Apple Watch Series 6 – Why Watch Your Blood Oxygen?

This week apple released the Apple Watch Series 6. The premier feature is the pulse oximetry sensor on its underbelly that measures peripheral blood oxygen saturation (SpO2).

I love Apple products. In fact, in the past I’ve suggested that if Apple released an Apple Hat I would buy it. Despite my blind love for all things Apple I began to wonder this week why we need a watch that measures oxygen saturation?

A pulse oximeter looking for problem

Great minds think alike. Brian Chen in the New York Times looked for someone to tell him why the average person needs pulse oximeter (love the title: The New Apple Watch Measures Your Blood Oxygen: Now What?)

Nice story. But no solid answer.

When experts in the New York Times have to squint and cock their head to rationalize a piece of technology, it’s the sign of a solution looking for a problem. Of course, post-facto we can always reconstruct the hard indication. But even with an unlimited budget, I’m not sure there’s anyone who would identify our inability to measure SpO2 as a problem to be solved.

(I’ll add that Apple will find the indication. The press releases will come involving isolated cases where the Apple Watch Series 6 SpO2 sensor saved a life. And some will point to these cases as evidence that we are in trouble without a wrist-borne oxygen sensor.)

Management of serious lung disease: Don’t try this at home

Despite ambiguity around why we need this, Twitter was abuzz this week with speculation about how Apple Series 6 could revolutionize the care of folks with COPD and asthma. But Apple has made it very clear that this is a wellness application and it’s not intended for medical management.

The reason we wouldn’t consider the Apple Watch SpO2 reading as medical grade is its ‘reflective’ sensor (also used in the Garmin and FitBit) and its location. A standard pulse oximetry probe sends red and infrared light through the tip of the finger where there’s lots of blood. Based on how much of each kind of light gets through to the receiving sensor on the other side of the finger, the level of oxygen in the blood is calculated. As it turns out, the reflective sensor on the wrist is less sensitive than the medical strength fingertip sensors and it’s also subject to interference from light and watch position.

So don’t try to manage your advanced lung disease at home.

I would add that unlike silent arrhythmias where a patient is asymptomatic (making watch-based arrhythmia detection potentially higher impact), it’s more likely that those near a tipping point with COPD or reactive airway disease will have symptoms that offer some kind of alert.

Apple Watch Series 6: Emerging applications

So where could Apple Watch Series 6 SpO2 monitor make a dent? I suspect it might shine in the identification of obstructive sleep apnea (OSA) which is commonly under diagnosed. While my symptoms have improved dramatically after losing 50 lbs, I still snore some (so my wife says) and wonder how mild OSA could be impacting my sleep quality.

Despite its insistence on Apple Series 6 as a wellness tool, it is interesting that Apple has used deliberate language that nudges dangerously close to suggesting the watch’s potential role in the early detection of acute respiratory infection from flu and COVID-19. Blood oxygen and pulse oximetry are terms that we’ve heard a lot about during the COVID pandemic, said Sumbul Ahmad Desai, Apple’s VP of well being. They do report having a study underway with the University of Washington testing the watch’s sensitivity for early COVID detection.

Sure, it’s a wellness app but rest assured that Apple has its eyes on bigger medical things.

Context is health information’s greatest challenge

So putting this new watch into the broader perspective….

When we train young doctors we challenge them with this question when they want to order a test: What are you going to do with the information?

Consumers are facing the same question but they don’t know to ask it.

We faced this with the ECG feature in 2018 and now with SpO2 monitoring. What does it the information on my wrist mean and what do we do with the information? And who is really prepared to help patients make sense of their data?

This is where the democratization of diagnostics has come up a little short.

Clinical information can only be understood in the context of an individual’s broader story. And to be clear, it isn’t that patients shouldn’t be measuring. It’s just that health data without wisdom is just a spreadsheet. It would be better if there were solid resources to help them make sense what they find. And it would be even better if we gathered information with purpose and intent.

This idea of helping patients contextualize their records, data and anatomic reports will represent then next big wave following implementation of the ONC’s Cures Act this fall. I’ve been thinking a lot about this so stay tuned.

But I love to be wrong

In fairness none of us really know how a technology will be used until it’s set free. Clive Thompson has suggested that a tool’s most transformative uses generally take us by surprise. With that said I love to be wrong when it suits my patients and the empowered health consumer. Let the free digital health market do its thing. And tell us how Apple’s O2 sensor changed the course of your life.

I’m currently wearing a Series 4. Despite the skepticism you’ll find below, I suspect I’ll pick one up. I’m curious about my sleep patterns. As you’ll read, I have to consider how I’m going to make sense of what it tells me since I could wind up more confused than empowered.

Would love to know what you think. Or your experience with the watch.

If you like this you might like to check out other 33 charts stuff written about the Apple Watch. In fact, every post here has hand selected tags listed at the very bottom of every post that will guide you to related material. Check it out.
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