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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'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
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...
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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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 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.
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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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"?