NEJM Journal Watch
Bruce Soloway, MD, reviewing
In a large cohort study, pulse oximetry missed hypoxemia more often in Black patients than in white patients.
In critical care units, pulse oximeters are less likely to detect hypoxemia in Black patients than in white patients, and undetected hypoxemia is associated with worse clinical outcomes, including higher mortality (NEJM JW Gen Med Mar 15 2022 and Crit Care Med 2022; 50:204). Are there similar disparities with pulse oximetry in patients who are not critically ill? Researchers analyzed the electronic records of all general care medical and surgical inpatients in U.S. Veterans Affairs hospitals between 2013 and 2019; they identified pairs of pulse oximeter and arterial blood oxygen readings (i.e., SpO2 and SaO2, respectively) taken in the same patient within 10 minutes of each other. Occult hypoxemia was defined as a pair in which the pulse oximetry reading was >92% but directly measured arterial oxygen saturation was <88%.
Among 30,000 pairs analyzed, 73% were from white patients, and 22% were from Black patients. Occult hypoxemia was significantly more likely to occur in Black than in white patients (19.6% vs. 15.6%, respectively). Among patients who had concordant pairs early in the day, the probabilities of occult hypoxemia being noted in a pair taken later in the day were 12.9% and 2.7% for Black and white patients, respectively.
These data demonstrate that, for Black general inpatients compared with white general inpatients, pulse oximetry is both biased (systemically underestimating hypoxemia) and unreliable (one accurate test was less likely to predict an accurate second test). Oximeters that are accurate across a range of skin tones are being developed but are not yet clinically available. Until they are, clinicians who are assessing possible hypoxemia in Black patients might need to consider drawing arterial blood more often.
Valbuena VSM et al. Racial bias and reproducibility in pulse oximetry among medical and surgical inpatients in general care in the Veterans Health Administration 2013-19: Multicenter, retrospective cohort study. BMJ 2022 Jul 6; 378:e069775. (https://doi.org/10.1136/bmj-2021-069775)