12 ms·
Real-time monitoring and continuous monitoring are different goals. The use case for something like this is probably a wearer who is experiencing heart palpitat
by ashwinsundar 1y ago
Real-time monitoring and continuous monitoring are different goals. The use case for something like this is probably a wearer who is experiencing heart palpitations, and has the time and clarity of thought to actually find the correct app on their device and start recording.
Continuous monitoring is extremely challenging still because ECG data needs to be sampled at a relatively high frequency (~200 Hz) to accurately identify the QRS complex in the waveform. That uses a lot of power, and the batteries we have still aren't good enough to support those types of demands. 200 * 60 * 60 = 720,000 samples per hour to collect and process.
It's possible that algorithmic approaches may be able to reduce the sampling frequency required. Power-constraints were the main issue when I studied this topic 10 years ago during my master's degree. I had looked into non-frequency domain techniques (such as empirical mode analysis/Hilbert-Huang transform) as a possible way to reduce sampling frequency and thus power consumption.
https://github.com/AshwinSundar/Empirical-Mode-Decomposition-for-MIT-BIH-Arrhythmia-Data/blob/master/Ashwin%20Sundar%20Final%20Report.pdf https://github.com/AshwinSundar/Empirical-Mode-Decomposition...
- sneak 1y agoi would imagine you could take an ekg for 1-2 seconds every 30 seconds and run it through a much more simple model to determine if it should take a longer sample, no? rather than reducing the frequency of the sampling, dynamically adjust the duty cycle of when sampling is happening? this is probably a dumb suggestion, it seems pretty obvious. for example the apple watch doesn’t do o2 monitoring continuously, just for some fraction of the time. do you need to sample every second to detect heart attacks? don’t they continue to show up on an ekg for more than 30 seconds?
- elric 1y ago> apple watch doesn’t do o2 monitoring continuously, just for some fraction of the time Making it effectively useless? Unless the fraction of the time is multiple times per minute? E.g. in sleep apnea it's not uncommon for some desaturation to occur, triggering an arousal and deeper breaths, restoring saturation, only for the cycle to repeat 2 minutes later. My Garmin has a similarly useless feature. I have no idea what the supposed benefit is. Maybe they hope that if they sample multiple nights they can detect some desaturation anyway and can get the user in for polysomnography? Might be worth it.
- jml78 1y agoI have mild sleep apnea and my Apple Watch is the reason I figured it out. If you wear it every night, you will catch it. I have on average 1-2 events an hour. Even with that few, the Apple Watch would catch the O2 drop enough times over a month that it worried me to see my O2 drop under 90%
- elric 1y agoImpressive that it caught it. Did the apple watch catch 1-2 events per hour? Or was that a sleep study? Sleep apnea isn't usually "officially" diagnosed until you hit >5/hour, 1-2/hour isn't even "mild", it's basically "normal".
- jml78 1y agoApple Watch just caught my blood oxygen dropping. I had a legit sleep study done. With my cpap, I normally have two 1-2 events/hour but my blood oxygen no longer drops
- firesteelrain 1y agoFitbit supports detection of Afib and has FDA approval. It’s not entirely out of the realm of possibility that one day it could also receive approval to detect heart attacks. It probably already has the data that might lead a savvy user to infer it just by looking at elevated resting heart rate, SpO2 differences, and irregular heart rhythm alerts.
- lazyasciiart 1y agoMy Fitbit record showing heart rate spikes to 125 was one of the things that I noticed that suggested I was having a heart attack in 2020 (I was).
- stavros 1y agoHm, why is 125 a heart attack? Isn't that a fairly normal heart rate for exertion? Or were you just at rest?
- firesteelrain 1y agoGP could have been having a non STEMI heart attack.
- lazyasciiart 1y agoI was, actually, but I don’t know how that’s connected? This was something like a ten minute spike in the middle of the night, a couple of times.
- firesteelrain 1y agoThe sympathetic nervous system activates, increasing heart rate and the body is trying to compensate for the compromised heart muscle. Then, there is the possible adrenaline surge because you are actually in pain. If the NSTEMI causes left ventricular dysfunction, the heart compensates with a faster rate to maintain blood flow. I went through this with a relative just two weeks ago and learned this from the cardiologists
- vlovich123 1y agoThere are audio recorders like TileRec by Attodigit that can record for 30 hours on a single charge and voice is recorded at 16khz and compressed live to mp3 and is super tiny at 0.5z. I’m thoroughly unconvinced that power or complexity of handling a 200hz signal is the bottleneck. 200hz is nothing probably even to a low end microcontroller these days.
- ashwinsundar 1y agoI hope this is true for ECG sampling as well! It does beg the question as to what is the bottleneck today then, if it's not power.
- hwillis 1y agoThis is out of my specific expertise, but the AFE1291 does 8k 24 bit samples per second and uses 495 μW when sampling. That's enough to run full rate for 10 straight days on an apple watch battery (1.189 Wh was the first google result). Integrated frontends have had big impacts on efficiency and improving batteries have had basically the same increase in specific energy. I would be shocked if power was a limiting factor. https://www.ti.com/lit/ds/symlink/ads1291.pdf?ts=1746971354934 https://www.ti.com/lit/ds/symlink/ads1291.pdf?ts=17469713549...