Google Pixel Watch 3
Google has provided a little more detail on how its potentially life-saving “loss of pulse” detection feature works in the Pixel Watch 3.
Earlier this month, Google announced loss of pulse detection for the Pixel 3, and has now published a blog post explaining in a little more detail how it works, and how it was developed. I’ll give you the shortened version.
Google says the Pixel Watch 3’s loss of pulse feature relies on three core metrics.
The first is, sensibly enough, that the optical heart rate sensor on the back of the watch appears to detect the loss of heart rate signal. Or, to use Google’s own wording, the Pixel Watch notices “a sudden large drop in the alternating current (AC) component of the green PPG.”
It also employs a “machine learning algorithm” that analyzes the sensor data from the PPG heart rate sensor and accelerometer. And it assesses input from an “additional sensor” using LEDs with “different geometries, wavelengths, LED currents, and photodiode gain settings.”
The only explanation that really makes sense here is Google is referring to the sensor what would otherwise tell you your blood oxygenation.
Google says it teamed-up with cardiac electrophysiologists and their patients for the development of the loss of pulse feature, and no doubt the “machine leaning algorithm” its explanation refers to.
The blog goes on to explain this was a key part of the feature’s development, as recreating actual situations where someone’s heart stops is both ethically and practically fraught.
To get your head around the power of the Pixel Watch 3’s loss of pulse feature, the blog also offers some useful context. It’s about turning an “unwitnessed” out-of-hospital cardiac arrest (OHCA) into a witnessed one.
But instead of a person nearby doing that witnessing, the wearable does. As detailed in the original story on the Pixel Watch 3’s loss of pulse functionality, attempts are made to alert the wearer, using sound and haptic feedback, before a call is finally made to emergency services.
