Due to pulse oximeters' subpar performance, people of color receive less supplementary oxygen in the ICU, a research found.
According to research by Eric Raphael Gottlieb, MD, MS, of Brigham and Women’s Hospital in Boston, and colleagues, average oxygen delivery rates were lower for Asian, Black, and Hispanic patients than for white patients.
When controlling for average respiratory rate, initial blood carbon dioxide level, number of blood gas tests early in the admission, haemoglobin level, and need for vasopressors or inotropes, they reported in JAMA Internal Medicine that this averaged out to about 0.2 to 0.3 L/min less oxygen for those groups.
The authors highlighted that the inconsistency between haemoglobin oxygen saturation and pulse oximetry (SpO2) appeared to be at fault. After accounting for the discrepancy between the average haemoglobin oxygen saturation and average SpO2, the relationship between race and ethnicity and oxygen delivery rate vanished. Since the devices use transmission of near-infrared light, which can be impacted by skin melanin, to estimate blood haemoglobin oxygen saturation, their limits in individuals with darker skin have been well known for decades.
The clinical implications of hidden hypoxemia are now clear, wrote Eric Ward, MD, of the University of California San Francisco, and Mitchell H. Katz, MD, of NYC Health + Hospitals in New York City, in an accompanying editor’s note. They pointed to another recent study showing that pulse oximetry overestimated oxygen saturation by more than 1 percentage points in minority groups with COVID-19, leading to delayed recognition of eligibility for treatment.
FDA has said it will call an advisory committee meeting later in 2022 on pulse oximeter accuracy in people with darker skin pigmentation.
While the agency has suggested that regulation could be on the table, the editorial note called this disparity “particularly troubling” because “device development and data interpretation are firmly within the control of the health care sector.”
Healthcare systems can be part of the solution as one of the major markets for pulse oximeters, Ward and Katz noted. “If they make a commitment to buy only devices that function across skin tones, manufacturers would respond.”
It’s an issue that will only become more important with the advent of closed-loop circuits that automatically titrate supplemental oxygen based on SpO2, the researchers wrote.
“Our findings present a unique and compelling opportunity to improve equity through device reengineering and by reevaluating how data are interpreted,” they added, suggesting it would be ideal to correct SpO2 readings based on objective colorimetry, not reported race or ethnicity.
The retrospective cohort study included 3,069 patients (mean age 66.9) in Beth Israel Deaconess Medical Center’s Medical Information Mart for Intensive Care (MIMIC)-IV critical care data set who spent at least 12 hours in the ICU before needing advanced respiratory support. Among them, 2,667 were white, 112 were Hispanic, 207 were Black, and 83 were Asian patients.
Because the data spanned from 2008 through 2019, the study didn’t address COVID-19 patients. The findings were also limited by the single institution, examination of only cannula oxygen delivery, without data on titration of a fraction of inspired oxygen or temporally-matched hemoglobin oxygen saturation values. Time off oxygen was likely under-reported, race and ethnicity were self-reported, and no assessment was made of skin tone.
“Further research is needed to confirm these findings and explore other clinical factors associated with treatment disparities,” the researchers noted.
Parvathy Sukumaran 
