Google Pixel 3’s heart rate viewer
One of the Google Pixel Watch 3 smartwatch’s more novel features has just cleared the FDA, loss of pulse detection.
The feature is already available in the UK and Europe, but will begin rolling out to Pixel Watch 3 owners in the U.S. “at the end of March” according to Google.
This health and safety feature might be compared to the SOS and fall sensor features seen in other watches. When the Pixel Watch 3 detects a loss of pulse, it can raise the alarm to emergency services and send a message to your emergency contacts.
As noted in Google’s summary of the feature from back in August 2024, it won’t do this immediately. It will ask the user to respond to an alert, and if that is ignored, the Pixel Watch 3 will escalate to an audio alarm before making the final step of contacting emergency services.
It’s intended not just to potentially save lives of those who suffer a hear attack, but “respiratory or circulatory failure, overdose or poisoning” too.
How Pixel Watch 3’s Loss Of Pulse Works
One of the key difficulties in making this feature useful from a technical perspective is in minimizing the effect of false positive pulse loss readings. Google says it relies on an AI algorithm developed using “hundreds of thousands of hours of real-life user data from a diverse group of people.”
It was also tested using “stunt actors” who wore tourniquets to simulate loss of pulse, and then performed the sort of fall or motion that might come with such a real event.
The Pixel Watch 3, like just about all other wearables, primarily uses light sensors and green LEDs to tell a person’s pulse. Varying levels of reflected light indicates the relative blood flow in the vessels in the underside of a person’s wrist.
In the event of a possible loss of pulse, the Pixel Watch 3 will also use the heart rate sensor’s red LEDs to search for a pulse. These are typically used to determine blood oxygenation rather than simple heart rate.
Google’s Loss of Pulse might be seen as a natural evolution of the irregular heartbeat notification feature seen in some Pixel, Fitbit and Garmin watches, among others. And, with any luck, it could help save some lives going forwards. Google claims it’s a “first-of-its-kind” feature.