The 50-year quest to build a mechanical heart
theverge.com
theverge.com
For moral and regulatory reasons, these engineers cannot depend on large trial groups, the ability to rapidly iterate designs, run A/B trials, or exact much control over the quality and consistency of their sample subjects. And to top it all off, the nuances of human body systems are still very much 'black boxes' (in spite of our considerable and rapid advances in the field). From a business perspective, many of these efforts are viewed as nearly untouchable due to the levels of risk involved.
Yet, things like the artificial hearts mentioned in this article still manage to get developed. They're not perfect, but they're damn impressive.
I can only imagine the difficulty in building a device like an artificial heart. The fact that these artificial hearts work at all for any length of time is really a marvel of modern engineering and science.
Reality kicked in of course. It's always surprised me that an artificial heart is so difficult to perfect. The heart is probably the simplest organ in the body, yet the devil is in the details.
this is why it looks kind of yesterday to me (like many things in the other highly regulated industry - aviation - too) - why 100% requirement for one device? How about "horizontal scaling" - have 2 of them or 3 smaller and less reliable ones. Once one failed - that is a signal to promptly go in for the "service".
Replicating biology is a start, yet machinery has different advantages and disadvantages, so mechanical heart doesn't have to be a mechanical copy of the biological one. For example one can imagine having smaller helper pumps installed on all the big arteries, like near the groin for legs and near armpits for arms - that would improve the circulation and decrease the physical load on central arteries and overall energy consumption compare to the original biological schema of one central pump.
One is that if you're going to have three-way redundancy, then each one has to be one-third the size to still fit, which adds to the engineering challenge and may well make reliability worse.
Another is that not all failures can be fixed with redundancy. If one of your redundant hearts stops pumping, that's fine. But if it fails by, say, dumping all your blood into your chest cavity, then adding redundant hearts increases your chance of death, rather than decreasing it.
Since you mentioned airplanes, making sure redundancy reduces rather than increasing risk is a big issue. For example, single-engine airplanes are prone to crashes due to engine failure. The solution is to add a second engine and you're much safer, right? Except that twin-engine planes can be very challenging to fly with a dead engine, and if you're not very careful with design and training, you'll end up with an airplane with two engines that crashes if either engine fails, greatly increasing the probability of a failure rather than decreasing it.
that is the same thinking that has been in the aviation for the last 100 years. Why 2? Put 8 electrical ones driven from 2 generators from 2 ICE/turbines. In such approach no component have to be of an "air-worthy" level of reliability (and associated cost/price), just a regular "consumer auto" reliability level would easily do.
>But if it fails by, say, dumping all your blood into your chest cavity, then adding redundant hearts increases your chance of death, rather than decreasing it.
that is a good point. I'd say that abnormal flow can be detected, and with 2 hearts the option of shutting down the one where abnormal flow is detected is really a feasible option, while it is definitely not in the case of just one heart.
The thinking from the last 100 years of aviation has resulted in by far the safest means of transportation ever devised, with a fatality rate so low that it can no longer be reliably measured. Calling something "the same thinking" as that is high praise! If you think you have a better way to do it, it's certainly possible, but you have an extremely high bar to clear.
well, i did these calculations some years ago when i was looking at the cost of heavy low powered, ages in technology behind, engines like Lycoming. Cost of "horizontally scaled" solution is lower. Efficiency and reliability is higher. Weight for equivalent power may be a little bit larger, yet it is well balanced by the efficiency, ie. the lesser fuel consumption.
>The thinking from the last 100 years of aviation has resulted in by far the safest means of transportation ever devised
at the high level - definitely. But we aren't talking reliability of one huge heart for 200 patients - the cost here would allow to engineer 10 nines reliability. We're talking small individual devices. To compare - small aviation (included in the "General Aviation" below) is completely different - the GA is ~10 times more dangerous than driving :
http://www.meretrix.com/~harry/flying/notes/safetyvsdriving....
" For GA, there were 11.2 fatal accidents and 19.7 fatalities per million hours of flying.
For motor vehicles, there were 1.32 fatal accidents and 1.47 fatalities per 100M miles. "
and that after much more pilot training, after much more technical attention to the hardware and no 70+ year old "grannies" pilots :) . The technological state of small aviation, i.e. lack of technological progress for the last half a century at least, is bordering a shame of our civilization
I'm curious about your solution. How do you fit 8 electric motors to a GA aircraft? Where do they all go? Do they share props, or do they each have their own?
The most obvious way to place more props is the one which even NASA recently recognized benefits of (like increased lift) - http://www.nasa.gov/centers/armstrong/Features/leaptech.html . Yet that is just a start. Many props driven by smaller electric engines open a lot of other design possibilities - like easy tilting which easily brings us to VTOL - http://nextbigfuture.com/2014/08/nasa-research-shows-hybrid-.... Again NASA is very simplistic and primitive in their approach. The multi-wing designs along the Scaled Composites' ones may be more suitable here especially if cross-bred with typical octo-copter. The smaller props also open the possibility of ducts where is a bigger duct for one big prop is subject to very high loads and as result is very heavy and expensive and pretty much non-starter as a result. Ducting improves trust at low speed and decrease noise - both are big advantages for smaller planes.
I also don't see how this design makes VTOL easy. That design involves rotating the entire wing by 90 degrees to transition between horizontal and vertical flight. That's a huge complication over conventional aircraft where the wing structure is fixed. I can see how it might be a better approach if you already need VTOL, but if you're content with using a runway then using this design is going to massively complicate everything.
Finally, none of this appears to address the question of catastrophic failures versus benign ones. This design will greatly improve safety in the case where a motor just stops producing power. But for failure modes where, say, the motor catches fire or the prop comes apart, you've greatly increased the chances of a major problem.
not really - they are about of the same efficiency for the same power load.
> and you're putting virtually the entire wing in prop wash, which is going to screw up the airflow.
this is the idea here. Increased airflow for the wing means increased lift. Of course you need to make sure that it is good quality airflow. If you notice - the NASA uses kind of fans instead of props.
>I also don't see how this design makes VTOL easy. That design involves rotating the entire wing by 90 degrees to transition between horizontal and vertical flight.
rotating wing is just this NASA design and it isn't the best one. VTOL is a big theme. I'd just mention that [technically] successful VTOLs have been - CL-84, XV-15/V-22, X-22, XV-5 - and looking at them one can get an idea how a good number (4 minimum, 8 better) of well controlled prop+engine units would make for a good VTOL.
>But for failure modes where, say, the motor catches fire or the prop comes apart, you've greatly increased the chances of a major problem.
electric motor isn't an issue. A main generator unit - having at least 2 of them - can be easily immediately shutdown and flooded with fire-suppressor gas. Smaller props present less a danger and if in ducts that would be even less dangerous.
"This doesn’t only take from your body, it takes from your mind, spirit, and soul," De La Cruz says.
And:
Perhaps the biggest moral conundrum, though, has nothing to do with living with a mechanical heart, but dying with one. Unlike biological hearts, artificial ones can pump blood throughout the body and oxygen to the brain when the rest of the body breaks down. Death is dragged out — and may require the machine be shut off. "I’ve had patients where the liver and kidney failed, the skin turned yellow and died, and the only thing working normally was the brain," Arabia says.
I find stuff like this incredibly disturbing. I always find myself wondering why doctors don't spend more time on helping people keep their own organs functioning instead of on this kind of stuff. I find this very scary. "Resistance is futile. You will be assimilated."...because we are only going to offer you something Frankensteinian like this and not offer better options for healing the tissues you were born with.
I have a condition that accounts for a high percentage of lung transplants. So this stuff hits rather close to home for me.
They almost certainly do. It's a pure anecdote, of course, but I've had doctors in many states throughout the US and to a one, they communicate information intended to help me maintain better health as a preventative measure.
If you mean that doctors should spend effort on better treatments for failing organs, there are a number of projects working in those directions right now.
Basically, I'm not sure what is disturbing you.
I hesitated to reply to you at all. You kind of waved off my concerns and didn't really ask a question. So I am concerned that replying is a mistake. But I seem to be damned no matter what I do when it comes to topics like this. I mean, why did you reply? The manner in which you replied seems pretty dismissive, given that I closed with a statement that I have a condition where transplants are common.
But assuming you answered in good faith and just honestly don't see how bad your reply could sound to me, here is what disturbs me:
If you have certain conditions, doctors don't really try to help you maintain better health. They chalk up bad outcomes to your official diagnosis and kind of wash their hands of trying harder. Then heroic interventions, like transplants, get all kinds of glowing press.
When you get listed for transplant, you basically sit around waiting for someone relatively young and healthy to die tragically in an accident so you can have a second shot at life. I can't imagine the toll that takes on your psyche.
That isn't a criticism of patients who accept the only option they are really being offered. But I think we can do better than that, and real quality of life is being given short shrift as medical professionals zealously pursue the "Ooh, shiny!" options that will get them impressive headlines. I also understand the pressures on them which lead to that, but it is the patients who suffer horribly because of it.
It just makes me think something is very, very broken. And no one cares to even discuss that, much less try to fix it.
In any case, you answered my (assumed) question, so thank you!
So I began pursuing alternative treatments because doctors had no hope to give me. I did whatever reduced my pain, during a time when I was routinely hallucinating conversations with The Grim Reaper. And when I hallucinated that he peered down into my face, saw something he had not seen before and turned his black steed to leave, I ran screaming after him "Take me with you!" I knew the death watch was over and I would live. I also knew I faced a long, hard, torturous recovery. It was a journey I had no desire to make.
I think there are things worse than death. And I also very much fear two things: 1) That every minute put into researching heroics like artificial hearts is a minute taken away from researching something more humane and 2) the extremely high value we place on just making sure no one dies, and quality of life be damned, gives patients like me a very grim future, even if we get the best available care and do everything "right" (according to our doctors).
That answer is not intended as dramatics or as anything screechy. It is just honest commentary on my actual experiences that my views grow out of. Your question is a very reasonable one. I think my concerns are equally reasonable. I am aware few people will side with me on this. (Perhaps none, in fact.)
My grandmother when she was dying mentioned feeling annoyed that government would spend a few hundred a day on worthless treatments for old old lady on deaths door when kids were going hungry.
Sometimes, it is more humane to just let them die already.
Thank you for commenting.
My wife is an in home hospice care worker. She's seen people who have gone crazy from Alzheimers. They have these rare lucid moments where they understand what they're trapped in, and have begged her to kill them.
She's also worked with people who have Parkinsons, where their mental faculties are fine, yet their bodily control dissolves. They die by losing the ability to send the muscular commands to breathe. Suffocation.
So yes, when you talk about making durable organs to substitute failing ones, it sounds like a great idea. Until you hit end of life. At least ones where stuff fails isn't as bad, with all-mechanicals. The diseases that hit the brain and destroy cogent thought are the absolute worst. At least a family can potentially go to Oregon for physician assisted suicide.
Another solution to this is a kill switch: you hold the key to the destruction/End of Life of the device, killing you in the process. That would allow you to use these devices, and when you decide, to have a good death.
AFAIK, most of medical research is about "helping people keep their own organs functioning", by improving therapies, supportive treatments, and surgical interventions. (Of course, artificial replacements for one organ can also be a supportive treatment for keeping other original organs functional.)
> ...because we are only going to offer you something Frankensteinian like this and not offer better options for healing the tissues you were born with.
Generally, artificial replacements aren't offered where there are good, or even remotely viable, options for healing the tissues you were born with.
On top of all this, skeletal muscle tires quickly. A pump bulb arrangement might be better than a crank, but it's still the case that voluntary muscle movement isn't really designed for extended rhythmic use (eg: runners have to train a lot to be able to sustain running for any length of time)