Pixel Watch 3’s Loss Of Pulse Detection: The Algorithms That Tell Someone Is Dying

More and more of the ‘smart’ gadgets like watches and phones that we carry around with us these days come with features that we’d not care to ever need. Since these are devices that we strap onto our wrists and generally carry in close proximity to our bodies, they can use their sensors to make an estimation of whether said body is possibly in the process of expiring. This can be due to a severe kinetic event like a car crash, or something more subtle like the cessation of the beating of one’s heart.

There is a fairly new Loss of Pulse Detection (LoPD) feature in Google’s Pixel Watch 3 that recently got US FDA approval, allowing it to be made available in the US after previously becoming available in over a dozen European countries following its announcement in August of 2024. This opt-in feature regularly polls whether it can detect the user’s pulse. If not found, it cascades down a few steps before calling emergency services.

The pertinent question here is always whether it is truly detecting a crisis event, as nobody wants to regularly apologize for a false alert to the overworked person staffing the 911 or equivalent emergency line. So how do you reliably determine that your smart watch or phone should dial emergencies forthwith?

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Flying Defibrillators

It’s a sad reality that, by and large, cardiopulmonary resuscitation (CPR) doesn’t save lives. Despite all the “you could save a life” marketing aimed at getting people certified in CPR, the instances where even the prompt application of the correct technique results in a save are vanishingly rare, and limited mostly to witnessed arrests in a hospital. Speaking from personal experience, few things are sadder than arriving on-scene as a first responder to see CPR being performed by a husband on his wife and knowing that no matter what we do, it’s not going to end well.

The problem is one of time. Hearts only rarely just stop beating outright; usually some kind of arrhythmia first causes the heart to beat ineffectively, leading to hypoxia and loss of consciousness. From there it’s about a four-minute trip to brain death, but in that brief window chances are pretty good that the heart can be restarted. That’s why witnessed cardiac arrests in a hospital have better survival rates — the needed electric reboot of the heart with a defibrillator is only as far away as the nearest crash cart.

The advent of the automatic external defibrillator (AED) has increased the odds for survival of out-of-hospital cardiac arrest (OHCA), but the penetration of AEDs into public settings is far from complete enough to put one within a few minutes reach of everyone who might need one. So it’s only natural that thoughts would turn to delivering AEDs to cardiac incidents by drones. It seems like a great idea, but will it work? Continue reading “Flying Defibrillators”