By Jacqueline Sergon, Department of Nurse Anesthesia, University of Pittsburgh School of Nursing
As a rapid and non-invasive means of measuring blood oxygenation saturation, the modern-day peripheral pulse oximeter has come to define basic monitoring standards of nursing anesthesia care. Certified registered nurse anesthetists (CRNAs) rely upon pulse oximetry metrics in determining a patient’s oxygenation status, and whether they are a low anesthetic risk, or at greater risk for potential complications such as aspiration pneumonia, or airway obstruction- factors that subsequently influence the anesthesia plan of care.
As CRNAs, and certainly, as SRNAs (student registered nursing anesthetists), we have come to accept as scientific truth, pulse oximetry results as we see them when placed on our patients. However, long-standing research called into question their accuracy as far back as 1990, noting that Black patients were more likely than White patients to have inaccurate pulse oximetry readings (Jubran & Tubin). Additionally, researchers in this study, which examined the reliability of pulse oximetry in ventilator-dependent patients, noted that among White patients, a SpO2 target of 92% reliably predicted adequate oxygen saturation; In Black patients, however, a similar reading equated to significant hypoxemia and thus required a higher SpO2 target of at least 95% (1990). The lack of racial and ethnic diversity was concerning enough for researchers to note this in their published findings, as seen by Kelleher (1987), who stated at the time it was standard practice for dark-skinned patients to be generally excluded from clinical trial subjects.
In subsequent years, these findings remained under-publicized by the medical community and the public as a whole. Consequently, as pulse oximeters became more technologically advanced, they also became more commonplace outside the hospital due to the increased demand for medical supplies in the burgeoning home-healthcare industry. Yet, with the great technological strides being made, there was no commensurate progress on racial diversity on the part of the medical device manufacturers. This can be attributed partly, to a lack of emphasis from the FDA (Food and Drug Administration), which requires manufacturers to have only a minimum of two subjects be of dark skin (FDA, 2013), hence establishing a precedent for a low diversity threshold requirement.
The year 2020 brought forth a seismic cultural shift on two important fronts: the first was the Covid-19 global pandemic, which ushered in a massive upscale in the global demand for peripheral pulse oximeters, as more people were quarantining and self-monitoring in their homes. The other, perhaps not as commonly known, is that the pandemic, and the consequential spike in pulse oximetry demand, also provided an ideal breeding ground for clinical research into the long-held findings of racial inaccuracies in pulse oximetry. It was out of this that the ground-breaking research by Sjoding et al. emerged, in which they examined thousands of hospitalized Covid-19 patients and found that Black patients were three times more likely to have occult hypoxemia associated with inaccurate pulse oximetry readings than White patients (2020). These significant findings were published in the New England Journal of Medicine and have since been widely cited in research studies and news media articles on this topic. Of note, the Anesthesia Patient Safety Foundation (APSF, 2021) cited Sjoding’s research in its clarion call for increased diversification of clinical subjects, as well as increased collaboration amongst stakeholders such as manufacturers, government regulators, and providers in ensuring increased racial diversity of clinical subjects (APSF, 2021). And the FDA cited this research in their official safety bulletin on the limitations of pulse oximetry accuracy and the effects of skin pigmentation (2021).
The underestimation of hypoxemia in pulse ox readings has significant ramifications on clinical progression, prognosis, and patient outcomes with respect to morbidity and mortality rates. In research carried out among Covid-19 and ARDS patients about to be placed on ECMO intervention, data pointed to Black patients having a significantly higher risk of occult hypoxemia compared to White patients (Valbuena, et al., 2021). These findings mirror those of Burnett et al., who similarly found that Black and Hispanic subjects were more dispensed to intraoperative occult hypoxemia than White subjects (2022), as well as that of Henry et al., who found that patients who self-identified as either Black, American Indian or Asian were more likely than White patients to experience occult hypoxemia, and also had greater odds of mortality associated with occult hypoxemia than White patients (2022). Another research study emerging from the Covid-19 pandemic examined the racial and ethnic relational discrepancies between pulse oximetry and arterial oxygen saturation and determined that Black subjects were also more likely to suffer greater organ dysfunction, higher lactate levels, and overall greater mortality than White subjects (Wong et al., 2021). Thus far, research evidence is clear on the impact overestimation of oxygen saturation can have on clinical outcomes on these patients, in masking clinical indicators for Covid-19, pneumonia, or other respiratory disorders.
Racial inaccuracies associated with pulse oximetry use are not just an issue in the U.S. A British study (Crooks, et al., 2022) found that Covid-19 patients of Black, Asian or mixed racial ethnicity had higher oxygen saturation readings than Caucasian patients. The implications of these findings not only highlight the gravity of this issue on a global scale but reiterate the level of multi-party commitment needed to address the need for greater racial and ethnic inclusivity.
In addition to geographic impact, research shows that racial inaccuracies in pulse oximetry apply concomitantly across the entire age spectrum. This is evidenced by research on pulse oximeter accuracy among pre-term infants, which determined that there was a modest but consistent difference in oxygen saturation error between Black and White infants, with the former having higher incidences of occult hypoxemia than the latter (Vesoulis, et al., 2022). These findings serve to illuminate the far-reaching implications to CRNAs as they provide anesthesia care to patients of all age groups; as such, an awareness of these research findings can help influence anesthesia plans for better pediatric outcomes.
Given the research, an overarching theme has clearly emerged of a lack of racial and ethnic diversity in medical device manufacturing and clinical trialing. This has subsequently created a profound ripple effect, across age spectrums, socio-economic strata, and across the globe that is reflected in clinical outcomes. In today’s world, the importance of racial and ethnic diversity and inclusivity is crucial and cannot be over-emphasized, particularly when it comes to devices whose use has potential life or death consequences. As it stands, the current lack of diversity in clinical trials is enabled by a lack of government emphasis on greater diversity and racial inclusivity on the manufacturing level. Therefore, it is incumbent upon not just government regulators and medical device manufacturers to reconsider their policies and practices on racial diversity and inclusivity, but all of us as equally important stakeholders to advocate more aggressively for racial inclusivity and diversity in order to gain better representation not just for ourselves as medical providers and consumers, but for our deserving patients as well.
Crooks, West, J., Morling, J. R., Simmonds, M., Juurlink, I., Briggs, S., Cruickshank, S., Hammond-Pears, S., Shaw, D., Card, T. R., & Fogarty, A. W. Pulse oximeters’ measurements vary across ethnic groups: An observational study in patients with Covid-19 infection. The European Respiratory Journal. (2022); 59. https://doi.org/10.1183/13993003.03246-2021
FDA (2013). Pulse Oximeters – Premarket Notification Submissions [510(k)s]: Guidance for Industry and Food and Drug Administration Staff. Obtained from: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/pulse-oximeters-premarket-notification-submissions-510ks-guidance-industry-and-food-and-drug
FDA (2021). Pulse Oximeter Accuracy and Limitations: FDA Safety Communication. Obtained from: https://www.fda.gov/medical-devices/safety-communications/pulse-oximeter-accuracy-and-limitations-fda-safety-communication
Feldman, J. APSF Statement on Pulse Oximetry and Skin Tone. APSF Newsletter. (2021) https://www.apsf.org/article/apsf-statement-on-pulse-oximetry-and-skin-tone/
Henry NR., Hanson AC, Schulte PJ, Warner NS, Manento MN, Weister TJ, Warner MA. Disparities in Hypoxemia Detection by Pulse Oximetry Across Self-Identified Racial Groups and Associations With Clinical Outcomes*. Critical Care Medicine. 2022; 50 (2): 204-211. doi: 10.1097/CCM.0000000000005394
Jubran, & Tobin, M. J. Reliability of Pulse Oximetry in Titrating Supplemental Oxygen Therapy in Ventilator-Dependent Patients. Chest, (1990); 97(6): 1420–1425. https://doi.org/10.1378/chest.97.6.1420
Kelleher, J.F. (1989). Pulse oximetry. Journal of Clinical Monitoring (1990); 5(1): 37–62. https://doi.org/10.1007/BF01618369 Sjoding, Dickson, R. P., Iwashyna, T. J., Gay, S. E., & Valley, T. S. (2020). Racial Bias in Pulse Oximetry Measurement. The New England Journal of Medicine, 383(25), 2477–2478. https://doi.org/10.1056/NEJMc2029240
Sjoding, Dickson, R. P., Iwashyna, T. J., Gay, S. E., & Valley, T. S. (2020). Racial Bias in Pulse Oximetry Measurement. The New England Journal of Medicine, 383(25), 2477–2478. https://doi.org/10.1056/NEJMc2029240 Severinghaus, J.W.,& Astrup, P.B. History of blood gas analysis. VI. Oximetry. Journal of Clinical Monitoring (1986); 2, 17-288. https://doi.org/10.1007/BF02851177
Vesoulis, Tims, A., Lodhi, H., Lalos, N., & Whitehead, H. Racial discrepancy in pulse oximeter accuracy in preterm infants. Journal of Perinatology (2022); 42(1), 79–85. https://doi.org/10.1038/s41372-021-01230-3
Wong AI, Charpignon M, Kim H, et al. Analysis of Discrepancies Between Pulse Oximetry and Arterial Oxygen Saturation Measurements by Race and Ethnicity and Association With Organ Dysfunction and Mortality. JAMA Netw Open. 2021;4(11):e2131674. doi:10.1001/jamanetworkopen.2021.31674
Student Column by Jacqueline Sergon, originally published on AANA. View here.