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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?"
... waking up in a coffin because someone thought you were dead :(
I hate sigs
I wouldn't have to take the two different high-blood pressure meds that I do now. That would save me about $35/month and the random side effects that go with taking these medicines (shortness of breath when exercising, dizziness when getting up to fast, etc).
I heard that people without pulse get a sense of disorientation and un-equilibrium. Especially those with screw drive hearts. Since the body has operated on a pulse for so many years, I have talked to people that have these screw drive heart devices, and they initially they couldn't even sleep at night because they didn't have the pulse in their ear.
There are certain advantages to having a "pulse". Examples are: The alternating low and high pressures may allow the bodies baroreceptors to better control blood pressure and there are other important feedback mechanisms associated with having alternating high and low pressures in response to the heart contracting. I would worry that some of the new pumps could undermine those mechanisms.....
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I wonder what kind of effect this has on the body. Think about it, it's a pretty constant stream of blood flowing, as opposed to a stop/start of a pulse. Sure, there's several (I'd say at least... 5 or 6)* pulses per minute, but if I remember seeing video of a cellular level for vessels, it looked more like a semi-congested LA highway rather than a smooth flow. My guess is you'd probably need some sort of batteryless implant that would measure blood pressure as well.
* Very technical here.
Small potatoes make the steak look bigger.
A few months back I did a first-aid course at work. One of the interesting things I found out was the technique they use for checking to see if someone's heart is beating:
Basically, you pinch their earlobe. This forces the blood out of the lobe, and then you let go. If colour returns to the lobe, then the heart is beating and blood has been pumped back in. If it does not then blood is no longer moving around the body.
This technique would probably also work for those with no pulse.
I had a very similar reaction, IANAHS (I am not a Heart Surgeon) but in the article it says...
it only has one moving part, a spinning impeller that drives a continuous stream of blood.
Surely the human body is not designed for a continuous stream of blood ?.
Saying that I am sure that this has all been researched thorougly to get to this stage and my limited medical knowledge probably isn't very useful.
You are absolutely correct. If you look at the internal surface of a major vein you will notice that it it is uneven. It does not allow blood to flow back and this works properly only with a pulse flow. It will not work properly with a constant flow. So people who rely entirely on a device like this will be prone to various vein problems - varicose veins, cirrose like vena portalis deformities, etc. So devices like this cannot replace a heart 100%. At the same time they may be enough to provide assistance for a week or failing heart (this is what these guys are claiming to do anyway).
While on the subject, continuous exposure of blood to a strong magnetic field is not something that has been investigated and there may be some long term problems associated with it.
Baker's Law: Misery no longer loves company. Nowadays it insists on it
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Lol. As a former nuclear/plasma physics graduate student, it makes me laugh even more. Do you know how that caterpiller drive actually works? The field of study is called magnetohydrodynamics and is one of the most @*#%$!* involved things I've studied...
Basically, you have an electric field of some sort or readily available ions (think, salts in the ocean water), apply some strong magnetic fields of differing strength, and cause a forceful ion drift in the direction perpendicular. I just call it Evil Fluid Dynamics With 50 Other Variables.
As an aside, since there are relatively fewer dissolved salts, the Red October's caterpiller drive wouldn't work in fresh water. Neat eh? Not that there are terribly many huge bodies of fresh water where you'd worry about silent submaries.
At any rate, there are dissolved salts in blood, aren't there? So you could theoretically do this for a heart pump. But who knows what the heck it'd do to the patient and I'm guessing you'd need a whole lot of auxiliary equipment.
A preposition is a terrible thing to end a sentence with.
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?
Also, the heart isn't the only pump in the body - the muscles in your legs help return blood to the heart when you run. That why if you run then stop abruptly you feel faint, because suddenly the load on your heart has suddenly increased and it needs to ramp up to pump blood all the way up to your head at a usable pressure (which is one reason you should warm down properly after exercising). How would the impeller interact with "pulses" from the legs?
Actually, I just took the CPR course recently, and they specifically left out 'taking the persons pulse' and told us to rely on watching for signs of movement in the chest, and looking for breathing.
Apparently many people are very poor at checking for a pulse, and it was unreliable.
"Ignorance more frequently begets confidence than does knowledge"
- Charles Darwin
Actually, I read a Reader's Digest article about a similar pump a couple years ago. Some young girl in England had a viral heart infection and would have required a transplant. Instead, they stopped her heartbeat and implanted a constant pump like this. The doctors were all concerned about the effects of not having a pulse, not having 2 bounces for blood pressure measurements.
She lived quite well with the device and the stopping of her heart actually let the heart muscle repair itself. It turned out that resting the muscle was very good for it. She was eventually taken off the device and her heart restarted.
So no, there are not the adverse effects doctors had theorized about.
Do really dense people warp space more than others?
This is something I know about, I am an engineer and work with centrifugal pumps (engineering classification of these impeller/turbine pumps. You can make them variable speed and use the speed of the impeller to control the flow of the medium being pumped. There are many advantages to this, but it is not the common flow control scheme. Most of the time, the speed of the impeller is held constant and a control valve on the discharge side of the pump is opened and closed. As the discharge vale is open, flow goes up, as the valve is closed, the flow goes down. I woudl venture to guess, that the muscles that apply pressure to arteries to direct the blood flow (an everyday normal activity in all human beigns) acts as the flow control and the pump just sits at normal speed. If you have a variable speed pump, they would have to tap into the nervous system to determine the blood needs of various organs/tissues and use that as speed control, not going to happen, or give you a rheostat on your side that you coudl turn up and down the spped of the impeller based on what you were doing (sarcasm). Summary, constant speed centrifigal pump with the flow control being down by the discharge valve (this case muscles on the arteries that are already there) and the pump impeller speed never changes.
...most CPR certified professionals check for breathing, not a pulse.
Ah yes, but next will be the 2cm artificial lung that doesn't inhale and exhale. More like an air filter for oxygen than a lung, I guess.On the other hand, once cyborgs are that advanced they'll have digital readouts for their vital signs, right? Or flashing green LED's like a network card on the back of your neck.
Anyway, if the lights are flashing when they talk, and that plunger is still flapping up and down, then that dalek is still alive, Doctor.
- Now, let's say that they determine that the guy with one of these hearts dies. If the heart just continues to operate, things could get
- messy when he gets to the morgue! And the mortician may have some psychological problems after cutting open a dead person have having blood flow out of its body instead of just leak out since the artifical heart is still operating.
Before I go any further, I'll stop.I have a bumber sticker in my cubicle that says
I wouldn't know; In high school, my BP tended in the uncomfortably low 80/50 range... which caused at least one school nurse much consternation, as she couldn't find my pulse in wrist or throat. "Dear, are you sure you're breathing?" Since getting out from my mother's obsessively healthy "low salt/low fat" cooking, I've achieved a more normal 100/70 normal BP.... but I still don't hear my heartbeat.
//Information does not want to be free; it wants to breed.
I'm no medical proffessional, but isn't blood pressure measured by listening for the pulse while constricting the flow with a sphygmometer.
How would blood pressure be measured without this reference. Like air pressure in tires?
Thanks to the internet, we can now all die alone together! -SomeWoman
Well, having actually spent some time doing partial and total artificial heart research, including about 6 years with the earlier LVAD (pulsatile) technology, I'm of two minds about this.
1. I don't believe we'll see increased atherosclerotic plaque deposition due to non-pulsatile flow. I'm currently subscribing to the theory that plaque is related in chronic bacterial infection of the vascular intima.
2. There was some evidence, but poorly followud up in the past, that renal function was on the short list of critical elements requiring pulsatile flow. One reason for inadequate continuing studies was that the problems with on-pump anticoagulation, infection and anesthesia tended to introduce enough variables to make isolation of the pulse issue too obscure.
3. There have been a number of reports in the past, some as long as 15 years ago, of surgeons using the Biomedicus BioPump, a similar design, for extracorporeal bridging support to transplantation, or similar to the anecdote below, to place the heart at rest to allow its recovery. I'm aware of many cases (I participated in at least 10) of multiple-day attempts, and at least 2 or 3 trials of several weeks. Realize that the patients were already moribund, so supporting them in bridging, awaiting a suitable donor, was their last and sole chance for survival. And, no, most of them didn't survive to transplant.
I'm intrigued. I'm out of the business now, but I'm convinced that we're overdue for some real breakthrough to make implantable artificial devices for continuous perfusion a viable alternative to transplantation with the limited pool of donors.
Never ascribe to malice that which can adequately be explained by tenure.
When you place the heart at rest, you remove the load it sees, and use an artificial pump to do the work.
You don't stop the heart. Even today, with cardioplegic solutions significantly advanced, supplemented with NAD-compounds and amino acids, stopping the heart bears the significant risk that you can't get it restarted again.
Cardioplegia for cardiac surgery involves infusing a potassium-rich solution into the coronary arteries, which stops the heart in diastole. Further, the solution is cold, and the heart is bathed in an iced saline slush to cool it further and diminish its metabolic requirements. At this point, the heart is *NOT* getting a blood rich perfusion (barring the use of blood-based cadioplegia, which I'm still not sure is as good an idea as some others think) medium.
If you were to start reperfusing the arrested heart with blood, with a normal electrolyte composition, the extra potassium would be washed out, the heart would rewarm, and if it has sufficient energy stores, and a sufficiently normal physiology, it would begin to contract again.
So: To put the heart at rest, you unload it, keep the blood chemistry as normal as possible, maintain good nutrition status (parenteral alementation), and see if the heart muscle recovers.
Never ascribe to malice that which can adequately be explained by tenure.
But if you're breathing, it's safe to assume that your heart is working. That's basic physiology. And not quite true. I've had several patients without a pulse continue talking to me for a while. Looking over at the monitor revealed non-pulse producing rhythms to go along with the lack of pulse. Eventually, everyone went back to following standard physiology - one way or another. But those transients are memorable. (It's worth noting that there's a standard pre-hospital med that would cause asystole (flat line) for about 30 sec. The patient would report "feeling funny." The only problem was that patients would get upset when they'd see the heart monitor go flatline. There was a simple solution to this - we put the monitor where the patient couldn't see it.) Rob
This sig seemed like a good idea at the time....
"The problem is no-one's going to check your wallet for a consent card for CPR, so she's had her chest tatooed with a warning saying something like "Get thos f*cking this away from my f*cking chest. If you revive me I'll sue your arse off!". "
Kind of remindes me of my EMT instructor, She has three tattoos
There is an "X" two fingers above her zyphoid process (where you put your hand for chest compressions)
and underneath is says push here.
She has the outline of two fingers on her right wrist.
And a circle around her vein in her arm.
Lets just say that if she didn't train them she doesn't trust them.
Then again she is of the opinion that no matter how far along a woman is in labor when you pick them up in an ambulance if the baby is not born in a hospital your driver is to slow.
While I mostly agree with you, I have one nit-pick/addition. As a former meat wagon operator (oh, sorry...I mean paramedic), checking for blood flow in extremities can be done by checking capillary refill as well.
Huh? Yeah...push on your fingernail. The nailbed turns white. The time it takes to go back to pink/red is your capillary refill time. Should be 1-2 seconds max, or you've got problems....not necessarily low bp....dehydration and low o2 saturation will do it too.
That being said, no pulse....how the hell do I get a BP? I'm guessing my pulseox won't work either. Do they have an LCD control panel mounted on their chest so I can check and adjust their BP with a little screwdriver? I can see this type of thing really compilcating/confusing emergency medicine.
Do not fold, spindle or mutilate.
I noticed that the pump still has external wires for power. I thought it was generally believed that this was a bad idea, because the holes in the skin where the wires come out is a prime place for infections and such. I thought the `state of the art' was to have rechargable batteries inside, and charge them via an electromaget placed outside (basically it's a transformer.)
Bombardier beetles are awesome... I remember reading about them in a chemistry textbook - I always wanted to see one in action.
From another site:
The bombardier beetle lives in South America and relies on the enzyme catalysed decomposition of hydrogen peroxide to defend itself against predators.
The beetle has a gland on the tip of its abdomen that contains two chambers. One chamber contains a mixture of hydroquinone and hydrogen peroxide and the other contains a mixture of two enzymes, catalase and peroxidase. When the beetle is threatened it mixes the contents of the two chambers. The enzymes catalyse the decomposition of hydroquinone and of hydrogen peroxide. Both of these reactions are exothermic so the mixture gets hot. The oxygen from the decomposition of the hydrogen peroxide builds up a pressure that is used by the beetle to spray its attacker with a stream of hot, corrosive liquid.
I never thought about that being an irredudibly complex system... but I see the wiki article you linked to even mentions the possibility.
..He could not get his sleep rhythms right for about a year, which the doctor who operated on him said was common, so no pulse may mess up your sleep cycles.
This was when they used a blood circulation device when his heart had to be worked on
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You said: Can anyone offer a plausible explanation for how any one of the pieces of a bacterial flagellum would offer that bacterium some sort of advantage?
Why yes, I think we can!
A nice quote from the conclusion: ...the very fact that a step-by-step Darwinian model can be constructed that is plausible and testable significantly weakens the suggestion that extraordinary explanations might be required.
Nice try though...
A major problem with continous flow would seem to be the diastolic part of the cardiac cycle (when the heart is refilling) is critical for back-flow from the body (arteries do not have valves) into the coronary artieres (the arteries that feed the heart). The aorta (main artery from the heart to the body) is elastic, so a large bolus (fluid surge) of blood is ejected into the aorta, stretching the aorta during systole (contraction of the heart). When the heart then relaxes (diastole) the stretched aorta recoils, and squeezes blood both forward and backwards. The heart has an output check valve at the aorta (aortic valve) which prevents it from completely flowing back; however a small takeoff (the sinus of valsalva) allows the blood to surge into the coronary arteries, and since the heart is relaxed, flow all the way to the muscle of the heart. I don't know if someone has looked into coronary blood flow during these continous pumps, but it might be useful to see, since these hearts are in bad enough shape without becoming ischemic (oxygen starved)
Presumably, after indulging in an experimental and no doubt expensive procedure, I'm betting that the subject would be given a MedicAlert bracelet that would give the attending EMT a head's up...
"I'm a scientist! I don't think, I observe!" - Dr. Clayton Forrester
I'd appreciate a link to that... I've been doing this for a long time, and I've never thought that belief was widely held. I've heard of theoretical links between C. pneumoniae, but that's about it (of course, C. pneumoniae has been theoretically linked to all kinds of things, including Chronic Fatigue Syndrome, among others).
I'd say the classical risk factors for heart disease still hold; smoking, hypertension, diabetes, the bad gene (usually a triglyceride or cholesterol metabolism problem), etc. This really isn't a flat-earth-round-earth debate... Any new theory had better be pretty compelling, particularly with the mountain of research backing up the standard risk factors.
The "bacterial infection" guys may turn out to be right... but they're going to have to prove it.
Even if a man chops off your hand with a sword, you still have two nice, sharp bones to stick in his eyes.
Blood will always flow if there's pressure behind it (doh). I'd expect, based more on physics than any experience in cardiology, that a continuous flow at maybe 100mm (well below common systole) would work just fine without overstressing any part of the system.
But if future studies were to show that a pulsing system really does something useful, it shouldn't be too hard to put a controller chip that has the impeller spin up and spin down at some reasonable rate.
BTW, just because it's different from nature doesn't mean it's harmful. For example, it may have taken 50 years (largely due to politics) but it's now considered medically safe for women to take continuous contraceptives and go without menstrual cycles for all or most of the year.
https://app.box.com/WitthoftResume Code: https://github.com/cellocgw
I recall an old science show that said that the pulsating pressure was actually important for the human body. As I recall (and it's been nearly 20 years), the pulse helps the blood travel down certain pathways it couldn't reach under a steady push, and that it gives the body more time to transfer the goods, so to speak, intra-pulse. The discovery was made because the old dialysis machines delivered steady stream and they learned that not all the blood was circulated (some pooled).
Not that I'm 100 percent sure about this. I like my ticker. I mean, with a non-pulse heart, if I were to pass out, they'd think I was dead.
What those who want activist courts fear is rule by the people.
Planaria have a unique system for excreting nitrogenous wastes. They have a secondary circulation system called a protonephridium, which consists of a connected system of "flame-bulbs." They essentially look like bulbs, with slits on the sides. At the top is a cap cell, which has cilia that descend into the hollow bulb. The cilia constantly spin, drawing water continuously, like a turbine, from the interstitial fluid through the slits. The reason they're called flame-bulbs is that the constant spinning of the cilia resembles a flame.
My pulse is my biggest hurdle when taking high-power rifle shots at long rages (>600 meters). Without a pulse I could hold steady on a much smaller target. If you've never shot a scoped rifle, your pulse makes the crosshairs bounce with each heartbeat. You can slow your heart-rate down and time the beats, but it would still be nice to be able to hold steady on a 1,000 meter target and not have any movement. If you get excited it all goes out the window - if your pulse quickens you might as well be riding on the back of a horse.
I imagine there are other tasks besides shooting that are impacted by pulse. I'm sure there are types of micro-surgery for example that could be negatively impacted by the surgeon's pulse.
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One of the factors that limits performance in athletic contests such as the recently completed Tour de France is cardiac output -- how much blood the rider's heart can pump. Fifty years from now will we have to have rules against riders with artificial hearts because they have an unfair advantage in cardiac capacity? Or will we borrow the kinds of regulations that the various auto racing organizations impose on engines? You can have an articial heart, but volume pumped must be constrained to be below X liters per minute, or the outlet into the aorta must be less than some number of square millimeters?
Actually, for most of evolutionary history, women had many fewer menstrual cycles than a "normal" woman these days. They were underfed, so had a later onset of menarche, and spent a much larger portion of their lives either knocked up or breast feeding, all of which means time not spent menstruating.
Bottom line is that the idea of "regular" menstrual cycles going on forever and ever from 13 to 50 is basically a modern made-up invention.
The wires running to the heart, called 'pacer leads', are not replaced, though, so it's just a simple matter of slicing open the skin and hooking up a new pacemaker to the lead. (Usually they have two leads, so they can pick which ever one seems better, and have a backup if one breaks.)
Now, what would be vaguely useful would be a way to recharge them from outside, by induction, or, hell, body motion. They can be programmed from the outside, but not charged, which I think is stupid.
Of course, pacemakers use a lot less power than artifical hearts. Pacemakers just give the heart a very tiny shock to get it to automatically work, because the heart's natural pacemaker has been screwed up somehow. A lot of times they only have to do it every few seconds or so. Artifical hearts have to move a hell of a lot of blood continually around the body, whereas you could probably operate a pacemaker from a watch battery for quite some time.
I have some old pacemakers laying around (They give you the old one when you get a new one. Weird, eh?) and I've been tempted to take then apart to see how much is the battery. I suspect 90% of them.
If corporations are people, aren't stockholders guilty of slavery?
Another problem that could occur... imagine if said transplantee were involved in an accident, and he got hurt, was unconscious. The first thing the rescuers would do would be to look for a pulse. On not finding one, would probably pronounce the victim dead at the scene and make no attempt to rescue him and get proper medical attention.
-- Soruk
(tongue-in-cheek) Actually, many of the myths about vampires come from an ancient civilization with advanced technology who achieved hugely increased life spans by use of cybernetics as well as organ and blood harvesting from less advanced humans. Because their hearts were mechanical, not organic, the only way to stop the heart from beating was to physically damage the heart itself. Even if you fatally wounded a vampire, its heart would not stop pumping. Hence the myth that the only way to kill a vampire is to steak it in the heart.
Mathematics is not a crime.
Ok, so you've got a magnetic impeller inside as well as coiled wire to drive the impeller. Then you've got a big ass electromagnet outside... maybe this isn't such a good idea after all.
I left the name off. I figured that some would know what I was talking about, most wouldn't care, and there's a few folks 'round here that might use it to wind up on the 11 o'clock news doing a "perp walk."
I've got a copy of at least one strip with 30 sec. of asystole in between SVT and NSR. Finding it would be the trick. The one I wish I'd have kept was from the guy in fine v-fib. Arrest witnessed by physician who didn't know CPR, down 5 minutes, when I called "clear" his eyes bugged out, he sat up and tried to strangle me. Scared the folks I was with, but I was more concerned with keeping my thumbs off the little red buttons. He screamed "NO!" in my face. After we pried him off me, we shocked him and got him back. Fellow actually woke up in the hospital...with no memory of why he'd yelled "NO!" I've always wondered....
I never had anyone respond that way to Adenocard.
Unsedated cardioversion is a completely different story.
"Sir, you're not going to like me after I do this."
"That's ok. I don't like you now."
This sig seemed like a good idea at the time....
Do you mean in the research labs or out in the public? But, not long, it's going there. Induction is too slow, RF is already there for some pacemakermanufacturers. A pacemaker collects a lot of data (Intracardiac electrograms) and higher datarates is needed to move that data to a computer where the physician can analyze it. So, prepare to ssh into your pacemaker.
it's called organ "donation" for a reason... it's also called an anatomical "gift." You're giving somebody else life, with something you no longer need; it's strictly voluntary...nobody's going to force you.
So You're going to die and bury that organ... yet you're going to try to scratch and scrabble for that last thin dime, even as you die? You refuse to take part in a process that benefits others, simply because you cannot benefit yourself? No streak of altruism? Not one iota of selflessness in you? You were given life... yet you insist on being paid for giving others life, via something you were just going to throw away to rot?
Hmmmm... I'm guessing I won't be seeing you volunteering down at the homeless shelter much... suit yourself.
Even if a man chops off your hand with a sword, you still have two nice, sharp bones to stick in his eyes.
This is an interesting idea which sounds plausible. It's well known that our circadian rhythm is driven by pulsatile activity of our pineal glands, as well as certain nuclei in the brain. And reproduction is impossible without pulsatile release of GnRH (gonadotropin releasing hormone) from the hypothalamus. In fact, menstrual cycles can be stopped by providing a continous level of GnRH, whereas a pulse of GnRH will restart them again. Where do these pulsatile mechanisms in the body derive their timing from? What if it's from the heart? After all, the heart is one of the earliest organs that start functioning in the embryoobstetricians generally use the lack of a heartbeat on ultrasound as a sign that a miscarriage has occurred. Who knows what pulsatile processes will be driven out of whack by eliminating cardiac pulsatility?
As an aside, there are an awful lot of posts here looking for problems and generally being pretty negative on the whole idea. It really says something depressing about the general tone of Slashdot at the moment. I wonder if it has occurred to any of those posters that the developers will have thought of these problems too, and either solved them or determined that they are not significant?