These findings add to the growing body of evidence about pulse oximetry inaccuracies in people of color, says the study’s co-lead author Ashraf Fawzy, MD, MPH, an assistant professor of medicine at the Johns Hopkins University School of Medicine in Baltimore. “Our research is the first to show that the overestimation of oxygen saturation among Black and Hispanic patients led to a delayed recognition of the need for COVID-19 therapy compared with white patients,” says Dr. Fawzy. That’s because oxygen saturation levels are often used to determine whether or not certain more aggressive COVID-19 medications are used, as some treatments are only recommended for people whose oxygen saturation levels have dropped below a certain threshold. The consequences of these inaccuracies — failure to receive appropriate treatment or delays in treatment — should be examined as potential explanations for disparities in COVID-19 outcomes, according to the authors. Black and Hispanic people are 70 percent and 80 percent more likely to die of COVID-19 than white people, respectively, according to an April 2022 report from the Centers for Disease Control and Prevention (CDC).
Many People With COVID-19 Have Low Oxygen Levels, a Life-Threatening Condition
Healthy people have an oxygen saturation of between 95 and 100 percent. Many people with COVID-19 have low oxygen levels, which can be a life-threatening condition, according to the CDC. Warning signs of low oxygen include trouble breathing, confusion, difficulty staying awake, and bluish lips or face. Adults with low oxygen saturation may also have chest pain that doesn’t go away. Some people can have a low oxygen level and show no symptoms or warning signs, which is why pulse oximetry is typically performed. The CDC recommends oxygen therapy to any COVID-19 patient with any warning signs of low oxygen or if their pulse oximeter reading is 90 percent or less.
Oxygen Levels More Likely to Be Overestimated in Black and Hispanic People
Researchers initially focused on data from 1,216 COVID-19 patients who had been given two different tests that measure blood oxygen levels: pulse oximetry and arterial blood gas (ABG) tests. A pulse oximeter is a clip-on device that’s placed on the finger, toe, or earlobe to measure oxygen saturation, or the percentage of oxygen in the blood; ABG tests require a blood sample for a direct measurement. Most patients take only a few, if any, ABG tests during an extended hospital stay — the less-invasive pulse oximeter is used much more frequently, according to the authors. The team compared the patients’ ABG test results with their pulse oximetry results and found that pulse oximetry overestimated blood oxygenation in racial and ethnic minorities. Compared with white patients, pulse oximetry overestimated blood oxygen levels by 1.2 percent for Black patients, 1.1 percent among non-Black Hispanic patients, and 1.7 percent for Asian patients. To estimate the effect of this bias, the team then looked at more than 6,673 other patients with COVID-19; 352 people were Asian, 2,642 were Black, 1,170 were Hispanic, and 2,509 were white. After applying a statistical prediction model, researchers found that more than 1 in 4 of the COVID-19 patients — the majority of whom were members of racial or ethnic minorities — probably qualified for additional COVID-19 therapy before the pulse oximeter identified it. Black patients were 29 percent less likely and non-Black Hispanic patients were 23 percent less likely to have their treatment eligibility recognized by pulse oximetry compared with white patients.
Because of Inaccurate Oximetry Results, Black and Hispanic Patients Are Less Likely to Receive Appropriate COVID-19 Treatment
These findings are important given the large role that pulse oximetry has played in determining which patients are given certain COVID-19 medications; even a small inaccuracy could keep a patient from qualifying for more aggressive therapies, according to the authors. Remdesivir, an antiviral medication that was initially authorized to treat hospitalized COVID-19 patients, is typically given only to patients with an oxygen saturation of 94 percent or less, or those who are on supplemental oxygen. Similarly, the corticosteroid dexamethasone is often used only for COVID-19 patients who require supplemental oxygen. Overestimation of oxygen saturation may also cause a person to be taken off COVID-19 therapy or even discharged from the hospital sooner than they should be, the authors wrote. “While the inaccuracy of pulse oximeters has been known and recently reiterated, our study demonstrates that there’s a clinical consequence to this inaccuracy that may impact how nonwhite patients are treated,” says Fawzy. A paper published in December 2020 in the New England Journal of Medicine found that Black patients were three times more likely than white patients to have low oxygen levels that were missed by pulse oximeters. The authors of that study estimated that as many as 1 in 10 oximetry readings for Black patients may be inaccurate.
Doctors and Patients Need to Be Aware That Pulse Oximeters May Be Less Accurate in People of Color
“Recognizing that pulse oximeters are less accurate among racial and ethnic minority patients is the most immediate step that medical practitioners can take,” says Fawzy. This knowledge may lead them to decide to pursue further testing, such as an arterial blood gas test, particularly in cases where an inaccuracy is suspected, he says. “It’s also important for patients to be aware of this when using a pulse oximeter at home, or to appropriately advocate for themselves in healthcare settings,” he says. In the long-term, pulse oximeters need to be reengineered to address this inaccuracy, which would improve care delivery for patients of color, says Fawzy.
