The new Apple Watch tracks blood oxygen. Now what?

The new Apple Watch can be summed up in two words: blood oxygen. The ability to measure your blood’s oxygen saturation — an overall indicator of wellness — is the most significant new feature in the Apple Watch Series 6, which was unveiled this week and becomes available on Friday. (The watch is otherwise not that different from last year’s Apple watch.) The feature is particularly timely with the coronavirus, because some patients in critical condition with Covid-19 have had low blood oxygen levels.

But how useful is this feature for all of us, really?

I had a day to test the new $399 Apple Watch to measure my blood oxygen level. The process was simple: You open the blood oxygen app on the device, keep your wrist steady and hit the Start button. After 15 seconds, during which a sensor on the back of the watch measures your blood oxygen level by shining lights onto your wrist, it shows your reading. In three tests, my blood oxygen level stood between 99 percent and 100 percent.

I wasn’t quite sure what to do with this information. So I asked two medical experts about the new feature. Both were cautiously optimistic about its potential benefits, especially for research. The ability to constantly monitor blood oxygen levels with some degree of accuracy, they said, could help people discover symptoms for health conditions like sleep apnea.

“Continuous recording of data can be really interesting to see trends,” said Cathy A. Goldstein, a sleep physician at the University of Michigan’s Medicine Sleep Clinic. But for most people who are relatively healthy, measuring blood oxygen on an everyday basis could be way more information than we need. Ethan Weiss, a cardiologist at the University of California, San Francisco, said he was concerned that blood oxygen readings could breed anxiety in people and lead them to take unnecessary tests.

“It can be positive and negative,” he cautioned. “It could keep people out of doctors’ offices and at home and give them reassurance, but it could also create a lot of anxiety.