oximetry by race in critically ill patients has been reported as early as 1990. Recent investigations have documented differential pulse oximetry measurement accuracy between Black and White patients in intensive care units and in critically ill patients with respiratory failure, with Black patients having a higher prevalence of occult hypoxemia, defined as a low arterial blood gas (i.e., SaO₂ < 88%) despite seemingly normal pulse oximetry (i.e., SpO₂ ≥ 92%) compared to White patients. The objective of this multicenter, retrospective cohort study was to evaluate measurement discrepancies by race between pulse oximetry and arterial oxygen saturation as measured in arterial blood gas (SaO₂) among inpatients not in the intensive care unit. Using VA data, investigators identified 30,039 pairs of SpO2 - SaO2 readings made within 10 minutes of each other among general medical and surgical VA inpatients from 2013 – 2019. The primary outcome was occult hypoxemia (SaO2 < 88% despite pulse oximetry reading ≥ 92%), as well as race and ethnicity.

FINDINGS:

• There was a significant difference in the ability of pulse oximetry to detect clinically relevant hypoxemia in patients of different races. Black Veterans had higher odds than white Veterans of having occult hypoxemia noted on arterial blood gas but not detected by pulse oximetry (unadjusted rates of 20% vs 16%, respectively). The absolute adjusted probability of occult hypoxemia was 4% higher in Black Veterans than in White Veterans.
• Measurements of racial differences in occult hypoxemia are not sensitive to differences in the timing of the arterial blood gas and the recorded pulse oximeter readings, up to at least 10 minutes apart.
• Findings suggest that even if a recent arterial blood gas did not show occult hypoxemia in a Black patient, an elevated index of suspicion may be warranted in Black patients with compatible signs and symptoms until unbiased pulse oximeters are routinely available.

IMPLICATIONS:

• There may be a role for large integrated health systems, such as VA, to use only pulse oximeters proven to provide equivalent accuracy in Black patients rather than devices of unproven equity.
• No oximeter brand information was available for this study. However, the majority of commercially available oximeters use similar technology.

LIMITATIONS:

• Since skin color is not consistently recorded as part of the medical record, race was used as a surrogate which might not fully reflect the skin tone diversity within each patient group nor other differences that might contribute to pulse oximetry bias.

AUTHOR/FUNDING INFORMATION:
This study was partly funded by HSR&D (IIR 17-045). Drs. Iwashyna and Prescott are part of HSR&D’s Center for Clinical Management Research (CCMR).

Valbuena V, Seelye S, Sjoding M, Valley T, Dickson R, Gay S, Claar D, Prescott H, and Iwashyna T. Racial Bias and Reproducibility in Pulse Oximetry among General Care Medical and Surgical Inpatients in the Veterans Health Administration 2013-2019: A Cohort Study. The British Medical Journal. July 6, 2022;378:e069775.