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?
Budget Medical Devices
One of the amazing things about technological progress is that sensors and processing capabilities that were rather exotic a few decades ago are now being included in just about any smart device you can strap on your wrist. This includes motion sensors, pulse- and oxygen level meters, making these devices in theory capable of acting like ambulatory cardiac monitors and similar medical devices that monitor health parameters and respond to emergencies.
While for a long time the gold standard for heart function monitoring over a longer period outside a hospital setting involved a portable electrocardiogram (ECG) recorder, recently wrist-worn monitoring devices based around photoplethysmography (PPG) have proven themselves to be acceptable substitutes. In a 2018 study by Francesco Sartor et al. in BMC Sports Science, Medicine and Rehabilitation the researchers found that the wrist-worn PPG was not as accurate as the ECG-based chest strap monitor, but came close enough to be practical.
Here the difference is such that applications where precision actually matters the chest strap ECG is still the optimal choice, but wrist-worn PPG devices as integrated into many fitness bands and smart watches are an acceptable substitute, such as when monitoring heart rate for signs of atrial fibrillation. A 2022 study by Christopher Ford et al. in JACC: Clinical Electrophysiology examined two smart watches (Apple Watch 4, KardiaBand) for this purpose, finding that their accuracy here was 91% and 87% respectively.
Together with additional sensors like the commonly integrated motion sensor, these devices seem accurate enough to at least determine whether the person wearing them is suffering a cardiac event that requires immediate intervention.
Health Check
The idea of an automatic emergency call isn’t new, with for example the EU making such a system (called eCall) mandatory in new cars since 2018. The idea is that when a serious collision is detected, emergency services are contacted and provided with location and sensor data. Google added its Car Crash Detection feature to the Pixel 3 smartphone in 2019, and Apple added Crash Detection to its Apple Watch and iPhones in 2022. These use sensor data from gyroscopes, GPS, microphones, and accelerometers to determine whether a crash just occurred.
What users of these devices discovered, however, was that activities such as going on a rollercoaster ride could activate this feature, as well as snowmobile rides, skiing, and similar activities. In response, Apple had to adjust its algorithms on these devices to reduce the number of false positives. Despite this, rescue workers in e.g. Canada are still reporting a large number of false positives. One reason cited is that although there’s a time-out before emergency line is called with audible alarm, this can be hard to hear when you’re on a snowmobile.
As it turns out, defining what seems like a pretty clear event to us when you’re limited to just this handful of sensors is much trickier than it seems. After all, what is different between the sensor data from a rollercoaster ride, a car crash, dropping one’s phone or smart watch onto a concrete floor or forgetting said phone on the roof of the car?
In this context, the idea of taking a simple activity like measuring heart rate and pulse, and extrapolating from these that if they cease, an emergency has occurred is fraught with pitfalls as well.
Merging Data
How do you know as a human being that someone has just suffered cardiac arrest? You confirm that they don’t have a noticeable carotid pulse, and the reason why you checked is because they clearly collapsed. This is when you’d pull out your phone and dial emergency services. The LoPD feature that Google has introduced has to do effectively exactly these steps, except that it starts from the loss of pulse (LoP) rather than from seeing someone pass out and collapse to the ground.
Thus the tricky part is establishing whether said collapsing has occurred, not whether the pulse has been lost. After all, the user may have simply taken the watch off. According to Google, to verify their algorithms they hired stunt actors to simulate LoP using a tourniquet, cutting off blood flow, and simulating falls like a person suffering cardiac arrest would suffer.
On the sensor side they use the heart rate monitor (PPG sensor), which initially uses the green light to check for pulse, but can switch to infrared and red lights when a LoP condition is triggered. Simultaneously the motion sensor data is consulted, with a lack of motion taken as a sign that we’re dealing with a LoPD. This starts an auditory alarm and visual countdown on the screen before emergency services are contacted with an automated message plus the user’s location.
Then they needed to calibrate the response to this merged sensor data with clinical data on cardiological events before trialing the result with said stunt actors and volunteers. An article on this research was also published in Nature (paywalled, but here is a gift article), detailing the algorithm and the way they tested its effectiveness. In the paper the authors note one false positive event and subsequent emergency call across 21.67 user-years across two studies, with a sensitivity of 67.23%.
A Matter Of Time
In the case of cardiac arrest, time is of the absolute essence. This is also clearly noted in the Google paper on the LoPD feature, who note that ideally there is a witness on-site who can immediately begin CPR or ideally get a nearby automated external defibrillator (AED). Unfortunately in most cases of cardiac arrest, this event goes initially unnoticed. The LoPD feature on a smart watch thus would be for cases where nobody is around to notice the emergency and respond to it. Although it isn’t explicitly mentioned, it seems that the watch can also detect whether it’s being worn or not, which should prevent false positives there.
With over half a million US citizens each year suffering cardiac arrest, and over half of these occurring outside of a hospital setting, this could potentially save thousands of lives each year. Following cardiac arrest and in the absence of resuscitation the lack of blood and oxygen being circulated means that within minutes organs begin to suffer the harmful effects, depending on their oxygen requirements. The brain is generally the first to suffer ill effects, which is why the application of CPR is so crucial.
Because of the intense urgency following a major cardiac event like this, the practical use of this LoPD feature will be highly dependent on the location where the emergency occurs. In the case of someone collapsing while alone at home in their city house or apartment, this could conceivably save their life if emergency services can arrive within minutes. Even faster and more useful in less urban settings would probably be having your smart device notify nearby people who can then perform CPR while calling 911 or equivalent.
That said, perhaps the real killer feature that’s missing here is an integrated AED in smartphones since everyone has one of those things on them at all times, or even smart watches that can automatically perform defibrillation while also notifying emergency services.
Remind me not to have a cardiac arrest when sitting in a chair…
I know of someone who had one while sitting on the toilet in bathroom at night.
Must be embarassing to be found that way by the ambulance helpers.
Even worse if you had passed away just shortly before.
Sounds like Elvis
‘On the crapper’ is in the top 10 of situations died in.
Is common.
super common to the point of not even eliciting comment from the EMTs. That may make you feel better or worse. That’s on you.
As a long-time medic it’s fairly common and we don’t think twice about it.
It’s just “oh, ok, here’s where it happened” & you carry on like it’s nothing. Because, to you, it’s nothing
Remind me not to buy any of these devices in the first place… A phones a phone, a watch is a watch. KISS.
Imagine a phone that is also a calculator, alarm clock, text message interface, would be crazy talk, nobody wants that….
That’s a PDA, silly! 😆 Aka palm pc, pocket pc, handheld pc.
3com Palm Pilot had been in common use since 1996!
https://en.wikipedia.org/wiki/PalmPilot
Nowadays “smartphone” are just PDAs with a cellphone modem tacked on!
Not creative, at all. We had them years before the iPhone.
There were Nokia Communicator, T-Mobile MDA, Handspring Treo 160,
the Siemens SX-45 (based on Casio Cassiopeia E-125) and many more.
In fact, the iPhone might have been inspired by a Palm OS device.
The Handspring Visor had an optional 2G cellphone module for Springboard slot.
The people of Handspring even demoed it to Mr. Jobs, according to a documentary,
who then was convinced to center everything around a phone instead of a Mac.
This. The Treo was a great phone/PDA and before that a usable albeit less integrated phone module for the Handspring Visor. Apple followed by merged a phone into their iPod Touch unit which was a large screen iPod music and app device.
KISS means “keep it simple and stupid”.
These smart watches can be bad to wearers of pacemakers/defibrillator under some circumstances.
Because the electric sensor pulses may trigger the pacemakers unnecessarily.
The optical sensor method is not problematic, though.
Actually it is “Keep it Simple Stupid” :) . Just a little difference in meaning :) .
https://en.wikipedia.org/wiki/KISS_principle
I agree.
Although with the “smart” devices revolution ranging from toasters to coasters the concept of a “stupid” device makes sense. Therefore the definition of KISS could very evolve in “keep it simple and stupid”. I can see it happen.
Can’t speak for others but my heart stopped beating once and it was anything but subtle. Apple watch ECG caught it and that earned me a 2 week cardiac event monitor.
Regarding the AED idea – they have pacemakers with build in defibs for patients who need that. You don’t really want a phone OS doing those things.
My father had a pacemaker with defibrillator.
The defibrillator kicked in once – for real, really required.
It saved his life.
The next visit with his heart doctor after he got out of the hospital, he had the defibrillator function turned off.
The experience of being defibrillated while conscious was so ghastly that he decided he’d rather die than go through that again.
Die he did, the next time the defibrillator would have kicked in.
The one defibrillator experience extended his life by several months. Whatever he experienced that one time was apparently bad enough that not even extra months of life was worth it.
Sorry about your dad Joseph. Can’t imagine it (waking defib) myself either. Was friends with a guy who coded in ER, got shocked, started to come around and heard “shock him again”. Said it felt like all his cells were flying apart. Closest I’ve been is respiratory failure during a procedure and waking up with incredible chest pain – not even comparable.
…I’m slow.. just now got the “killer feature” pun. Well done!
+1
A deep dive into how the AED devices work would be a good article. Acting as a defibrillator is the least of what they do, first they have to talk someone through attaching the pads correctly, then they have to analyse a heartbeat, and only if it detects fibrillation does it fire.
Fun fact, it can take at least a minute for the heart to start up after a defib, so you really need someone there performing CPR as soon as possible.
Just got my cert. Defibs have made it virtually dummy proof to save someone’s life, but what they won’t do is start a heart that has stopped beating. They are designed to listen for the pulse and shock the heart back into sinus rhythm. If there isn’t a detectable electrical signal, you need to perform CPR (unless the patient is in the ER). Portable defibrillator devices don’t have enough wattage to jump-start a heart. Apparently the paddles at the ER are putting out a LOT of amperage.
One false positive per 20 user-years is huge. With a million users, that gives 140 false calls per day.
And the problem is? Right, poor support for people working in healthcare.
Working as, say, an ambulance helper or carer in the nursing home should be rewarded. Both socially and financial.
There’s something deeply wrong in modern society that such social-oriented people aren’t being welcomed with open arms.
We need them more than ever, and we needed them to be uplifting
and positive. Which won’t happen if they’re being mistreatet lik sub-humans.
But if they are negative and unhappy, they are likely to loose engagement and merely work for the little bit of money.
To make life excellent to all of us, people should be encouraged to work in social activities.
There should be an overcapacity of people working at call centers,
be it in case a big catastrophe happens or for sake of them being well rested.
Same goes for education sector. Children should be raised in a way by their parents and family members early on that they show at least a minimum of respect to teachers.
They don’t have to “obey” but at least behave normally.
“Working as, say, an ambulance helper or carer in the nursing home should be rewarded. Both socially and financial.”
I see you have jokes.
EMS will hire the cheapest person with the least amount of experience, as those who burn out leave, since they are easy to replace.
Those that make a lifetime of it either a) have had extremely easy on shift or b) are mentally ready to just crumble.
There are lots of jobs basically only for kids (e.g. HVAC crawlspace/attic monkey. Garbage truck maintenance tech. etc etc)
They pay pretty well, because they suck so hard.
Once you’ve got any other decent choice you’re gone.
IMHO Joshua is a middle schooler.
Frequent use of ‘should’ is the tell.
He thinks anybody ‘wipes elder ass’ for anything but money in the first place.
I’m going to write a HaD article about what I’m calling “The Denominator Problem.” basically this. you know someday.
The comment section for that one will be fun, looking forward to it
“as nobody wants to regularly apologize for a false alert to the overworked person staffing the 911 or equivalent emergency line” … I have called 112 (I’m Dutch – 112 is the European emergency number) dozens of times and they have all been extremely cool.
I’ve called them to test new VOIP installations, about large items on the driving lanes of the highway (heavy ratchet straps, wooden beams), a car that drove 30 km/h on the motorway, a generator that heavily smoked which I saw from the highway in a pinewood forest in dry conditions (“Yes, we’ve had hundreds of calls about that. This one has been checked and is ok, but please keep calling for similar events”), a traffic jam in an unexpected place with obscured view, and once about someone who had made a suicide attempt (fortunately a failed one). Each and every time they were really cool, and for the more minute things I asked them whether that was ok to call them for it “Yes, that’s perfectly fine!”.
I notice there is some fear about calling 112 for things where noone is actually dying right now, I think instilled into children for not calling that number as a joke. When in doubt, I think it’s always better to call emergency services.
Dutch too. Called 112 for someone I presumed heavily injured at the very least. Operator thought it was a prank call because I sounded like a kid.
Did you start with “Hi, I’m Dj Biohazard”?”
We had 1922 in Germany for calling an emergency doctor, but it nolonger worked last time I tried in an emergency.
Instead a new number should have been called instead, to manage the calls. Modernization or something. Or lack of personell.
However, the computer voice held me in a telephone queue.
For 20min – and it was a real emergency.
After that, I hung up and called 112 (firebrigade in Germany, 110 is/used to be police) and got a human being on the phone, who then called the ambulance at hospital real quick.
If we hadn’t been lucky that someone was there doing the cardiac massage and mouth-to-mouth resuscitation already, that unconscious person wouldn’t have made it because I had to wait on phone.
Long story short: Time matters. If you can’t get through, consider try calling police or firebrigade or any other emergency service.
They can make contact with their colleagues.
112 is (and has been for decades) the central emergency number in Germany for both fire and ambulance. I had never heard of 19222 being a thing, so I looked it up. It was apparently for “Krankentransport”, which is just for transporting somebody to the hospital, not neccessarily in a medical emergency (non-livethreatening situations, basically), and in the last decades it was active (until… 2004, or thereabouts) you had to dial the local area code as well. As I wrote: I had not heard about this number (and I’m… old), and I might be wrong, because, hey, only cursory search on the internet. Could be a variation from state to state (Bayern? they like doing things differently ;) ).
Reading a bit more about emergency numbers, like on
https://www.drk.de/das-drk/geschichte-des-roten-kreuzes/112-die-nummer-fuer-den-ernstfall-eine-kurze-geschichte-des-rettungsdienstes-zum-europaeischen-tag-des-notrufs/ (in German), tells me that 112 has been the emergency number since the 70s in the FRG (while in the GDR it was 115).
But to emphasise your last point: yes, do call any known working emergency service number. They will forward the call, time counts. I have friends who are dispatchers and first responders, and they would rather you call them than dieing.
And another remark: As far as I know, many cell phones are intelligent enough to call the correct number (i.e. 110 in the EU) even if you dial 911.
I’ve heard that 911 works on land-line phones as well, even south of the Weisswurstgrenze. But needless to say, I haven’t verified it just for funsies.
My Nokia 3310, when locked, would dial 112 even when you typed (or pocketdialed) 911, but in the USA would dial 911 when calling 112.
Cell phones don’t call 911 or 112, they initiate a call in a special emergency mode and the base station routes it to the local emergency service.
So…. the tech for the DocWagon Super-Platinum account is here?
So all we need now is the service itself, with people who have proverbial balls of tungsten to rescue you from anywhere. ^^’
Last paragraph:
“That said, perhaps the real killer feature that’s missing here is an integrated AED in smartphones since everyone has one of those things on them at all times, or even smart watches that can automatically perform defibrillation while also notifying emergency services.”
1) “killer feature”- Interesting choice of words given the topic!
2) AEDs, along with non-automated external defibrillators, work by passing hundreds of volts ACROSS the heart to restore rhythm. For external defibrillation to work, the paddles/pads are placed on either side of the heart specifically so current flows through/across the heart. Defibrillation is not as simple as just shocking the body. So… even if watches or phones had enough battery capacity as well as the circuitry to boost to hundreds of volts, no single device strapped to your wrist or in your hand could ever really perform defibrillation as we know it. Implanting electrodes in/around the heart can resolve the challenge of getting the current to flow along the required physical path, but at that point a dedicated pacemaker variant makes way more sense than relying on your smartphone/watch to be the defibrillator controller….
Well this is clearly an opportunity for smart clothing, right? Conductive fibers in the right places. Also works for ensuring good behavior.
Maybe it would be a good idea if we could get an affordable emergency kit that includes a cheap defibrillator, CPR kit, and a small fire extinguisher. Like a bug out bag that can be stuffed in a trunk. The really important part is getting the AED cost down, as they cost quite a bit and I personally think it’s ridiculous to have a simple device by price locked by FDA bureaucracy. It’s not a new idea anymore, R&D isn’t a factor, and getting it medically cleared shouldn’t take as long or cost as much as it currently does.
I’m sorry, but for a literal life saving device, you need a properly manufactured device, not the latest Temu deal.
We’ve recently had another recall of a series of AEDs after incidents where they didn’t shock when they should have, and that’s from a known brand.
sometimes i wonder if life saving features are there so that you live long enough to buy the next version.
i could do with fewer death stealers. after observing the way the world treats old people i dont want to live past 50.
50 is better than the alternative
50? Don’t be silly. You’re still a boy at that age.
Don’t eat crap, or smoke, and restrict alcohol to special occasions rather than a regular part of your diet, and with a modicum of reasonable exercise it won’t be until you hit your mid 70s that you’ll start to notice age.
I’m afraid your idea of “old” is a bit off kilter. Dude, you’ll miss out on all of the good senior discounts if you check out at 50.
Most people are decrepit before they die.
Doesn’t really matter what age that is…50 fits right in with constant heavy drinking, crap food.
But you’ll be sick and decrepit by 40, spend a good chunk of your youth hungover and get 5 2s (rather then any 10s).
Buy your ticket, take your chances.
My first impression seeing this is that it’s a great setup for a Black Mirror episode.
Life-saving features are great, but I’m quite curious if it works in practice. Even with GPS, the watch can only give the approximate location. In a densely populated area, there is very little chance of finding the person. Hopefully it’ll work and save many lives.
As for the black mirror part, it’s an interesting technology to monitor your heart rate 24/7. But I’m not looking forward to the heart rate being coupled to other data. I can only guess what Google can do with it at scale.
I was finally able to disable the smartwatch emergency calling “feature”… Last time it called 911 when using power tools. Before that, dozens of times during enjoyable bicycle rides. Not a convince…
Now I can give data aggregation companies access to my heart rate, respiration rate, and galvanic skin response so they can align it with my realime gps location and accelerometer data for “linger time” at any given location!
Why wouldn’t I want my physiological impression data associated with whatever thing I happen to be standing next to?
How else are the marketing companies going to generate ads on demand, specifically for me, if they don’t know my subconscious preferences for fonts/colors/kerning?
A quick back of the envelope calculation:
The article mentions half a million cardiac arrests in the US a year, of which roughly half happen outside a hospital (in which case the watch would have been useful). On about 300mi US citizens, that’s an average of 1/1200 of these cases per wearer per year. With the reported 67% sensitivity, thats about 1/800 rightful emercency calls per user-year.
Compare that to the reported 1 false positive per 22 user-year, and it becomes clear the vast majority of calls will be false positives.
The problem is the baselines. Most people wearing these will not suffer cardiac arrest, which is why you get so many false positives.
Don’t get me wrong, I love this kind of tech, and hope it will save many lives. But it has to work well enough.
Too bad Defibrillation doesn’t really work the way it does in the movies. We could have that watch that restarts your heart like in that one James Bond movie.
Imagine a watch virus.
Distributed to the DNC daily talking point mailing list.
When it detects the user dying, Trump appears on their phone to taunt them, one last time.
Good laughs!
Some would get so mad, they don’t die.
Live on as zombies, powered by hate, voting D forever.
First off let me be the first to say this Maya Posch article is actually ok-ish. I usually dunk all over them (till I got my comments consistently banned) but at least you did a decent job and finally defined your acronyms/abbreviations. Thanks for that.
second
Hello professional medical person here. For 20+ years starting with being an EMT in college and up through current profession that I don’t care too much to define here.
I’ve done plenty of CPR, in and out of hospital etc. The out of hospital survival rate for CPR with a non-professional rescuer is like… 2% or something last I looked [citation needed]. In hospital it is way better, all the way to maybe 10, 15% but that really really depends on how you look at survival. on a vent with maxed out drips for that night? sure. “meaningful outcome” like back to playing bridge with the group on Thursdays? naw. rare.
The comment above about someone turning off the AICD (automatic implantable cardiac defib.) rings true to those elderly etc I’ve had the honor to speak with. Thinking everyone over 50 is useless and in constant misery is also way, way too far to one side of the argument and clearly wasn’t made by someone staring 50 in the eye currently.
I could go on forever, but as someone that has seen it all, or most of it, I’ll say you will never, ever see me wearing a device that monitors my vitals constantly and phones home and all that. My watch ticks. My razor needs sharpening, and I try to live a life such that if I shuffle off this mortal coil I leave happy that I wasn’t too much of an f-up before I went. Preserving life at all costs (my definition of “alive” is very gray compared to most other people) is subject to a lot of further discussion. anyway.
Good enough for me, your experience probably varies.
This and the Apple watch are really impressive, it’s just a shame the only option is to join Apple’s walled garden or have all your most intimate data uploaded by Google if you want to make use of them.
Or is there some decent less evil option I don’t know about – perhaps the revived Pebble?
I can’t afford health insurance, so don’t let me know when I’m dying please.
I wonder what the chances are of emergency services arriving within the short window while you can still be saved without significant brain damage?
Small I would think.
Still, it will prevent people laying dead for weeks in their home I suppose, that is not uncommon I understand.
Doesn’t do much for the wearer but saves the sanitation people at least.
Can be used by the military of course, knowing where your men are dying ‘live’ migh be a morbid but useful thing in (AI controlled) battles that you might see in the future.
I can also think of a few ways this technology can be used nefariously, I hope the ‘usual suspects’ don’t think of it too.