An Update to Your Fitbit Could Detect a Covid-19 Symptom
By: Thomas Smith
Tags: Health, Wearables, Fitbit, Tech, Coronavirus

An Update to Your Fitbit Could Detect a Covid-19 Symptom

You might have a full-featured pulse oximeter sitting on your wrist right now

Photo: Adam Birkett/Unsplash

One of the scariest things about Covid-19 is that if you get the virus, there’s not a whole lot you can do. Official guidelines say to treat it at home, much as you would a cold or flu — rest, drink fluids, separate yourself from others in your living space, and so on.

That’s all well and good, except that Covid-19 has fast developed a reputation for causing otherwise stable patients to crash alarmingly quickly. Doctors tell stories of patients who battle the virus for days or weeks, seem fine, and then in a matter of hours deteriorate and need to be placed on a ventilator — or worse.

If you’re treating yourself for Covid-19 at home, how can you know if you’re in the middle of a serious crash? By all accounts, Covid-19 makes many people feel terrible — how can patients outside a hospital setting know when things have gone from merely awful to life-threatening?

One potential health tool that’s rapidly emerging is the use of a home pulse oximeter. These simple devices measure the oxygen level in your blood. If it drops below 92%, that’s a concern. If it falls further, you could be in big trouble — some Covid-19 patients have reportedly had levels in the 50% range.

Pulse oximeters are especially appealing because Covid-19 has been reported to cause silent hypoxia. In this condition — which seems tailor-made to haunt the dreams of hypochondriacs — a person can walk around with a serious Covid-19 oxygen deficiency and not know about it until it’s too late.

There’s only one problem — home pulse oximeters are fast becoming more scarce than toilet paper. I got an Innovo pulse oximeter a year ago to monitor myself during exercise. I paid $23 for the device, and it arrived in two days. This morning, I checked Amazon and could only find one pulse oximeter available to ship in less than a week. They were charging $60. Most wouldn’t ship until mid-May, or later, at any price.

If you’re one of the millions of people who wear a Fitbit smartwatch, though, there’s good news. You likely have a full-featured pulse oximeter sitting on your wrist right now. And it could be one firmware update away from potentially saving your life.

That Fitbit has been quietly placing pulse oximeters in their watches for years has long been a badly kept industry secret. Users and gadget reviewers alike have noticed the sensors on the back of their Fitbit devices and speculated about their presence and function. A video on my own low-budget YouTube channel speculating about the sensor has 10,000+ views and has received more viewer engagement than many of my other videos.

The consensus (which Fitbit ultimately confirmed) was that the company was quietly developing a program to use the sensor for detection of sleep apnea. As early as 2017, Fitbit was hinting at this direction and copped to testing hardware for detecting apnea (a serious condition, the treatment of which will be a projected $6.7 billion industry by 2021). As Fitbit rolled out improved sleep tracking last year, a move toward tracking sleep apnea seemed just over the horizon (I was a beta tester in this program).

There are several hurdles to including a pulse oximeter in a consumer wearable. First, there are the technical hurdles. The device has to actually work, and measuring oxygen levels at the wrist is a challenging problem. Some data also indicates that it’s especially challenging with people of color, a concerning finding, especially since Covid-19 impacts these communities disproportionately. There are also concerns that a user’s movements could impact the readings — although, silent hypoxia aside, it’s unclear how much a Covid-19-afflicted patient would be moving around. And price is always a concern — smartwatches often cost $150+, putting them out of reach of many vulnerable populations.

Rather than treating blood oxygen as another vanity metric to show to life hackers and exercise fanatics, it’s gone the much-harder route of using its sensors to work toward diagnosing an actual medical condition.

But beyond the technical challenges, there are also major regulatory hurdles to clear. Telling people their step count (or even their heart rate) is one thing. Diagnosing them with a disease using a consumer device is another entirely. My own best guess is that Fitbit, as an independent company, didn’t have the regulatory connections and pocketbook to stomach a move into the medical device sector.

With its announced acquisition by Google, though, Fitbit suddenly has a deep-pocketed corporate parent to navigate the U.S. Food and Drug Administration (and handle the liability from potential device failures) on its behalf. Perhaps because of that backing, Fitbit quietly rolled out blood oxygen level tracking in its app in January and told Gizmodo that it “expect[s] to submit for FDA clearance soon.”

Fitbit’s new blood oxygen measurement capability has potentially life-saving implications in the fight against Covid-19. Twenty-eight million people already wear Fitbits, so using them as pulse oximeters could provide monitoring capabilities to a huge swath of people at once (the capability is not available in all Fitbit models, but is present in its newer smartwatches and trackers). Blood oxygen levels are more useful in a diagnostic sense when they’re used to track a trend. What better way to see oxygen level trends than to have an always-on pulse oximeter on your wrist?

At the moment, Fitbit only exposes oxygen level data in the sleep-tracking portion of its app. The levels are used to show a general summary of oxygenation status, and users can’t get a specific percentage reading. This is consistent with its original goal of tracking sleep apnea.

But that’s likely a firmware and software decision, not a hardware one. A simple firmware update over the air could likely enable full blood oxygen level tracking very easily, since the hardware (and likely the algorithms for processing raw pulse oximeter readings into meaningful data) are already there.

So will Fitbit enable this feature? A lot likely depends on regulatory bodies like the FDA. The FDA reportedly did not allow Apple to enable its own blood oxygen level tracking on the Apple watch, another popular device with a stealth pulse oximeter onboard. But it did hint at allowing consumer wearables to monitor for Covid-19, and researchers are forging ahead with studies to evaluate the Apple Watch, Fitbit devices, and Garmin smartwatches for this purpose. At the moment, Fitbit still says its devices shouldn’t be used for medical purposes. And there are the ongoing technical concerns about the devices’ accuracy, especially at the low oxygen levels that indicate danger.

Here, though, Fitbit’s cautious approach and years of testing may serve it well. Rather than treating blood oxygen as another vanity metric to show to life hackers and exercise fanatics, it’s gone the much-harder route of using its sensors to work toward diagnosing an actual medical condition.

That means the company has likely been laying the groundwork for medical device clearance — technically and legally — from day one. That gives it a huge advantage over its competitors, both in terms of regulatory connections and the hardware already baked into millions of its devices.

That the condition Fitbit chose to treat, sleep apnea, is characterized by low oxygen levels bodes well, too. The company has likely focused on detecting oxygen accurately at low levels from the beginning. This potentially gives it another major boost over other smart devices, which work best at measuring the high oxygen levels exhibited by healthy users. It may even give Fitbit’s devices an advantage over existing, FDA-cleared pulse oximeters, which likely use more basic software and simpler algorithms to perform their measurements.

And for Fitbit’s blood oxygen levels to be useful, they don’t have to be perfect. They just need to show a meaningful trend. Rather than exposing the values as a specific percentage, the company could always give a summary statistic to indicate an overall trend or trajectory — green for “You’re fine,” yellow for “Call your doctor,” and red for “go to the ER.”

Critics of Fitbit’s tech also miss the point that its pulse oximeter readings wouldn’t have to stand alone. The company already has detailed knowledge of its users’ bodies, including their height, weight, age, heart rate trends, and overall activity levels, as well as their baseline blood oxygen levels. All this data could be integrated into a risk score for low oxygen levels — the pulse oximeter reading wouldn’t need to stand alone.

I don’t have a window into Fitbit’s tech or regulatory teams or into the FDA. But given what I know about the company’s trajectory and hardware, it seems ideally placed to rapidly provide life-saving oxygen monitoring to millions. Doing so would likely require addressing technical and regulatory (not to mention UI and privacy) issues rapidly and taking on some unknown risks.

But Fitbit has years of research under its belt. It has proven hardware, trusted by millions of users and medical industry players alike. It appears to have a relationship with the FDA, and the corporate backing, in Google and Alphabet, to intensify that relationship quickly (and address the inevitable liability concerns of fast-tracking a medical device).

If any company can bring life-saving pulse oximetry to millions of people overnight, my money is on Fitbit.