Clinical question: Are there disparities in hypoxemia detection by pulse oximetry across self-identified racial groups and, if so, is there an association with clinical outcomes?
Background: Previous studies have suggested racial disparities in pulse oximetry-measured oxygen saturation (SpO2) because differences in skin pigmentation affect the accuracy of spectrophotometry. Consequently, pulse oximetry is more likely to overestimate arterial oxygen saturation (SaO2) for patients with darker skin. Those studies were limited by smaller size, the time delay between SpO2 and SaO2 measurements, and the lack of assessment of clinical outcomes.
Study design: Observational cohort study
Setting: Three academic medical centers in the United States
Synopsis: This study included 128,285 simultaneous measurements of SpO2 by pulse oximetry and SaO2 by arterial blood gas (ABG) from 26,603 ICU and surgical patients and showed that occult hypoxemia (SaO2 < 88% despite SpO2 ≥ 92%) occurs more frequently in black as compared with white patients, odds ratio (OR) 1.65 [1.28-2.14], p < 0.001. The incidence of occult hypoxemia was highest at low-normal SpO2 values. There were no significant differences in occult hypoxemia for Asian and American Indian patients when compared to white patients after multivariable adjustments. Occult hypoxemia was associated with increased hospital mortality in surgical (OR 2.96 [1.20-7.28], p < 0.019) and ICU patients (1.36 [1.03-1.80], p < 0.033) as well as fewer hospital-free days in surgical (-2.5 d [-3.9 to -1.2 d], p < 0.001) but not ICU patients.
These findings warrant further research into quantification or adjustment for skin pigmentation, noting that race was self-identified in this study.
Bottom line: Black ICU and surgical patients experience increased occult hypoxemia compared to white patients, and occult hypoxemia is associated with increased hospital mortality. Clinicians should consider direct evaluation of SaO2 at low-normal SpO2 values in black patients to assess for occult hypoxemia.
Citation: Henry NR, et al. Disparities in Hypoxemia Detection by Pulse Oximetry Across Self-Identified Racial Groups and Associations With Clinical Outcomes. Crit Care Med. 2022;50(2):204-211. doi:10.1097/CCM.0000000000005394
Dr. Long is a second-year internal medicine resident at Maine Medical Center, Portland, Maine.