Pulse oximeters remain an invaluable medical device – but a new study suggests there’s plenty of room for improvement.
Researchers at Brigham and Women’s Hospital and Beth Israel Deaconess Medical Center found inadequacies in care at one local ICU because of falsely optimistic readings among some racial groups on pulse-ox tests.
The retrospective study compared the pulse oximeter readings of more than 3,000 patients admitted to the Beth Israel ICU between 2008 and 2019, with actual blood oxygen measurements and the resultant care. The study appears in JAMANetwork.
“Asian, Black and Hispanic patients averaged higher oxygen levels measured by pulse oximeter for a given blood level of oxygen,” said study co-author Eric Gottlieb, MD, MS, now a physician at Mt. Auburn Hospital in Cambridge. “And then these patients received lower rates of supplemental oxygen.”
Pulse oximeters use light waves, passed through a finger or ear lobe, to detect the level of oxygenation in the blood. The quick and painless test is in contrast to the invasive, but more accurate way, of measuring blood oxygen – by drawing blood from the radial artery.
While pulse oximeters have been a medical staple for nearly 50 years, some raised questions decades ago about their accuracy in non-Caucasians.
“The main thing we found and we published back in 1990 was pointing out that it was far less accurate in black patients than in white patients,” said Martin Tobin, MD, a Chicago pulmonologist. “Basically, it has remained the same since then.”
That research, published in the journal Chest in June 1990, found Black patients commonly suffering from hypoxia, or low blood oxygen levels -- even with pulse-ox levels that suggested adequate oxygenation. The study also found pulse-ox inaccuracies more than twice as likely in Blacks than in Whites.
“If the primary measure you’re using to decide how severe the low level of oxygen is a pulse oximeter -- and if it’s two and a half times less accurate in Black people than in white people, then you’re going to have problems,” said Tobin.
It’s likely problems attributable to pulse-ox inaccuracy popped up during the pandemic, as Tobin suggested.
“I doubt if the (COVID-19) illness was necessarily different in the Blacks than in the whites,” Tobin said. “But the management is going to be different if the primary tool you’re using is less accurate.”
Gottlieb said it seems possible delays in treatment for COVID among certain racial groups may also be connected to falsely optimistic pulse-ox readings.
While the pulse oximeter remains an invaluable medical tool, it contains a central flaw, said Tobin.
“The pulse oximeter works extraordinarily well,” Tobin said. “It’s an amazing device. Because I practiced medicine before there were any pulse oximeters. But the calibration, the software within the machine, is based on measurements obtained in white people.”
So what’s the solution?
“I think the most important thing is to improve the pulse oximeters,” Gottlieb said. “And I think that’s really exciting. Because when we see this disparity in care between patients, a lot of times there are policy changes that you need to think about, sometimes very controversial issues. But in this case it’s taking advantage of engineering to make a pulse oximeter that reads more consistently across patient groups.”
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