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Nuclear-Powered Cardiac Pacemakers
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Re: Nuclear-Powered Cardiac Pacemakers
#92Tragically relevant story to accompany this article: the Goiânia accident. https://en.wikipedia.org/wiki/Goi%C3%A2nia_accident
It's the scary goldilocks of nuclear waste. On the one extreme, you have the Elephant Foot at Chernobyl, which even today will kill you if you, like, go up and lick it. But it's not going to sneak up behind you, so just don't go over there. On the other extreme you have the release of radioactive water from Fukushima, which instantly dilutes to nothing in the vastness of the ocean. Meh. In the middle, you have radiat…
There’s another scary Goldilocks aspect too, which is what I thought your comment was going to be about when I started reading it.
Stuff with a really short half life is horribly radioactive, but not for long. Stuff with a half life of millions of years sticks around forever, but it’s not throwing off that much radiation. But stuff in the middle (a half life of perhaps decades to a thousand years) can be very dangerous and remain that way for a long time.
Re: Nuclear-Powered Cardiac Pacemakers
#93Earlier quoted context omitted.
Just because you pay a positive non-zero amount for less than a quarter of the energy in, it does not mean that a device has greater than 100% efficiency, which is not possible. If heat pumps are 400% efficient then log burners in cabins in the woods are even better.
A heat pump warms a home more efficiently than using the same amount of electricity for resistive heating. It can do this because it's not generating the heat from scratch; it's moving heat from outside to inside. https://en.wikipedia.org/wiki/Heat_pump#Performance
I know. It's only >100% 'efficient' if you ignore the input of 'outside heat'. That is not a normal calculation, and not really called 'efficiency'.
It's desirable for multiple reasons, of course, but it's not efficiency.
Re: Nuclear-Powered Cardiac Pacemakers
#94Wonder how I slided into the world of Fallout? WTF!?! We have plutonium powered pacemakers? http://large.stanford.edu/courses/2015/ph241/degraw2/ Ah, okay we had . > Despite the often longer life-expectancies, nuclear pacemakers quickly became a part of the past when lithium batteries were developed. Not only did the technology improve, allowing for lighter, smaller, and programmable pacemakers, but doctors began to…
> allowing for doctors to check in on their patients and replace either the batteries or the pacemakers themselves I cynically read this as "we needed to get more money out of these patients"
>longevity of nuclear pacemakers was excessive
Same. In what world can a lifesaving device run excessively long? One with our health system is where...
Re: Nuclear-Powered Cardiac Pacemakers
#95Earlier quoted context omitted.
You really should not. 60 beats per minute means that in ten years the leads of a pacemaker will be bent *315 million* times. That's an order of magnitude higher than we typically test fatigue resistance, and even if we were that confident about being able to produce flawless materials, there are millions of different enzymes and acids and temperature fluctuations in the body. Any one of those could impact the fatigu…
> 315 million times. That's an order of magnitude higher than we typically test fatigue resistance Nah, it's not that bad. Decent mechanical keyboard switch is specified for 100 million clicks [1, or google for "switch million actuations"]. Surely good engineering can eek out another order of magnitude. Not to mention - pacemaker leads ("wires"), the only part that bends, have way less stress on them (= larger bend r…
I've had Cherry switches fail right as the keyboard's warranty was up. The switch feels soft after wearing out, it gets dust in it and starts double typing, etc. Pacemakers need to be 100% reliable, not 99.9%.
Re: Nuclear-Powered Cardiac Pacemakers
#96Earlier quoted context omitted.
Just because you pay a positive non-zero amount for less than a quarter of the energy in, it does not mean that a device has greater than 100% efficiency, which is not possible. If heat pumps are 400% efficient then log burners in cabins in the woods are even better.
All energy from log burners comes from the fuel, and some ashes remain unburnt. They're under 100% efficient at converting fuel to heat. You put in x fuel and A heat pump takes heat from outside the system. You put in x fuel and you get >x heat. Getting more energy than you put in makes the efficiency over 100%.
I know. You can't just ignore the bulk of the input and still call it 'efficiency' though.
Even manufacturers call this 'coefficient of performance', not efficiency.
Re: Nuclear-Powered Cardiac Pacemakers
#97Earlier quoted context omitted.
You really should not. 60 beats per minute means that in ten years the leads of a pacemaker will be bent *315 million* times. That's an order of magnitude higher than we typically test fatigue resistance, and even if we were that confident about being able to produce flawless materials, there are millions of different enzymes and acids and temperature fluctuations in the body. Any one of those could impact the fatigu…
> 315 million times. That's an order of magnitude higher than we typically test fatigue resistance Nah, it's not that bad. Decent mechanical keyboard switch is specified for 100 million clicks [1, or google for "switch million actuations"]. Surely good engineering can eek out another order of magnitude. Not to mention - pacemaker leads ("wires"), the only part that bends, have way less stress on them (= larger bend r…
Seen way too many failed Cherry MX (OG, vintage and third-party) switches to believe that.
Re: Nuclear-Powered Cardiac Pacemakers
#98Earlier quoted context omitted.
> allowing for doctors to check in on their patients and replace either the batteries or the pacemakers themselves I cynically read this as "we needed to get more money out of these patients"
You really should not. 60 beats per minute means that in ten years the leads of a pacemaker will be bent *315 million* times. That's an order of magnitude higher than we typically test fatigue resistance, and even if we were that confident about being able to produce flawless materials, there are millions of different enzymes and acids and temperature fluctuations in the body. Any one of those could impact the fatigu…
It sounds like you have quite a bit of knowledge on the subject. I had to get a pacemaker a couple years ago, and am an embedded engineer. I hope to live another 50 years at least, so this is an interesting subject for me.
Maybe my cardiologist is just trying to make me feel good, but he says my leads will likely last 30-50 years. Intuitively that seems unlikely, but we'll see. It's got to be one of the most engineered cables in existence.
The leadless pacemakers are indeed a technical marvel, but they aren't yet nearly as feature packed as shoulder implanted devices. They'll keep your heart from stopping if your nerves are flaky from time to time, but they don't have the energy storage to do much more than that. Mine monitors every single beat my heart takes, and automatically reports issues to my doctor via BLE. (Is bluetooth more or less scary than radioactive isotopes mounted in your body?)
For about 8 months, my AV nerves were completely broken, and the pacemaker paced my ventricles 100% of the time. It was a nearly perfect drop-in replacement for the failed nerves. A leadless pacemaker wouldn't have had nearly the same performance. My nerves eventually started mostly working again, and now I'm on track to have a battery life pushing 15 years.
It would of course be great for the technology to advance even more over the next decade. Since my nerves mostly healed, a leadless device with a 30+ year battery life would be a nice replacement. With a shorter battery life, I don't really want to be collecting them in my heart (they don't plan to remove leadless pacemakers when they die.) I'm hoping by the time my current device is worn out, it will have logged enough telemetry for me to convince my cardiologist that I don't need a pacemaker at all, though.
Re: Nuclear-Powered Cardiac Pacemakers
#99Wonder how I slided into the world of Fallout? WTF!?! We have plutonium powered pacemakers? http://large.stanford.edu/courses/2015/ph241/degraw2/ Ah, okay we had . > Despite the often longer life-expectancies, nuclear pacemakers quickly became a part of the past when lithium batteries were developed. Not only did the technology improve, allowing for lighter, smaller, and programmable pacemakers, but doctors began to…
> Due to the extremely high risk and toxicity involved with using plutonium, numerous layers and shields were woven into these pacemakers resulting in larger and heavier devices. Despite strong concern of radiation exposure, the actual risk of exposure from these plutonium-powered pacemakers was almost non-existent.
What a strange phrase. I would say it was because of the concern of the risk of radiation, not "despite" it, leading to the precautions built into the device, that the risk was reduced to "almost non-existent".
Or is this a claim that the shielding was unnecessary?
Re: Nuclear-Powered Cardiac Pacemakers
#100Earlier quoted context omitted.
You really should not. 60 beats per minute means that in ten years the leads of a pacemaker will be bent *315 million* times. That's an order of magnitude higher than we typically test fatigue resistance, and even if we were that confident about being able to produce flawless materials, there are millions of different enzymes and acids and temperature fluctuations in the body. Any one of those could impact the fatigu…
> 315 million times. That's an order of magnitude higher than we typically test fatigue resistance Nah, it's not that bad. Decent mechanical keyboard switch is specified for 100 million clicks [1, or google for "switch million actuations"]. Surely good engineering can eek out another order of magnitude. Not to mention - pacemaker leads ("wires"), the only part that bends, have way less stress on them (= larger bend r…
The absolutely arrogance to assume a keyboard switch and a pace maker are anywhere near the same thing…