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Distributed Circulatory Assists

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The human heart can pump the body's entire volume of blood every single minute - and not just in a straight line, but through a maze of twisty passages, all different.

Most cardiac assist and heart replacement devices try to fit inside the chest, and there's not a lot of room in there. So I propose a group of stent-like devices placed at strategic points inside various larger arteries (e.g., ascending & descending aorta, the carotids, others) where each would take up less space than a complete heart replacement - but each would only have to move a smaller volume of blood than the heart handles by itself. As blood is salty enough to conduct electricity, the stents could be tiny magnetohydrodynamic accelerators; non-mechanical pumps to avoid damaging any blood cells.

Haven't quite worked out a power supply though (nuclear battery?); what field strength would be required; or if having one or more such devices in the body would cause any problems more serious than getting through airport security.

kdf, Oct 30 2020

MHD https://en.wikipedi...gnetohydrodynamics.
[kdf, Oct 30 2020]

Ventricle assist devices https://en.wikipedi...ular_assist_device/
Many are continuous flow, pulse-less [kdf, Nov 01 2020]

Possible side effect of magnetic fields on blood https://physicsworl...ce-blood-viscosity/
Favorable - reduced viscosity? No need for anti-coagulants. [kdf, Nov 02 2020]

MHD pump applications https://www.science...i/S1110016816300126
[kdf, Nov 02 2020]

Wikipedia article mentioning induction devices https://en.wikipedi...amic_drive#Typology
Might sole electrolysis problem [scad mientist, Nov 03 2020]

Shape memory alloy - cardiac assist https://www.ncbi.nl...rticles/PMC6394801/
Technical Feasibility and Design of a Shape Memory Alloy Support Device to Increase Ejection Fraction in Patients with Heart Failure [kdf, Nov 03 2020]

Shapeflow Shapeflow
The game emulating human survival. [Inyuki, Nov 04 2020]

Procyrion’s intra-aortic pump https://www.medgadg...y-support-pump.html
[kdf, Nov 04 2020]

Wireless heart pump https://www.medgadg...-contact-blood.html
Wraps around the outside of the aorta [kdf, Nov 04 2020]

[link]






       This could be used in conjunction with a g-suit to enhance the performance of combat pilots. [+]
8th of 7, Oct 30 2020
  

       //magnetohydrodynamic accelerators//   

       How do those work?
pertinax, Oct 30 2020
  

       "could be used in conjunction with a g-suit to enhance the performance of combat pilots"
-8th of 7, Oct 30 2020
  

       [previous rambling about veins removed]
[replacement text: You're right. I was only thinking of arterial stents originally. But venous stents would be possible also. Good one!]
  

       Side note - I specifically thought of the Borg when I was cooking this one up. Is there any place in ST canon where Borg technology has been used for human medical treatments?
kdf, Oct 30 2020
  

       Pertinax - "A magnetohydrodynamic drive or MHD accelerator is a method for propelling vehicles using only electric and magnetic fields with no moving parts, accelerating an electrically conductive propellant (liquid or gas) with magnetohydrodynamics." Source: Wikipedia (linked)
kdf, Oct 30 2020
  

       // Borg technology has been used for human medical treatments? //   

       Yes, of course, in the Voyager episode ... wait, you mean you don't KNOW ?   

       What sort of a Trekkie are you ?
8th of 7, Oct 30 2020
  

       Not any sort of Trekkie. I have a broad base of knowledge but not very deep in some areas. As with all other things, I consult experts when necessary. Please, expound on the theme of applied Borg technology (short of assimilation) in human medical practice.
kdf, Oct 30 2020
  

       Given that the total length of an adult's blood vessels is better than 60,000 miles (over twice around the earth) some assists here and there make sense.   

       Additionally for every pound of fat another mile of vessels are required, an additional strain on the heart.
whatrock, Oct 30 2020
  

       "for every pound of fat another mile of vessels are required"
-whatrock, Oct 30 2020
  

       An interesting detail but one I would question. Do the blood vessels get discarded or put in storage if I lose weight, or do they just shorten if the distance between various body parts shrinks? And what about going the other way, bulking up by adding muscle mass? Does muscle growth require new mileage of blood vessels, or stretching existing ones?
kdf, Oct 30 2020
  

       Angiogenesis, the second book in the bible.
whatrock, Oct 30 2020
  

       //a dark maze of twisty passages, all different.// - nice 1970’s text adventure computer game reference there
hippo, Oct 30 2020
  

       There is a relationship affecting the heart stroke and power with the factors of capacity and stretch of the volume coming out in the maze. Playing about with a few extra tiny asynchronous pulses will take some work to get the supplementary pumps timed just right.   

       Because of complexity, I wouldn't put it past the body to have heart cells that alter slightly depending on the biochemistry of the pulse volume. I wouldn't want to see biochemical signals negated or changed by mechanical wave fronts.
wjt, Nov 01 2020
  

       “asynchronous pulses”
-wjt, Nov 1 2020
  

       No. These would offer a continuous flow, rate changing constantly based on the body’s needs. No “pulse” at all. This is already the case with some existing ventricle assist devices (link).
kdf, Nov 01 2020
  

       //blood... magnetohydrodynamic accelerators...//
That's quite brilliant. Have there been any (real-world) experiments with this? Blood, being somewhat more complicated than just salt water, might not like being subjected to strong e-m fields...
neutrinos_shadow, Nov 01 2020
  

       “strong e-m fields”
  

       Yep, needs more research. But likely no worse than mechanical devices in use now. Do the fields used in MRI - whole body exposure - mangle blood cells or affect circulation?
kdf, Nov 01 2020
  

       No, and they're several Tesla ... many orders of magnitude stronger than anything encountered by humans in a natural environment.
8th of 7, Nov 02 2020
  

       Oh well... here’s a showstopper for using MHD to move blood: Electrolysis. From link reviewing MHD pump applications ...   

       “Conducting fluid in the micro-channel of MHD micropump was studied by Jang and Lee. The micropump is driven by Lorentz force in the direction perpendicular to both magnetic and electric fields. The performance of the micropump is obtained by measuring the pressure head difference and flow rate as the applied voltage changes from 10 to 60 VDC at 0.19 and 0.44 T (T). The pressure head difference is 18 mm at 38 mA and the flow rate is 63 μl/min at 1.8 mA, while the inside diameter of inlet/outlet tube is 2 mm and the magnetic flux density is 0.44 T. It was noted that bubble generation by the electrolysis of the conducting liquid can be observed.“   

       ... back to turbines, I guess...
kdf, Nov 02 2020
  

       The Wikipedia article mentions induction devices that may solve the electrolysis problem: "Induction devices when alternating currents are induced by a rapidly varying magnetic field, as eddy currents. No electrodes are required in this case. As induction MHD accelerators are electrodeless, they do not exhibit the common issues related to conduction systems (especially Joule heating, bubbles and redox from electrolysis) but need much more intense peak magnetic fields to operate. Since one of the biggest issues with such thrusters is the limited energy available on- board, induction MHD drives have not been developed out of the laboratory."   

       One might expect the power requirements to be a problem, but you mentioned nuclear battery, so we should be good, right :)   

       Also, without really researching this, I'm imagining that this type of device can clamp on around the outside of the blood vessel so there might be less risk during installation.
scad mientist, Nov 03 2020
  

       The problem with clamping to the outside of the blood vessel is that installation requires more surgery from the outside. Stents are installed via catheter, much less invasive or damaging to surrounding tissue   

       This idea is even less than half baked so I’m open to suggestions for changes, but the idea of stent- like devices was really the root of it. Turbines instead of MHD, sure; alternatives to nuclear power, I’m all ears. But you shouldn’t have to cut the patient open in multiple places.
kdf, Nov 03 2020
  

       // Turbines //   

       Nononono, very bad. We see dead people. Dialysis and heart-lung machines invariably use peristaltic pumps - putting blood through any sort of a turbine will severely limit your life expectancy.
8th of 7, Nov 03 2020
  

       Turbines aren’t my first choice either, but they’re pretty common in existing pulseless VADs. I still prefer MHD though, as I think it could produce laminar flow, and be less damaging to blood cells. But if you insist on a pulse... How about a coil or mesh tube of shape alloy? Give it a charge at one end, and a wave-like ripple/contraction proceeds along its length before relaxing back into its original profile? Can it be made small enough to fit inside the aortas and carotids? And biocompatible so the patient isn’t on anticoagulants and immunosuppressants? And a useful service life of 10-20 years?   

       I’ll need your design spec before the 17th, so I can discuss with my cardiologist.
kdf, Nov 03 2020
  

       See, there really are no "new" ideas. *AFTER* I made the remark about shape memory alloys, I found (link) something pretty close to what I was thinking of - but wrapping the entire heart instead of inserting something in blood vessels. I wonder if I read that paper or a citation to it somewhere before and just didn't recall it properly.
kdf, Nov 03 2020
  

       What about a piezo-plastic tube working as a peristaltic pump? Could be inside or outside the blood vessel (inside = easier, outside = cleaner/safer for the blood).
I don't know how flexible piezo-plastics are, but I figure if it's small enough, it doesn't matter. And if it's just a single material doing the work, it can be scaled down pretty small (à la integrated circuits).
neutrinos_shadow, Nov 03 2020
  

       “induction devices”
-scad_mientist, Nov 03, 2020
  

       ... require alternating current and and much more intense peak magnetic fields to operate.
kdf, Nov 04 2020
  

       Is your idea inspired by the game of [Shapeflow]? (link) :) What you speak of, seem to be a result of thinking how to win that game. Good thinking [+]. Imaginably, those little assists around the body could do even more -- they could: absorb stuff and dissolve stuff, warm, cool, and do other things to ensure uninterrupted flows.
Inyuki, Nov 04 2020
  

       Inyuki - No, I’ve never heard of Shapeflow. This HB post came from a long riff about how far medical technology might go ... from repairing/replacing a heart valve, to more involved repairs, to making the heart itself redundant.
kdf, Nov 04 2020
  

       //Dialysis and heart-lung machines invariably use peristaltic pumps - putting blood through any sort of a turbine will severely limit your life expectancy.//   

       That's possible, but it's also feasible to design around that. The reason for using peristaltic pumps is much more to do with the fact that the blood remains entirely within a continuous stretch of disposable tubing the entire time. Sterilizing moving parts like impellers would be a nightmare. Out of interest, is the heart a peristaltic pump or a diaphragm? I'd go with it being a hybrid.   

       I have some Doppler recordings of blood flow with a marker of muscle contraction. To me it's obvious the heart muscle isn't doing anything for the last ~10% of each beat and the last part is sucked out of the ventricle through inertia/water hammer. I'd publish it if I had time/it benefited me in any way/I had any credibility in the field/publishing didn't cost a fortune.
bs0u0155, Nov 04 2020
  

       Maybe I'm going the wrong way with this. Veins have one way valves and any muscle action squeezes blood back towards the heart. Let's just* modify some of our larger arteries to do the same for outbound flow.   

       * By way of gene splicing** - or microsurgery - or hand waving magic.   

       ** Genes from an earthworm and our aorta can be powered like theirs.
kdf, Nov 04 2020
  

       THERE ARE NO NEW IDEAS.   

       Link - Pumps Inside Arteries Help Cardiac Patients" - from 2014. And once I found that, I found links for other related ideas we tossed about here.   

       DON'T YOU IT WHEN THAT HAPPENS?
kdf, Nov 04 2020
  
      
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