Slashdot Mirror
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?"
How would your life be different without a pulse?
I would have had much more in common with my ex-wife.
Trolling is a art,
FTA: "The pump also has a curious side effect: people implanted with the device have no pulse."
/dies
They had better put an obvious port on it so paramedics know it's there before sending voltage through.
I can see the first really drunk guy with one of these taking a nap on the beach:
"ZZzzzzzzZZZZzzzzzZZ"
"Sir!"
"Oh my GOD! He's Dead, Jim!!!"
"He's got no pulse! Call an ambulance!"
(ambulance arrives, 10min later)
"This man has no pulse! I've been giving him CPR since I called you guys and I can't get a signal!"
"CLEAR!!!!!!!!!!!" "ZZZZAPP!!!!"
The dangers of knowledge trigger emotional distress in human beings.
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.
http://alternatives.rzero.com/
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.
I wonder how many goth vampire wannabes will elect to have these implanted, just to improve their authenticity?
I guess they'll just put a timing light on my, er, finger, and check my RPM.
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.
- First they ignore you, then they laugh at you, then ???, then profit.
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...
90% of the wealth is in 2% of the pockets. Bummer to be in the majority.
"Must have a pulse" is no longer a requirement. :-)
dinner: it's what's for beer
Well, that and the guy you just checked screaming "OW! You just pinched me fucking ear!" will probably help as well.
Perhaps I should have clarified some of this for the non-biologists here. Baroreceptors are receptors found in the aortic arch and internal carotid arteries that are sensitive not only to overall pressure in the cardiovascular system, but also to rates of pressure changes which are critically important in cases where you suddenly undergo rapid loss of blood pressure. (like when you are bleeding......alot). In cases like these, your body starts a series of physiologic changes to keep you alive and interfering with those sorts of things were what I was referring to.
These issues may also be important for maintaining cardiovascular fitness as well as recovering from myocardial infarcts, and because the alternating pulse pressure is eliminated in turbine models, I would worry about possible losses of negative feedback which might result in runaway blood pressure which could lead to hemorrhagic strokes, kidney damage and other such unpleasantries.
Oh, and since the Slashdot crowd appears to be preoccupied with sex, there is some evidence that penile erections are dependant upon alternating pressures to, ahem.....get the job done.
Visit Jonesblog and say hello.
The again, not having a working heart at all would probably undermine those mechanisms as well...
Only arteries have a pulse. The blood flow is as follows: heart -> arteries -> capillaries -> veins -> heart. By the time the blood gets thru the capillaries to the veins the blood pressure is vastly reduced and the pulsatile flow generated by the heart is not felt in the veins. Hence veins do not have a pulse. The valves in the veins have nothing to do with the pulsatile flow of the heart and hence a constant flow heart will not affect the functioning of the veins in any way. Venous problems like varicose veins, cirrose like vena portalis deformities are not related to how the heart pumps.
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.
You don't have to spell it out, we're all familiar with that acronym.
^^vv<><>BA
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.
> (IMAD) I am a doctor.
;-)
Good thing your patients' lives don't depend on your ability to create acronyms.
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.
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...
I'll bite: I'm not golfing because I don't have the patience. IAAS (I am a Surgeon) and it would not be that difficult to measure a continuous flow generated pressure instead of a pulsed pressure. Plus you wouldn't have to teach us about turbines and such. For example, currently a patient in the ICU may have their blood pressure measured with an indwelling arterial line rather than a transduced cuff. We follow Mean Arterial Pressure (MAP) in this setting. Here's a quick definition: http://www.globalrph.com/map.htm (It was easier to google than find a textbook but this is short and sweet)- "Equation: MAP = [(2 x diastolic)+systolic] / 3 Diastole counts twice as much as systole because 2/3 of the cardiac cycle is spent in diastole. An MAP of about 60 is necessary to perfuse coronary arteries, brain, kidneys. Usual range: 70-110." We could still measure the equivalent of a MAP with a continuous pump. Some of the bioengineers who commented above probably know better, but whatever the range of pressure in the system from continuous pumping (whether it's always the same or if there's a smaller variation than the normal systolic/diastolic) it could still be accounted for and easily monitored and used to guide therapy. Probably the bigger problems are those already mentioned: baroreceptors that will now be in a new range, changes in coagulation, and destruction of blood borne cellular elements.