Skip to content
Thoughtful, detailed coverage of everything Apple for 34 years
and the TidBITS Content Network for Apple professionals
A hairy man with electrodes on his chest.

I’m a Paramedic: Here’s How the Apple Watch Series 4 Will and Won’t Save Lives

I saw my first dead body in the fall of 1990. I was in Emergency Medical Technician school a couple of nights each week and on my first ride with a real ambulance crew in Boulder, Colorado. The guy’s neighbors were worried and called 9-1-1. We came and left. We didn’t know why or how this man died, just that he appeared to have fallen down due to whatever killed him, and there wasn’t anything we could do.

Later on, I finished EMT school, volunteered with a local fire department and ambulance, moved on to Paramedic school, and spent a couple of years working full-time in emergency medical services. Eventually, I scaled back to finish college and spent more time with mountain rescue and ski patrol, and on a disaster response team, which I still do today.

I’ve seen strokes from atrial fibrillation (AFib), slip and falls, mountain biking mishaps, and the usual menagerie of human frailty and stupidity. While I worked full-time for only a few years, I’ve been a part of the EMS system in one form or another for over 25 years.

Thanks to its health monitoring features, the new Apple Watch Series 4 will save lives, probably within weeks of launch. I’ve been on real calls that might have had happier endings had the person been wearing one. I don’t know if wearing one would have saved that first victim—probably not—but Apple should get full credit for building a mainstream device that will save some lives.

That doesn’t mean it’s perfect. The Apple Watch Series 4 is far from a comprehensive life-saving device. It suffers from some serious limitations and faces some very real obstacles, especially cost and battery life, but in the end, some people will live longer because they wear one. Over time these features will become more reliable, more affordable, and more comprehensive, especially as Apple’s competitors catch up.

The Apple Watch Series 4’s three key health-related features are fall detection, atrial fibrillation detection, and a simplified electrocardiogram (ECG). Here’s how they might help, the limitations they face, and where Apple might go next.

Fall Detection

I responded to countless “slip and fall” calls over the years. These are one of the most common calls for paramedics. Particularly for the elderly, the consequences of a fall can be fatal even when there’s a quick response. Head injuries are frequent and serious, but hip fractures are even more common and can lead down a path from which it’s very difficult to recover.

You can purchase medical devices that monitor elderly family members while still giving them personal freedom. Anyone of a certain age remembers those “Help, I’ve fallen, and I can’t get up!” commercials. Typically, the patient needs to activate the device by pressing a button. Many of these devices are restricted to home use since they tie into a landline.

The Apple Watch Series 4 works similarly, detecting falls with its integrated accelerometer and gyroscope—see Joanna Stern’s Wall Street Journal video with a Hollywood stunt double for examples. It will then call for help if the wearer doesn’t respond to an alert within 1 minute. Since the Apple Watch knows when it’s on your wrist, there shouldn’t be any false alarms triggered by dropping it on your nightstand. It won’t detect all fall scenarios, and certainly not non-slip situations like slumping after a stroke, but the subset of what it can detect will likely rack up immediate saves. It can also work anywhere, not just in the home, like previous landline-tied solutions.

If you buy an Apple Watch Series 4 for a family member, make sure they wear it in the shower, when they’re most likely to have an accident. Yes, it’s sufficiently waterproof.

I’m not worried about there being too many false positives. First, it’s on by default only if the user has identified themselves as being over 65 in the Medical ID screen of the Health app; otherwise you turn it on in the Watch app. Second, there is a subset of falling patterns that is pretty distinct, and the combination of a fall, no movement for 1 minute, no response to an audible alert, and no response when 9-1-1 calls back should filter most of those out. False positives are a fact of the job, and EMTs deploy all the time on faulty fire alarms and injury-free car accidents. It bothered me only when I had just sat down to dinner.

Unfortunately, not every detected fall will result in a positive outcome. But it’s better to have someone respond right away than days later.

There are three significant inhibitors to the fall-detection feature. The first is cost, especially since all Apple Watches need an iPhone companion. That first inhibitor leads into the second, which is the complexity of both an iPhone and the Apple Watch in a demographic where the primary users may also be battling mental degradation. And this second issue ties to the third, which is the effort of keeping the Apple Watch charged and wearing it consistently. Again, this is likely a challenge for the most vulnerable population.

None of these is Apple’s fault; they’re just real-world limitations of the technology. The only thing Apple could change would be to remove the requirement that the Apple Watch be associated with an iPhone.

On the whole, I’m incredibly excited about this feature because it will save lives. Sometimes hyperbole is reality.

A Primer on Cardiology and Atrial Fibrillation

Before I discuss the next two features, it will help to understand the basics of how the human heart works. I’m oversimplifying intentionally—any cardiologists reading this article should skip this part to avoid increased blood pressure.

The heart has two halves and four chambers. The right side pumps blood to the lungs, and the left side serves the rest of the body. The top chambers on each side, the atria, are the “staging pumps” that load up the lower chambers, the ventricles, that do the real work. Without the atria, the ventricles can still move blood, but not as efficiently.

Heart cells are pretty wild and have something called automaticity. That means they can generate their own electrical signals and contract on their own without relying on nerve cells, as do most other muscles. Heart cells will beat on their own without external influence. They also work like a mesh network and influence the other cells around them. To keep everything coordinated, the heart has two pacemakers, bundles of cells that send out strong electrical signals so all the cells work together and squeeze when they are supposed to: the SA node (sinoatrial) in the atria, and the AV node (atrioventricular) for the ventricles.

The SA node fires and triggers the atria like the drummer in a band keeping time. This signal then shoots down special conductive pathways to the AV node, which sends a signal out and around the ventricles on different pathways to trigger the bigger contraction that moves the blood around the body.

Many things can mess up this process, and one of the more common is when something happens to the SA node, or the cells in the atria stop cooperating and get out of sync. That can lead to atrial fibrillation (AFib), where the cells of the atria stop working together and start contracting randomly. That causes the atria to stop pumping blood, leaving the ventricles on their own. While the ventricles can keep things moving by working harder—which also isn’t good—the worst issue is that blood can pool around and coagulate in the atria or the less-filled ventricles. This coagulated blood creates a clot, which the ventricles will happily shoot off to other parts of the body. If it blocks blood to the brain, that’s a stroke.

AFib can also cause weird effects like a dangerously high heart rate. Some of those random signals can, in turn, confuse the AV node, which is what causes the irregular beating of the ventricles, and thus an irregular pulse. If the ventricles beat too quickly, that becomes a medical emergency since your heart can only go so fast for so long. The high heart rate is also less efficient and further increases the chance of stroke.

Ventricles can also fibrillate. But if that happens, blood stops circulating, and you’ll die quickly. If you’re lucky, you get to wake up after someone yells “Clear!”

Detecting AFib with an Apple Watch

Apple worked with Stanford University on a study to refine the Apple Watch’s atrial fibrillation detection. AFib characteristically causes an irregular heart rate as those random signals hit the AV node or other parts of the ventricle. If the atria just stop working at all (it happens) or the random signals are blocked, those are different arrhythmia (electrical problems), and the AV node and ventricles will keep firing their signals at a regular, albeit inherently slower, rate.

All versions of the Apple Watch can detect your heart rate using special lights on the back of the watch that shine into the skin on your wrists. Other sensors detect subtle changes in the light coming back and measure differences in blood flow which directly correlate to your heartbeat. If this approach seems a little sketchy, it is—wrist-based heart rate monitors aren’t known for being highly accurate.

However, to detect atrial fibrillation, the exact pulse rate isn’t important. Instead, the Apple Watch looks for an irregular pulse, taking into account inherent noise due to the watch moving on the wrist or changing light conditions. If it detects a pattern of irregularity that matches AFib enough times, it alerts the wearer.

Atrial fibrillation is one of the most common cardiac issues, especially as we age, and a leading cause of stroke. Unless you go into rapid AFib (technically, AFib with rapid ventricular response), you might not know you ever have it. Early notification of asymptomatic AFib is a major deal since it is a manageable condition. Far more manageable than a stroke.

The Value of an ECG on the Wrist

Because the heart sends out strong, coordinated electrical signals, they can be detected fairly easily using an electrocardiogram, which produces a graph like the one below. The basics are easy to read. The first bump is the SA node firing—it’s called the P-wave. Then there’s a pause as the signal goes to the AV node, where you see a spike for the QRS complex, which shows the AV node firing and the signal triggering the ventricles to contract. The last bump is the T-wave, which shows the ventricles recharging to beat again.

My annotated ECG, taken using my iPhone and AliveCor’s Kardia device and app.

A traditional ECG measures all this activity with electrodes attached to your skin that detect those voltage changes. When I first started as a paramedic, we used 3-lead ECGs in the field, which let us detect only the most obvious arrhythmias. Attaching one lead on the right arm, another on the left, and one on the left leg creates something known as Einthoven’s Triangle and provides multiple views of how the signal moves around. These days we use 12-lead ECGs that offer a lot more angles and let us potentially detect things like heart attacks.

Einthoven’s Triangle, which shows the direction in which ECG leads read the heart’s electrical signal. Lead I, which the Apple Watch Series 4 uses, looks across the top while Lead II more closely follows the same vector as the heart.

The Apple Watch Series 4 includes a Lead I ECG, invoked by holding your finger on the Digital Crown. It gives a decent view of the heart, but Lead II’s data is usually cleaner since it captures a better angle that’s more aligned with the heart’s conduction path and thus shows the strongest signal. Given the inherent limitations of the Apple Watch’s sensors, or any single lead ECG, the Apple Watch Series 4 will only be able to detect basic arrhythmias and perhaps some interesting fitness data.

It should be possible to identify AFib because it shows up quite obviously on an ECG as a missing P-wave and a bunch of squiggly lines as the uncoordinated cells all fire on their own. Being able to identify AFib on demand will give doctors a much better view than the optical detection that sees only an irregular pulse.

However, a Lead I ECG can’t detect a heart attack. It can detect some other issues, but many of those require knowing things like the exact timing of the distance between the P-wave and the QRS complex. I suspect Apple won’t be providing warnings of such conditions anytime soon, since even experienced medical professionals can miss those issues, especially with only a single lead.

I think the most significant immediate value to the Apple Watch Series 4’s ECG capability will come in refining AFib detection and letting doctors better monitor known AFib patients. Over time, I’m sure more studies will look for additional issues that can be detected with the Apple Watch’s Lead I ECG, but they will always be limited to a few well-known and major arrhythmias that are both detectable and actionable. Ventricular fibrillation, for example, is easy to detect but you probably wouldn’t be capable of holding your finger on the Digital Crown because you’d be busy dying.

Nonetheless, I find the Apple Watch Series 4’s ECG promising. It will be of most value to physicians keeping track of patients with known issues, especially since the optical AFib detection is more likely to find a previously undiagnosed instance of AFib. Many AFib patients today have small sensors implanted into their chests to track their issue and call doctors if it gets worse, so clearly there is a medical need. It may also be useful in helping patients with heart conditions record ECGs during specific events and then share those ECGs with cardiologists—most heart events don’t take place in the doctor’s office. Over time I’ll be very interested to see if Apple can expand the technology to detect other arrhythmias, but I wouldn’t expect that anytime soon.

A New Healthcare Horizon

The Apple Watch Series 4 is a big deal. Fall detection will save lives nearly immediately. AFib detection will help reduce the rate of strokes. And the ECG feature will enable doctors to better monitor and communicate with their patients. Even young, healthy, active people will see benefits ranging from immediate help after crashing on a bike to early detection of congenital or random AFib.

Unfortunately, these features are available only to people with the financial means to afford an Apple Watch and iPhone, who are cognitively capable of using the devices, and who can wear the watch reliably and keep it charged. These are serious inhibitors for broad adoption among the most vulnerable populations.

However, none of this should detract from what Apple has done here. Even if the Apple Watch Series 4’s health-monitoring features are imperfect, even if they detect only a subset of issues and incidents, wearing one will allow some people to live longer and healthier lives.

Now that Apple has put its stake in the ground, I expect a few advancements moving forward.

First, it is likely that more insurance companies will start subsidizing or providing Apple Watches to customers. Some companies, like Aetna, John Hancock, and UnitedHealth Group, already do this to get people moving more with the health tracking. This should help reduce some of the financial overhead. Also, the price will go down over time as Apple introduces new versions of the Apple Watch and keeps older versions around at a reduced cost. It will also take a little time for physicians to hook into the ecosystem and start using its features with patients.

Regarding technology advancements, it’s best to look at the vital signs that we healthcare professionals always want: pulse, respiratory rate, oxygen saturation, blood pressure, and blood sugar (glucose) levels.

Apple has already nailed pulse. Respiratory rate can be detected electrically, but probably not on the wrist. There have been numerous rumors about solutions for the last three, and the latest devices from Garmin claim to be able to detect oxygen saturation. When combined with pulse detection, low oxygen saturation readings could help identify sleep apnea, which is another major indicator of long-term health issues. Like AFib detection, detecting sleep apnea has the potential for large quality of life improvements. I wouldn’t be surprised to see something along those lines within the next two revisions of the Apple Watch.

Blood pressure is also a key indicator of a wide range of health issues, especially stroke. Despite all the rumors, I haven’t seen enough science to indicate we are close to being able to detect it without inflatable cuffs. That’s a big tech problem that Apple is probably working on, but one that may not have a wrist-based solution.

The same goes for glucose levels, which are critical for managing diabetes. Right now, the only reliable measurement techniques require small blood samples. Accurate detection with a watch would be a massive scientific breakthrough with lasting social impact. But again, it’s not something we can predict.

Even without these additional features, the Apple Watch Series 4 encourages a more active lifestyle, can detect the early onset of a potentially debilitating heart disease, and can call for help during certain life-threatening accidents. These are huge advancements that will improve and extend lives. Even in my limited personal experience, I know of real-life incidents that might have had a far better outcome had the individuals involved worn Apple Watches. I’ll be buying some for certain family members this year, and even knowing the limitations of the device, I’ll sleep better for it.

Subscribe today so you don’t miss any TidBITS articles!

Every week you’ll get tech tips, in-depth reviews, and insightful news analysis for discerning Apple users. For over 33 years, we’ve published professional, member-supported tech journalism that makes you smarter.

Registration confirmation will be emailed to you.

This site is protected by reCAPTCHA. The Google Privacy Policy and Terms of Service apply.

Comments About I’m a Paramedic: Here’s How the Apple Watch Series 4 Will and Won’t Save Lives

Notable Replies

  1. Thank you for that concise and frank description.

    My understanding is that most of these functions are available on ealrlier watches (I have a series 3) and that Series 4 adds the basic ECG function.

  2. @ “… make sure they wear it in the shower, when they’re most likely to have an accident. Yes, it’s sufficiently waterproof.”

    I was in an Apple Store last weekend sitting at a table waiting my turn with an Apple Genius and overheard one of the Apple techs tell a customer he didn’t recommend showering with the watch on because soap, conditioner and shampoo used when showering deteriorates the watch seals and speaker membrane over time.

    In retrospect, I don’t know if the tech was talking about the new AW 4 or a previous generation.

    Does Apple have anything formally to say on the subject or was this just one tech’s opinion?

  3. I might argue, however, that if somebody is susceptible to a dangerous fall in the shower that taking the risk that soaps might damage the waterproofing may be worthwhile. Also, AppleCare+ covers up to two incidents of water damage like that with a reasonable deductible.

  4. Excellent points, Doug. And thanks for Apple’s link on the subject.

  5. I was knocked off my bike while mountain biking in France - went right over my handlebars. Ugly crash and the Apple watch 4 immediately recognized the crash and kicked into action. I was scraped but nothing serious, but I bought the watch for exactly this feature and it worked perfectly. I was able to stop the Emergency calls.

    Great that it works so well. Hopefully you won’t need to discover this like i did…

  6. As a family doc, I sometimes see patients who experience palpitations - an unusual sensation of feeling your heart beat. Separating those patients, for example, who “feel” their heart rate is beating rapidly from those who really do have a rapid rate is not always easy. Sometimes the patient doesn’t count the rate properly, can’t tell if it is regular, etc. If the Apple Watch could provide a reasonable single lead ECG (rhythm strip) for me to review, it would be very useful. The patient might be able to say “What do you think of this, doc?” on their first visit and enable me to accelerate the process of getting the right tests done more quickly.

  7. Apple is missing a logical expansion of their medical capabilities by not venturing into aiding hearing. They have earbuds, they have microphones and they have sophisticated electronics. Why not utilize them to capture nearby speech, filter it and transmit to the earbuds so one who is hearing impaired will be able to better understand?

  8. There is a Live Listen feature for the AirPods. I don’t know how much filtering it does.

  9. The fall detection for Apple Watch is nowhere near being accurate it will only get a lot of false readings,perfect example… The watch itself is triggered more by a solid impact from the accelerometer,case in point…, I could simply punch open a box, slam my hand hard on a table and it would trigger.I have even had on a couple of occasions had the watch off and had dropped it on the countertop,it would still register as a fall. The most disheartening was when I actually fell out of a tree putting Halloween decorations up three days ago, I fell 15 feet and the watch never registered the impact.Now whether this watch has an altimeter in it or not I have no idea but for it not to be able to register that I just droped 15 feet in 1 second regardless of how hard the impact was to the watch would be a main cause of concern .To be able to supposedly register a fall without just a simple hard impact it should also detect from what height you are at to what height the impact actually took place and this watch obviously does not do it.Four days prior to this incident I had taken the Watch over to the Apple Store to get it checked for poor battery life,the test came back clean.They also suggested that I re pair the watch (which I also did that same day)So obviously the watch is in perfect working order.

  10. It’s not actually that it deteriorates the membrane of the seal ,which eventually it would do regardless whether soap, chlorine, salt water… ECT but one of the main reasons they suggest that you don’t do that is that it will screw up the speakers with just all the extra soap film that would build up on them…Like when you have a lot of soap film on your shower walls and doors if you don’t clean it after a period of time

  11. That’s really interesting—everything I’ve heard has said that the Series 4 knows to enable fall detection only when you’re wearing the watch and when you trip or slip in certain ways. Joanna Stern’s video even showed some of the actions that didn’t trigger fall detection.

  12. I’ve seen a few anecdotal reports of false positive fall detections on reddit and a few forums that I follow. But I’ve also seen (I don’t have an S4 myself) that you get a warning when you turn on the feature that you may trigger false alerts from certain sports or if you are an active person. Fall detection is default only for people 65 and older, and I am thinking that only somebody in that age group, or who truly is susceptible to falls because of health issues, should have the feature turned on.

    By the way, a good post on the iMore forums by somebody whose wife had a false alarm, following up with some information from Apple support about how the fall detection feature works:

  13. That is not necessarily true, just because someone is over The age of 65 would benefit from this feature. I do electrical work and also work as a personal trainer “yes I know Polar opposite’s… LOL”. I’m on a ladder continuously and as well have taken my series of tumbles …happy to say nothing that serious. Anyone can benefit from having this feature, but I guess only the more active would benefit from this, if you’re a pencil pusher and sit behind a desk for most of your day and I can see why this would not be necessary for you.If they would just do further testing on it because obviously it’s nowhere near accurate.As for that article that you have sent a link to,unfortunately that’s pretty much common knowledge that anyone and their mother-in-law can look up on the Internet… We need the meat and potatoes version to find out how this exactly works and the tech support at Apple didn’t know their head from a hole in the ground, I spent at least a half hour with these people and they knew nothing short of what they were reading off the Internet.

  14. It is important to remember that the watch calls for help only if the person stops moving. In the case of a false positive the person is very likely to keep moving and there is no reason for the watch to send out an alarm. So I don’t think the false positives will create a problem, though we want as few false positives as possible.

    But every time you change things to remove a false positive you are risking introducing a false negative. This seems to be the story of anti-virus software.

  15. Anti virus soft wear???Ok… I’ll bite,what dose that have anything to do with it not picking up a fall?’s a matter of updating softwear to different specks and re training it.

  16. Yesterday evening my Apple Watch Series ‘detected’ a fall. At the time, I was sitting on my sofa, watching a TV show with my left (watch) arm resting on the top of the back of the sofa. No part of me had moved suddenly for several minutes. Anyway, I felt an unfamiliar vibration from the watch and looked at it to check it. I saw the 3 choices available and quickly selected the ‘I did not fall’ response.

  17. Maybe you were falling prey to ennui. :slight_smile:

  18. The Series 4 also provides the feature of fall detection, which was not available in the previous series.

  19. Great article! Thanks for the concise information. I did want to mention that as of Series 3, Apple watches no longer need to be tethered to an iPhone. That version of the watch does cost more than the gps only version and does require a monthly fee to a cellular provider, so there are still extra costs associated with the watch, but it may provide an option for some people who do not want to also have to buy an iPhone.

  20. I’m pretty sure you still need the paired iPhone to manage the Watch (update the OS, load apps, backup/restore). You just don’t need to carry the phone with you for as many tasks.

  21. Yes, that’s correct. An iPhone is necessary to set up and manage the Apple Watch.

    The interesting fact I learned recently is that a cellular Apple Watch can reportedly still call emergency services even if you don’t have a cell plan for it.

  22. Your comment about the watch calling emergency services resurrected a memory in regards to cell phones in general. A quick search revealed the following;

    Sometimes a defunct cell phone will still be able to call 911.

    In order for the phone to call 911, it has to have a working signal. It does not have to have a contract with a carrier (meaning you can’t call any other number and can’t receive calls). If you have a phone that will no longer be able to reach a working cell tower, either because you’ve moved to the Andes or because the phone company is discontinuing service, you won’t be able to reach 911 on that phone anymore. Other than the fact that 911 is available with or without a service contract on both mobile phones and landlines, there isn’t any significant difference between calls to 911 and other phone calls.

    Knowing that an old mobile phone will call 911 is important for a couple of reasons. First, if you couldn’t afford service and had to shut it off, you at least have a way to call 911 in a pinch. Second, knowing that they could accidentally call 911, you shouldn’t let kids play with old, working cell phones.

    I don’t know if this applies to countries with a different Emergency Response number but would be surprised if not.

    I found this on

  23. Hi, I have purchased an Apple Watch 4 for its heart rate function only, in Australia the heart rate monitoring function does not work. I get readings of 60 Bpm to 160 bpm within a few seconds. I also use a a ‘Kardia’ product which gives me an ecg over 30 seconds to my iphone or ipad which I have used to compare the apple watch 4 Hr function. Whilst the Ecg function is yet to made available at the moment Apple is falsely promoting the Apple Watch 4 in its ability to provide an actual real time accurate heart rate, I have had to resort to using a “Polar” chest strap with the Apple watch 4 to get accurate actual heart rates.
    Note I am in permanent AF my heart does not go below 100bpm

  24. Not sure why your location would make any difference, but here in Mountain View, California, mine has been spot on every time I’ve checked.


  25. Hi Al, I have checked the Apple watch 4s heart rate monitor against an old polar sports watch with chest strap as well as a ‘krardia’ device which gives an ECG over 30 seconds, the Apple watch has never been able to give a real time heart rate for me when compared to the other devices I’ve mentioned ( which I have verified when having ECG’s performed by my cardiologist . It is possible that when Apple make the ECG function on the Apple watch 4 available that it might give a more actual heart rate not a pulse. In addition Al I am in permanent Afib you might have a normal heart ie: when I sleep my HR is 11bpm to 160 bpm

  26. Sounds like you may have a bad unit. I’d recommend calling Apple Support or visiting an Apple Store and seeing if you can get a replacement.

Join the discussion in the TidBITS Discourse forum


Avatar for ace Avatar for stevemwerner Avatar for Felix01 Avatar for aforkosh Avatar for markwmsn Avatar for alvarnell Avatar for pchernoff Avatar for ecdm7k2jxv Avatar for ddmiller Avatar for mpainesyd Avatar for beachmail Avatar for rmogull Avatar for michaelcollins Avatar for Ronjohnstone Avatar for joe68 Avatar for Maria Avatar for Afib