Pulse Oximeters Have a Fatal Flaw for Some People

The FDA’s warning came after a study published in the New England Journal of Medicine compared the oxygen levels recorded by pulse oximeters to those measured by arterial blood gas, which is a lot more accurate but requires an invasive procedure. The results showed that in white patients, pulse oximeters produced misleading numbers 3.6% of the time, while the number jumped to 11.7% in black patients. This means that they were three times as likely to mis hypoxemia in black patients.

The reason for the discrepancy is that pulse oximeters work by sending red light through your finger and reading it on the other side. It is essentially detecting the color of your blood to determine the oxygenation levels. Bright red is highly oxygenated, and blue or purplish blood is less oxygenated. But if the device isn’t calibrated for darker skin, the pigmentation will affect how light is absorbed.