Disparities in Hypoxemia Detection by Pulse Oximetry Across Self-Identified Racial Groups and Associations With Clinical Outcomes

Abstract

Objectives: To assess disparities in hypoxemia detection by pulse oximetry across self-identified racial groups and associations with clinical outcomes.

Design: Observational cohort study from May 5, 2018, to December 31, 2020.

Setting: Three academic medical centers in the United States.

Patients: Adults greater than or equal to 18 years who self-identified as White, Black, Asian, or American Indian admitted to the ICU or undergoing surgery during inpatient hospitalization with simultaneous measurements of pulse oximetry-estimated oxygen saturation and arterial blood gas-derived oxygen saturation.

Interventions: None.

Measurements and main results: Multivariable models were employed to assess the relationships between race, occult hypoxemia (i.e., arterial blood gas-derived oxygen saturation < 88% despite pulse oximetry-estimated oxygen saturation ≥ 92%), and clinical outcomes of hospital mortality and hospital-free days. One-hundred twenty-eight-thousand two-hundred eighty-five paired pulse oximetry-estimated oxygen saturation-arterial blood gas-derived oxygen saturation measurements were included from 26,603 patients. Pulse oximetry-estimated oxygen saturation on average overestimated arterial blood gas-derived oxygen saturation by 1.57% (1.54-1.61%). Black, Asian, and American Indian patients were more likely to experience occult hypoxemia during hospitalization (estimated probability 6.2% [5.1-7.6%], 6.6% [4.9-8.8%], and 6.6% [4.4-10.0%], respectively) compared with White patients (3.6% [3.4-3.8%]). Black patients had increased odds of occult hypoxemia compared with White patients after adjustment (odds ratio, 1.65; 1.28-2.14; p < 0.001). Differences in occult hypoxemia between Asian and American Indian patients compared with White patients were not significant after adjustment (odds ratio, 1.53; 0.95-2.47; p = 0.077 and odds ratio, 1.31; 0.80-2.16; p = 0.288, respectively). Occult hypoxemia was associated with increased odds of mortality in surgical (odds ratio, 2.96; 1.20-7.28; p = 0.019) and ICU patients (1.36; 1.03-1.80; p = 0.033). Occult hypoxemia was associated with fewer hospital-free days in surgical (-2.5 d [-3.9 to -1.2 d]; p < 0.001) but not ICU patients (0.4 d [-0.7 to 1.4 d]; p = 0.500).

Conclusions: Occult hypoxemia is more common in Black patients compared with White patients and is associated with increased mortality, suggesting potentially important outcome implications for undetected hypoxemia. It is imperative to validate pulse oximetry with expanded racial inclusion.

Figure 1.

Scatterplot of estimated peripheral oxygen saturation by pulse oximetry and arterial blood gas-derived oxygen saturation across self-identified racial groups Bubble size is determined by the proportion of the total sample according to race. The dotted lined represents arterial oxygen saturation less than 88% as representation of true arterial hypoxemia.

Figure 2.

Estimated probability of occult hypoxemia for a 55-year old patient for any given pulse oximetry value across racial groups Hypoxemia defined as arterial blood gas derived oxygen saturation (SaO₂) <88%. SpO₂ is the estimated peripheral oxygen saturation as derived from pulse oximetry. Data shown for a hypothetical 55-year old patient without vasopressor requirement or home oxygen use.

Figure 3.

Boxplots of paired oxygen assessments for White and Black patients The dotted lined represents arterial oxygen saturation less than 88% as representation of true arterial hypoxemia.