Pulse Oximeters - Do they work for everyone? Nope!

When the COVID-19 pandemic started in early 2020 one of the main measurements being used to triage people within the hospital systems in the United States was blood oxygen saturation (Valbuena et. al, 2021). This measurement tells providers how much oxygen is circulating with your red blood cells. For a healthy individual, your blood should be 95 - 100% saturated with oxygen and anything below this range raises cause for concern. During the pandemic, this measurement has been directly translated to how well a patient’s lungs are doing their job and if a patient needs further evaluation.

This value is collected by a machine known as a pulse oximeter. They are small devices that pinch your finger into a clamp-like structure and shine a light through your skin. This light allows the machine to view the blood vessels in a person's finger and see how much oxygen is floating through the vessels. It is able to do this through light absorbance spectrophotometry, where the oxygenated hemoglobin absorbs light at 660 nm and deoxygenated absorbs light around 940 nm (Jubran, 2015). The device is then able to take the ratio of the two measurements give a percent saturation (Jabran, 2015). Quite incredible! 

However, these devices have been researched on an almost exclusively the white population whose skin is more translucent. During the pandemic the FDA came out with a statement explaining that the pulse oximeter machines on the market could be inaccurate for those with darker skin tones. Shortly after the FDA also stated they were working on creating inclusive and diverse clinical trials for medical products for the future. How is this concern just being addressed now? In a recent study testing for occult hypoxemia, arterial oxygen saturation of less than 88%, they gathered 10,789 pulse oxygen readings and compared the accuracy of readings from white patients vs balck patients (Valbuena et. al, 2021). What they found was black patients are more at risk of having undiagnosed hypoxia because they were three times as likely to not have it detected by the pulse oximeter than their white counterparts (Valbuena et. al, 2021). This is not the first study to bring this disparity to light; there are studies much like this one dating back into the early 2000s (Phillip et. al, 2005). It took until 2020 for the FDA to address this concern of racial inequality. The United States claims to be a mixing pot of people of all backgrounds, yet medical devices are only catering to a subset of the population? Where is the justice in this? We need to do better especially for those most affected by this pandemic. My hope is that the FDA will come out with more news, but as of yet nothing has been published and they are only advising providers not to use pulse oximeter measurements as part of the diagnosis process of COVID-19. 

Sources: 

Commissioner, O. O. (2020, November 9). FDA Offers Guidance to Enhance Diversity in Clinical Trials, Encourage Inclusivity in Medical Product Development. Retrieved November 15, 2021, from: https://www.fda.gov/news-events/press-announcements/fda-offers-guidance-enhance-diversity-clinical-trials-encourage-inclusivity-medical-product

Jubran A. (2015). Pulse oximetry. Critical care (London, England), 19(1), 272. https://doi.org/10.1186/s13054-015-0984-8  

Philip E. Bickler, John R. Feiner, John W. Severinghaus; Effects of Skin Pigmentation on Pulse Oximeter Accuracy at Low Saturation. Anesthesiology 2005; 102:715–719 doi: https://doi.org/10.1097/00000542-200504000-00004 

Valbuena, V. S. M., Barbaro, R. P., Claar, D., Valley, T. S., Dickson, R. P., Gay, S. E., Sjoding, M. W., & Iwashyna, T. J. (2021). Racial Bias in Pulse Oximetry Measurement Among Patients About to Undergo Extracorporeal Membrane Oxygenation in 2019-2020: A Retrospective Cohort Study. Chest. https://doi-org.dml.regis.edu/10.1016/j.chest. 2021.09.025