The report is a product of the VA/HSR&D Evidence Synthesis Program.
Differential Pulse Oximeter Accuracy, Occult Hypoxemia Prevalence, and Clinical Outcomes
by Patient Race/Ethnicity: A Systematic Review
Takeaway: Pulse oximeters likely overestimate Black or African American patients' blood oxygen saturation level, increasing the risk for unrecognized or "occult" hypoxemia. Occult hypoxemia occurs to some degree in all races/ethnicities but is likely more common among Black or African American patients compared with White patients. Clinicians should be aware of the risk for occult hypoxemia in patients with darker skin pigmentation. Evidence from hospital and health system settings relevant to VA also suggests that the amount of bias in pulse oximeter readings could vary substantially from patient to patient regardless of their race/ethnicity.
Pulse oximeters are used in many clinical settings and provide a rapid and noninvasive means of measuring oxygen saturation. Despite this utility, pulse oximeters may over- or underestimate a patient’s arterial oxygen saturation (SaO2). Overestimating oxygen saturation is especially concerning when pulse oximeter readings of peripheral oxygen saturation (SpO2) indicate a normal blood oxygen level while a patient is actually in a hypoxemic state—a situation known as occult hypoxemia. Potential clinical impacts of occult or undetected hypoxemia include delayed or inadequate treatment, premature treatment de-escalation or discharge, and ultimately, greater morbidity and mortality. Differences in pulse oximeter accuracy by patient race/ethnicity have been observed in clinical settings for several decades, but the COVID-19 pandemic has heightened concern that pulse oximeters may routinely be less accurate in patients with darker skin pigmentation, in turn contributing to greater risk of occult hypoxemia.
In response to a request from VA’s National Hospital Medicine Program and Office of Specialty Care Services, HSR&D’s Evidence Synthesis Program (ESP) Coordinating Center located in Portland, Oregon, conducted a systematic review and meta-analysis of evidence on racial and ethnic disparities in the accuracy of pulse oximeters, the prevalence of occult hypoxemia, and clinical outcomes associated with occult hypoxemia.
Summary of Findings
Of the articles reviewed for inclusion, 34 primary studies and 1 existing systematic review and meta-analysis on pulse oximeter accuracy met eligibility criteria. Based on this evidence, investigators concluded that:
- Pulse oximeters likely overestimate Black or African American patients’ blood oxygen saturation levels (moderate strength of evidence), though recent studies in contemporary hospital and health system settings suggest that modern pulse oximeters possess some degree of bias and considerable imprecision regardless of patient race/ethnicity.
- Occult hypoxemia is likely more common among Black or African American patients compared with White patients (moderate strength of evidence). Compared with White patients, the prevalence of occult hypoxemia was 71% greater among Black or African American patients. Asian, Latino or Hispanic, Native American or Indigenous, or other or mixed race/ethnicity patients may also experience occult hypoxemia more frequently than White patients (low strength of evidence).
- Evidence is insufficient to draw conclusions about clinical outcomes attributable to race/ethnicity biases in occult hypoxemia, but available studies provide suggestive evidence that Black patients with undetected hypoxemia could experience poorer treatment delivery and clinical outcomes than White patients with undetected hypoxemia.
Incorporating an existing review of pulse oximeter accuracy meant that we could not exclude studies with limited relevance to modern clinical practice among Veterans (ie, studies that used older pulse oximeter technologies or pediatric samples).
Clinicians should be aware of the risk for occult hypoxemia in patients with darker skin pigmentation. Moreover, while pulse oximeter readings are on average fairly similar to arterial oxygen saturation levels, evidence from hospital and health system settings relevant to the VA suggests that the amount of bias could vary substantially from patient to patient regardless of their race/ethnicity. This finding implies that incorporating conventional race or ethnicity-based correction factors into pulse oximeters would not eliminate disparities in occult hypoxemia risk. Although proposed changes to clinical practice to accommodate bias and imprecision in pulse oximeters may help to mitigate harms in the near-term, advancements in non-invasive oximeter technology are needed. As the largest integrated health system in the United States, VA is uniquely positioned to cultivate innovations in oximeter technology.
Parr NJ, Beech EH, and Young S. Differential Pulse Oximeter Accuracy, Occult Hypoxemia Prevalence, and Clinical Outcomes by Patient Race/Ethnicity: A Systematic Review. Washington, DC: Evidence Synthesis Program, Health Services Research and Development Service, Office of Research and Development, Department of Veterans Affairs. VA ESP Project #09-199; 2023.
To view the full report, go to: vaww.hsrd.research.va.gov/publications/esp/pulse-oximetry.cfm (Intranet only).
ESP is currently soliciting review topics from the broader VA community. Nominations will be accepted electronically using the online Topic Submission Form. If your topic is selected for a synthesis, you will be contacted by an ESP Center to refine the questions and determine a timeline for the report.
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