“While pulse oximeters may be useful for estimating blood oxygen levels, these devices have limitations that can result in inaccurate readings,” Dr. William Maisel, director of the Office of Product Evaluation and Quality in the FDA’s Center for Devices and Radiological Health, said in a statement.
The researchers wanted to know how often the pulse oximeter was showing a relatively normal oxygen level when it should have been registering something more concerning.
In White patients, the pulse oximeter gave a misleading number 3.6% of the time. In Black patients, it was 11.7% of the time.
The takeaway, Dr. Sjoding says, is that pulse oximeters were three times as likely to miss significantly low oxygen levels — or hypoxemia — in Black patients. The study suggests one in every 10 Black patients may be getting deceptive results.
Why the readings aren’t precise
There’s a relatively simple explanation for why. Pulse oximeters work by sending two types of red light through your finger. A sensor on the other side of the device picks up this light and uses it to detect the color of your blood; bright red blood is highly oxygenated, while blue or purplish blood is less. If the device isn’t calibrated for darker skin, the pigmentation could affect how the light is absorbed. Dark nail polish can cause a similar effect.
Experienced physicians don’t rely on the pulse oximeter alone to make a diagnosis or decide a patient’s treatment, says Dr. Michelle Ng Gong, chief of Critical Care Medicine and the chief of Pulmonary Medicine at Montefiore Medical Center in New York.
“They would never tell a patient that I don’t care how badly you feel, as long as that number is OK, don’t worry about it,” says Dr. Gong. “It is a tool. And as a tool, we need to be able to use it properly in the context of other information.”
But, Dr. Gong says, during the pandemic, when hospitals are overwhelmed, and doctors who may not normally be in the emergency room are being brought in to see and triage patients,…