FDA Data Confirm Smartphone Interference With Cardiac Devices - Page 1
Forum section: electronics / general

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: August 30, 2021, 08:00:49 pm
content: This is an article about smart phones possibly interfering in cardiac pacers. It says 10 G, which I take as Gauss, is enough to do something. That is pretty small since a frig magnet is several times stronger.https://www.medscape.com/viewarticle/957310?src=WNL_trdalrt_210830_MSCPEDIT&uac=356862FZ&impID=3603385&faf=1

author: TimFox
author_rank: Super Contributor
timestamp: August 30, 2021, 08:06:20 pm
content: From my days in MRI, I learned that a pacemaker was a contraindication for MR scanning, since they were designed to change mode (for medical diagnostic purposes) when a permanent magnet of a few gauss was placed on the patient’s chest. There were also horror stories about pacemakers in test “phantoms” (non biological) being tested in actual MR scanners and the resulting malfunctions (like absurdly high pulse rates).

author: SiliconWizard
author_rank: Super Contributor
timestamp: August 30, 2021, 09:24:09 pm
content: Of course, approaching any magnet strong enough would do the exact same thing. Like magnets on your fridge, for instance, yes.The alert here is that most people probably don't even know that smartphones embed magnets that can be strong enough for this, or that they embed magnets at all.

author: m98
author_rank: Frequent Contributor
timestamp: August 30, 2021, 10:23:46 pm
content: Seriously, what good reason is there for pacemakers to still use a reed-switch as an input device? With all the things you have to stay away from because they would either possibly trigger that reed-switch or otherwise disturb the device, how are they even passing regular EMI-tests?

author: TimFox
author_rank: Super Contributor
timestamp: August 30, 2021, 10:48:25 pm
content: Apparently, sometime around 2011 (after my work in MRI was over), pacemakers certified safe in MR scanners became available. There is, of course, the same problem with image artifacts as with other metal implants. Except for maglev trains, I’m not aware of other strong DC magnetic fields encountered by pacemaker patients.

author: SiliconWizard
author_rank: Super Contributor
timestamp: August 31, 2021, 02:19:40 am
content: Quote from: m98 on August 30, 2021, 10:23:46 pmBecause those are life-supporting devices and need to feature ultra-robust ways of activating them as required, sometimes in emergency situations. So that must be done using simple means, certainly not any fancy remote. A magnet is obviously something that can easily be found even if you don't have the tools from the manufacturer. There's of course the drawback that comes with it, but with proper care, since it's a very "short-range" effect, the overall benefit/risk balance is still in favor of those simple approaches. If it required any complex remote, you'd be screwed in case you didn't have access to any, or it was not working, or whatever.Some devices use Hall sensors instead of Reed ones. For the same function.Quote from: m98 on August 30, 2021, 10:23:46 pmEMI testing doesn't involve any static magnetic field AFAIK.Conversely, the sensors used for this task shouldn't be sensitive to the kind of testing routinely done for EMC.

author: m98
author_rank: Frequent Contributor
timestamp: August 31, 2021, 12:27:36 pm
content: Quote from: SiliconWizard on August 31, 2021, 02:19:40 amThere ought to besomebetter way. This is just lazy engineering.Magnets are easily at hand because strong permanent magnets (and strong low-frequency EM-fields) are everywhere. There is no reason for everyone to be able to change the mode of a pacemaker just willy-nilly. In ambulances and hospitals you already only have ring magnets from the manufacturers(which are also approved medical devices, nobody just carries some fridge magnets in the hope they might also work), those could easily be replaced by a standardized remote, that in its simplest form could function identically to the magnet by just having to place it on the device.

author: SiliconWizard
author_rank: Super Contributor
timestamp: August 31, 2021, 06:27:31 pm
content: Quote from: m98 on August 31, 2021, 12:27:36 pmSimple solutions that work and are robust is good engineering.Do not hesitate to suggest a better alternative. And then let it pass all analysis, use cases, reliability, regulatory compliance. We'll see how far you get. Probably thousands of engineers have already tried.Deactivating the devices, in particular for defibrillators (likely a lot more than for pacemakers), must be easy enough and you may have to do it in emergency situations.I have heard a lot of things, but that implantable devices are designed with lazy engineering, this is a first. So yeah, a bit of humility could help here. "There may be a better way, if we work hard enough on it, after considering ALL constraints and use cases." is probably more realistic than your statement above.

author: dferyance
author_rank: Regular Contributor
timestamp: August 31, 2021, 06:36:20 pm
content: As someone who mostly wears mechanical watches, I've been noticing how frequently magnets have shown up in everyday items. Magnets are very bad for mechanical watches. Normally, I'd expect to see them in motors, speakers and normal electro-mechanical devices but it is so easy to run across a random neodymium magnet used as a door latch or to hold a keyboard on a tablet or for charging cables.A magnetized watch isn't exactly the travesty of a pacemaker malfunctioning but I'd sure wish we didn't put magnets everywhere and used mechanical clasps instead.I remember those Microsoft Surface ads with the keyboard that clicks on and off. Hell no, keep those away!

author: m98
author_rank: Frequent Contributor
timestamp: August 31, 2021, 09:50:15 pm
content: Quote from: SiliconWizard on August 31, 2021, 06:27:31 pmIf the simple solution has the drawback of a critical device being way more vulnerable to external influence from common household items and appliances, then it certainly isn't a robust solution. I'd also doubt thousands of engineers have worked on this particular mechanism on pacemakers. It certainly is a legacy feature from a time where there really might've been no more reliable remote input mechanism than a reed switch so nobody ever dared changing that.Quote from: SiliconWizard on August 31, 2021, 06:27:31 pmAccidentally (and temporarily) disabling an ICD is also not nearly as critical as suddenly changing a pacemaker to asynchronous mode. One of both can make you require a defibrillator real quick if you're unlucky. I don't see how random people/first responders would benefit from triggering magnet mode on a patient with such an implanted device."Oh, he's screaming in pain, I haven't even recorded an ECG, I don't even know how to read an ECG (is that the thing with the wiggly lines?), but it must be his ICD malfunctioning! Quick, take off your magnetic belt buckle and let me fiddle it over his chest in the hope of being somewhere near the implant's location!" - Someone, somewhere, maybe.Quote from: SiliconWizard on August 31, 2021, 06:27:31 pmI was speaking in relative terms. Not using that better way that requires a lot of thought and hard work is "lazy". It's not like a corporation like Medtronic is on a tight budget, so there's no need to get overly protective.