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Living Without a Pulse
SteamyMobile writes "Can you live without a pulse? Yes, now you can. The reason why we have a pulse is because it's hard for evolution to result in turbines or continuously spinning things. The next generation of artificial hearts may have no pulse. They also have no bearings, so they should last much longer than previous attempts. In fact, engineers don't give a predicted lifespan on these models. How would your life be different without a pulse?"
I wouldn't be able to tell how hard I'm exercising. Which brings up the point that these turbines are going to have to be variable speed if they're going to accommodate humans' varying oxygen needs.
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I can't believe that the body has no problem with living without a pulse! I would have expected complicated side effects (the lack of rythm disturbing some other micro or macro cycles). Any biologists in the house care to explain how far back in evolutionary terms it is since we last had no pulse? Does nothing depend on it or do we really have the diversity in our dna to adapt to the situation?
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and what about love? would we feel the same without a pulse? (not that I know anything about it...)
I'm sure someone will be adding their favorite politician to this thread but seriously - I'd put money that there will be some consequences to not having a pulse. Valves will not get the exercise they need or something. N million years of evolution (or 7 days of design if that is what you buy into) means that there are probably lots of subtle interdepenancies of a pulsating blood supply. Of course some of the consequences might well be good...
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Considering our veins are outfitted with nice valves that prevent the backflow of blood in between pumps of the heart, what would happen to them when they are no longer needed? One would think that they just wouldn't close, which I suppose is fine, but it just seems that they might create an unwanted side-effect.
Also, it is possible that our organs aren't capabale of handling blood in a constant stream and they need those precious milliseconds of rest in between beats.
Perhaps I should've stayed in medicine and then I'd know these answers, but since I didn't, anyone know or have a better theoretical idea?
"Time is long and life is short, so begin to live while you still can." -EV
Well yeah, but this is for when natures's solution fails. Kidneys and bone marrow solve the blood cell damage problem. :-)
I'm wondering about the little one-way valves throughout the body which aid the pulse. Does such a system damage or suffocate those valves?
Aren't there other systems in the body which depend on the pulse? Could the move to a pulseless heart make a later transplant less likely to be successful?
When I took my freshmen chemistry courses in college, we had electronic stirs - you'd drop this plastic coated magnetic "plug" in a beaker, and then set the beaker on the machine. An alternating magnetic field would cause the plug to spin, stirring the fluid.
And now, 15 years later, someone finally figured out that you could apply the same principle to moving blood. Amazing.
I've always wondered why people bleed to death on the operating room table from trauma. When I worked as a mechanic, I had a supply of various diameter tubings readily available so I could plug a vacuum leak when diagnosing a carburetor malfunction. I've never understood why surgeons can't do the same with blood vessels - the patient is bleeding from a major artery, and it never occurs to them that the could slice the artery in half and connect the ends with surgical tubing?
I had always thought that there must be some really scientific reason for this, but now it occurs to me that it might just be ignorance. It took medical science 15 years to figure out that a lab stir would work better than bearings? I knew that as a freshmen! Ask the hubble designers - it uses frictionless magnetic bearings - maybe they could have clued someone in?
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The again, not having a working heart at all would probably undermine those mechanisms as well...
As someone who has worked with impeller pumps for the last decade, there is going to be a significant difference in the amount of damage done to the cells. I have seen live sea-life on the output side of impeller based pumps, where a propeller style pump does as you say, chop every thing up.
IIRC, blood vessels contain a number of one way valves which open and close in response to a pulse, so I'm surprised that these don't fail and have problems in the absence of one.
Maybe the pulse is not totally absent, from the article, this only replaces half of the heart, presumably leaving the other half to pulse along as before.....
I presume that they can't really pulse the pump to truly simulate a heart operation, as that may have effects on its power consumption and reliability.
On another subject, is blood affected by magnetic fields? I just wonder if any problems are caused by the magnetic coil drive system of this thing.
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Well, it would definately help tighten the groupings up at the shooting range. This could be a big boon to snipers :)
mdiarmspafpothama (My dad is a retired medical school professor and former president of the heart association midwest affiliate) and he agrees with you.
I told him about a woman in england that had an earlier version of one of these for several days while waiting for a real (human) heart (this was a few years ago). His imediate reaction was that pulsitile flow probably slows the build up of plaques in the arteries, and that people without a pulse would, IHNSHO (in his not so humble opinion), be more likely to experience blockages.
Of coarse that was just his gut reaction and he has not researched the topic...
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I'm sure someone needing a healthy heart would be glad to pay.
So... it appears we'll have to come up with a new way to measure blood pressure, particularly. Presumably, the best way to do this is to fit the turbine with inlet and discharge pressure sensors, and a flow meter. Step 2 is to establish some sort of numbers for what is "normal" for turbine heart patients.
This ups the ante for health care professionals by a bit. Not only do you need to know normal ranges, consequences, and treatments for standard BP and pulse ranges, you would need to be familiar with turbine pressure and flow ranges as well.
I think most paramedics would be clued in by the external battery and the power cord coming of the patients stomache that something about this patient was special. Also it's not as though people will be getting their hearts replaced with (well assisted by) these things willy-nilly they are only for people who have pretty much no other choice if they want to continue living. Also FTFA it will often be used as a temporary measure for people undergoing other treatment or who are waiting for transplants. The friends and family members of these people, the ones who might call the paramedics, will be well aware of the situation. In fact they'd probably call the cardiologist right after the paramedics in the event of an emergency who could relay special instructions. I also doubt this is a group of people that will be out in the wee hours of the morning bar hopping and getting falling down drunk.
So no this isn't a serious issue. It is, in fact, a non issue.
"Listen: We are here on Earth to fart around. Don't let anybody tell you any different!" - Kurt Vonnegut
Now their snipers won't have to worry about firing in between heartbeats. Anybody want to bet on how long it'll be before we have black-ops cyborg snipers with no pulse?
I saw this technology in a documentary on PBS at least fifteen years ago, but it was for a full heart replacement. They were reviewing artificial heart research after the Jarvik-7 was implanted. The odd thing was that the show went into a bit of detail about a centrifugal pump and its power supply, but I haven't seen anything about it since then.
Apparently a small nuclear pellet was used in the battery, which was in a lead-lined container about the size of half a D-size battery. The battery could be implanted completely, unlike the Jarvik, which requires a dangerous (susceptible to infection) tube running through the skin to a suitcase sized pneumatic pump. The issue they focused on was the danger of the radioactive pellet. Apparently concern had been raised about the possibility of an artificial heart recipient being in a plane crash. The fear was that the radioactive battery would leak. So they went to great pains to test it, including shooting it out of a gun, to show it was safe.
IIRC, the concept of being without a pulse, and the need for more research about this, was mentioned almost as an afterthought. But I've wondered ever since then what happened to this type of artificial heart. A completely self-contained apparatus would seem to be a godsend. But I always assumed that lack of pulse was the gotcha.
I even discovered that Marilyn Vos Savant, whose Q&A column appears each week in the national Parade insert to many Sunday newspapers. is married to Robert Jarvik, and consdered writing him in care of her about this device. But I never got a round tuit.
Xesdeeni
Did you know that many clocks depend on your outlet current being exactly 60 (or 50) Hz? In the US, I believe federal regulations dictate that over some specified period of time, your wall outlet has to count to the right total number of oscillations. When load is high, causing the generators to spin slowly, the cycle count can get off by minutes, and the electric company has to make up for in off-peak periods by running the generators faster.
In biological systems, we often see unusual dependencies. I think I read somewhere that certain birds can't swallow without gravity. And why not? It's there! Make use of it! That's the way evolution works. Nothing is more redundant than it needs to be (well, we can talk about transposons later). In humans, bone density is dependent on load, which is why our bones atrophe in weightlessness.
So, given that we HAVE a pulse, I would be surprised if some part of your body didn't take advantage of it.
I develped a pump for extracorporeal circulation of blood back in the mid 1970's and had to take a lot of these problems into account. My pump was pulsitile and had a very physiologic wave form including dichrotic notch. It also had 2 orders of magnitude less damage to red blood cells than the best pumps on the market at the time. (at least with the cow blood I experimented with) (Read on for an explanation of this) After spending a lot of money on patent lawyers, the device got shelved when I couldn't get a clear patent on it. I think people here on slashdot are missing the point of continuous (non-pulsitile) flow. The elasticity of the arteries especially the aorta actually adds to the pulsitile nature of blood flow. There is an artifact seen in blood pressure measurements called the dichrotic notch that is a direct result of this. If it is absent it is an indication that hardening of the arteries has taken place. The main purpose of circulation is to get blood to tissues and organs. Once there, it has to infiltrate the organs deeply in order to properly transfer oxygen and nutrients and carry away wastes. We were evolved with pulsitile flow and as a result the perfusion of organs and tissues is better with this type of fluid dynamic. That doesn't mean it won't work with constant flow, only that it won't be as efficient. It may take several years before these inefficencies result in some kind of problems. An increase in plaque deposition comes to mind because the tissues arent stretching and contracting. The other problem with turbines and impellers is the "waring blender effect" where the blood cells are "chopped up" by the spinning blades. This leads to hemolysis (release of hemoglobin into the blood form broken red blood cells) which puts a strain on the kidneys which aren't beilng perfused properly because of the non pulsitile flow, etc. etc. you get the picture. Anyway, it's interesting but not a permanent solution.
I remember seeing a documentary about this a few years ago and yes, the fact that prop/impellers chop stuff to bits was a big problem for the doctors working on the project. However, they used very sophisticated modelling and milling techniques (I think the term "developed for the space industry" was banded about) and managed to produce a design that didn't mulch the red blood cells.
A classic example of [potentailly] irreducible complexity is the bombardier beetle. It's a funky little critter that, when annoyed, shoots steam out its ass. The tricksy part is how it manufactures that steam without exploding.
The bombardier beetle has been used by creationists as an example of intelligent design, i.e., something this complex could not have evolved, but must have been created.
I fall on the evolution side of the fence, but, I have to admit, it's definately a thought exercise to imagine how this little dude developed his superpowers through evolution.
Creationist claptrap doesn't need to get peer reviewed to get published (and then subsequently spouted off on internet message boards). But since creationists like to talk about bacterial flagellums people have gone to the trouble to write peer reviewed published articles refuting the claptrap.
Is there some conspiracy of bible thumpers that come along and comment on slashdot biology threads and then up-moderate their co-horts or are there really enough fucking stupid slashdot readers that really think arguments like "irreducible complexity" have interesting merit?
If your heart is still contracting and it is not connected to the bloodstream, does it make a sound?
Thanks for posting that. Stuff like that is why I studied embryology, biomechanics, and evolution.
Unfortunately, this statement:
"While there may be circumstantial evidence to support either a continuous or discontinuous model of life, it is vitally important to recognize how one's starting assumptions affect one's conclusions."
is, in my opinion, typical of those made by people who have not studied biology but somehow can't come to grips with their beliefs being, um, wrong. There is no circumstantial evidence, or any other kind, for the discontinuous model. Sorry.
I admit I cannot draw you a picture of the stages in the evolution of flagella, but the more you study a variety of cellular phenomena you realize that there is only one possibility that is remotely self-consistent. Natural selection and evolution.
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Uh, isn't the entire point of these pumps to REPLACE the damaged heart? I mean if you have a low maintenance pump with little chance of failure why are you relying at all on the failing/failed natural heart?
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From the quoted article:
(3) Only one major system-level change of function, and four minor shifts of function, need be invoked to explain the origin of the flagellum; this involves five subsystem-level cooption events.
Only four minor shifts of function - all in the correct order, and only after all the requisite pieces have been evolved into place. Doesn't that sound statistically implausible? Doesn't that sound at all like constructing a remotely possible chain of events after the fact to fit the observed end state?
I call on Occam's Razor, and deduce that it's much more likely that the flagellum was created in place, rather than evolved through a bizarre sequence of highly improbable random events.
You are free to draw your own conclusions as to the nature of the creator.
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Irreducible complexity/intelligent design don't even pass muster under the most basic requirements of scientific inquiry and logic.
Affixing the word "theory" or "science" to them doesn't help. They predict nothing, they tell us nothing.
vk.
Perhaps you're right regarding contraceptives and tinkering with human systems, but the reproductive system is one system that can be tinkered with or even removed without too much harm to the rest of the body (re: castrations and all). Especially after puberty. I'm not sure if this is the best proof if you want to make a general argument.
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It's the end of my comment as I know it and I feel fine.
As someone who was born with a congenital heart defect, has had three surgeries, and has been ticking with an artificial valve for the last 22 year, I'd be worried about not having a pulse.
One of the things doctors/surgeons have noticed with heart patients that have their hearts stopped is that they lose all sense of time. I noticed it after my surgeries. I don't know if anyone has done research into the beating of the heart and the mechanisms in the brain that allow us to perceive the passage of time. Does the beat of the heart interact with the area(s) of the brain that perceive the passge of time? Do other bodily processes require a heartbeat for a "timeing signal"? I'm sure there are other questions to ask about this subject.
Show me a man with a song in his heart and I'll show you a man with an AM/FM pacemaker!
If "disco" means "I learn" in Latin, does "discothèque" mean "I learn technology"?
The process of organ donation is about as far removed from the eating a heart philosophically as it is physically.
In one case, you kill a man in an act of brutal violence, rip apart his chest, and eat the contents. The act is one of savage aggression, done not only out of the belief that life-force is absorbed, but also because the eating of another man is, in some respects, the ultimate form of degredation and dehumanization that you can subject him to.
I'd argue that the transplanting of organs can't really be construed as sucking the "life force" out of another so that one may live. Supposing that life force is indeed something real; surely, we can agree that it is not contained in the heart. If it is anywhere, it would have to be the brain. Whatever you think of the nature of our consciousness, you must agree that the brain inside our skulls is the physical container for it.
Organ donation isn't degrading to the donor or recipient. Whatever life force the former contained left him when his brain died. Perhaps you feel that it is degrading to consider ourselves as a collection of biological parts, like a machine, but with what we know today, this is demonstrably so. Further, I simply can't see why this could be construed as degrading: we are what we are.
I'm rather curious as to how you perceive the body and mind... I suppose I see them as two completely separate things, interconnected to the degree that the former must support the latter... do you feel that they are one in a sense that biology does not fully explain, and that playing mix-and-match with parts of the body does something to upset this? If so, would you argue that recipients of donated organs are made less human in the process, or are somehow degraded?
I'm quite curious as to your opinions, because you're the first person who has voiced an objection to organ donation based on something other than religious belief, distrust of the medical profession, or vaguely described discomfort with the idea. I look forward to a reply.