Advanced Technology

[DaleC]

As to managing ECP: how they routinely do it in an OR could more easily be replicated in an aquatic setting than trying to perfuse the lungs with liquid, which no one currently does anywhere. The first only requires site specific tweaking while the second attempts to overcome evolutionary changes that separate us from fish (gills vs lungs).

Why do you need to fill the lungs with liquid? What specific problems are you trying to overcome. Freedivers now descend on a single breathhold to 700' Herbert Nitsch - Wikipedia, the free encyclopedia
If that freediver's blood could be scrubbed and replenished by a backpack machine it is theoretically possible he could prolong his dive to the point that other factors limit it (fatigue/cold). The liquid media is really a transition technology that contains more problems than solutions. Once you can scrub the blood effectively the whole idea of using the lungs becomes mute. You could locally anesthetize them and be safer than attempting to fill them with liquid. Once you surface you counteract the anesthesia, begin breathing and go off the mechanical loop.

 

[EFX]

The problems I'm trying to overcome using gasses are the same problems we face now on scuba. You might be assuming that free divers don't ongass N2 but they do. The reason they don't suffer from any of those problems is that they don't stay long enough at depth and the N2 supply is fixed at the surface. I went through the physics and did some calculations using dive tables on another thread but I'll summerize here. A free diver going to any depth is subject to pressure forces exerted by the water. For the free diver the lungs are a flexible closed container where the pressure in the lungs equalizes with the ambient pressure as the lung volume is decreasing. The partial pressures (pp) of the individual gasses that make up air are also increasing. At 700 feet, if we ignore the ongassing on descent, the pressure drop between the lungs and the tissues for the N2 will be approximatly 22 x 0.79 - 0.79 or 17.4 atm. Because the supply of N2 is limited (we're on breath hold) the amount of N2 that actually get absorbed is limited. The problem for our deep diver who is staying longer at depth is that sufficient N2 may be absorbed which may require deco. The amount of ongassing stops when the ppN2 reaches half of the starting pressure drop.

Nitrogen narcosis may also be a factor with increased N2 in the tissues. Another problem is the risk of collapsing a lung because there isn't sufficient air in the lungs to balance the increasing ambient pressure as the diver goes deeper. Also keep in mind that as N2 diffuses out of the lungs the lung volume is going down. This will limit the maximum depth. If you reinflate the lungs to maintain a safe volume ongassing will start again and stop at half of the new starting pressure drop. This increases the N2 loading in the tissues.

Anestesia may not be safer as some of that chemical may get transferred to the blood stream and we don't know if the anestestic effect gets amplified with increased pressure. You still have the problem with piercing not one but two major veins or arteries and the subsequent problems with bleeding. If you're making repeated dives over a long period you will have repeated piercing. A semi-permenant catheter also presents long term problems not to mention blood contamination. I don't work in the health care industry but I think hospital staff take great pains to keep everything clean and people still get infected. Imagine a diver prepping for a dive on a boat that's loaded with contaminants floor to ceiling, bow to stern. I don't see how this is simpler or managable for the diver at the surface let alone at 2000 feet. No thanks. I'll stick with TLV.

Make your dive on ECP. I'll come and visit you in the hospital as they're treating you for sepsis.

---------- Post added September 24th, 2014 at 10:06 AM ----------

Gas exchange (O2/CO2) occurs at the capillary membrane of the aveoli, the terminus point of a decreasing diameter branching system; it's not a loop. Breathing in and out exchanges all volume in the lungs, with each breath, (in layman terms as there is some residual volume that does not exchange). Imagine trying to create this same exchange with fluid, in tissues as delicate to over-expansion as the lung. How else could you do it without compression and expansion of the lung.

I'd like to return to this topic. You bring up a great point. I was thinking too much about the TLV machine and not enough about the human machine. I was assuming the liquid would circulate around the lungs to sufficiently remove CO2. The vast surface area along with the branching lung system probably makes this impossible by mechanical means alone. If this is the case and it most certainly is, there is a built-in feedback mechanism that aids liquid circulation -- the lungs will start to breath! As the CO2 builds up because of poor circulation the lungs will begin to breath aiding the pumping action of the liquid ventilator. What is now required is check valves in the tubes. One in the supply and one in the return to maintain unidirectional flow.

The higher viscous fluid will slow down the breathing rate due to the flow constraints of the mechanical system. Will this be a problem? I don't know. The slow rate limits the O2/CO2 transfer compared to gas but here again TLV helps us. Perfluorocarbon can absorb O2 more than 3x that of blood and 12x greater for CO2. This means less breathing cycles are needed. See Liquid Ventilation for more information. Also, see Liquid breathing - Wikipedia, the free encyclopedia.

 

[DaleC]

I do work in health care and that's why I am trying to base my ideas in what I know is feasible.
Kidney disease survive repeated blood scrubbing (hemodialysis) 2-3 times a week. I witnessed my father do it for a year in an outpatient mall clinic. Not that difficult. The semi permanent catheter thing is called a stent - current technology. No one bleeds out and infection control would certainly be less than filling and draining the lungs with fluid in the field.

As far as infection goes. Something you may not know is that the lungs can fill with fluid in a bad way (pneumonia) even if sterile procedures are maintained. Primarily due to irritation or an over stimulated immune response. The airways have certain evolutionary strategies to keep foreign substances out (hairs in nose, gag/cough reflex, epiglottis) (because the consequences are dramatic) which you will bypass by filling the lungs with your fluid, a very invasive act. If you could dry out the lungs, as you suggest, why don't they do that now to save the lives of the millions who die from pneumonia? It's not that easy.

Anesthesia is a known science. Again, when looking in comparison at what you are proposing, not that difficult. It's all current technology that just needs to be adapted to a non traditional use.
Off the net from a pre op info site:

"You'll be given medicine to stop your heartbeat once you're connected to the heart-lung bypass machine. A tube will be placed in your heart to drain blood to the machine.
The machine will remove carbon dioxide (a waste product) from your blood, add oxygen to your blood, and then pump the blood back into your body. Your surgeon will insert tubes into your chest to drain fluid...Once your heart has started beating again, your surgeon will remove the tubes and stop the heart-lung bypass machine. You'll be given medicine to allow your blood to clot again."

 

[EFX]

I do work in health care and that's why I am trying to base my ideas in what I know is feasible. Kidney disease survive repeated blood scrubbing (hemodialysis) 2-3 times a week. I witnessed my father do it for a year in an outpatient mall clinic. Not that difficult. The semi permanent catheter thing is called a stent - current technology. No one bleeds out and infection control would certainly be less than filling and draining the lungs with fluid in the field.

OK. If ECP is that easy why hasn't it been adopted by divers?

If you could dry out the lungs, as you suggest, why don't they do that now to save the lives of the millions who die from pneumonia?

They don't do it now because the fluid is water which acts as a barrier to O2/CO2 transfer. PFC does not have this characteristic. I'm advocating a gravity drain of the PFC by inversion. I assume this would leave a thin film of PFC in the lungs. I don't know how quickly the remaining PFC can transfer O2/CO2 from the gas but it has to be much higher than water.

Anesthesia is a known science.

Why is anesthesia necessary?

I do have a solution for the lung pressure problem that I think can be solved with ECP. Let's fill the lungs with gas and use the scrubber to remove N2. That takes care of deco and N2 narcosis. The gas could also be used for bailout. However, we're stuck with equalization and fast ascents cannot be done. We're also back to gas management issues -- keeping ppO2 under a max value. This can be handled by CCR technology.

And.....I thought of something else our ECP machine can do. For really long dives we can inject nutrients and water into the blood to keep us nourished. For older guys, and for a modest increase in cost, we can have it inject Viagra. Then we'll be ready to go after the dive. Hey, I'm beginning to like this option.

 

[DaleC]

Why external perfusion is not adopted for diving is the same reason liquid media is not.. the returns are not worth the risk/investment. The activities that would require such technology are miniscule and can be served by current practices (sat diving/exosuits/minisubs/ROVs) with relatively little risk to human health. Common sense dictates we do as much as we can with current means before moving on to the next level. I believe there is simply nothing currently worth doing underwater that warrants the amount of research and risk to health that either strategy would require.

As to anesthesia.
Sometimes we think humans breath liquid in the womb and can return to that state but this is not true. What happens there is very much like my external perfusion model (so there is precedent for its viability at least). The heart beats to circulate blood which is scrubbed externally at the placental membrane via the umbilical cord. What also happens is the lungs do not breath. This only occurs after birth when the baby is disconnected from the blood scrubber and switches to lung scrubbing. To make the ECP model work the one thing you need to do is stop the lungs from breathing, which is an autonomic response. We can't control it voluntarily. Thus local anesthetic or, allowing the lungs to do what they want by breathing an inert gas. I honestly don't know how lungs would behave if the bodies gas exchanges were met by blood scrubbing.

 

[EFX]

Why external perfusion is not adopted for diving is the same reason liquid media is not.. the returns are not worth the risk/investment. The activities that would require such technology are miniscule and can be served by current practices (sat diving/exosuits/minisubs/ROVs) with relatively little risk to human health. Common sense dictates we do as much as we can with current means before moving on to the next level. I believe there is simply nothing currently worth doing underwater that warrants the amount of research and risk to health that either strategy would require.

I think you have this backwards. The activities using todays technologies are miniscule because they limit what we want and can do. The equipment and support needed are expensive and complicated compared to a diver with his own gear and perhaps a couple of surface support people. Think of a scientist going down to research the envirnment at 1500 feet. Think of everything a scuba diver can do in shallow water vs. any of the technologies you list above. The problem isn't that we can already do what we want so why take the risk but that the risk/benefit ratio is too high.

 

[descent]

The idea is so romantic. I would love to see a real one. But ...

Replacing Mother Nature's gas ventilation circuit with an extracorporeal apheretic circuit for use at depth would be a large engineering challenge.

Like, "new airliner family" large.

The machine would need to scrub CO2 efficiently using the smallest possible volume of blood, while precisely regulating serum volume, temperature, PH, isotonicity and pp02. Externally. Using a waterproof, portable power supply. In salt water. In conditions arguably more hostile than vacuum.

After the system is designed to support sedentary metabolism with NASA-level reliability, we have to redesign it to support several orders of magnitude increase in throughput for stress- and exercise-related emergencies.

While keeping the NASA-level reliability, of course.

Even the mechanical connections are still largely in the science fiction category.

The shunt anticoagulation technology must walk a narrow path. It must not promote thrombosis OR hemophilia. It should have safe behavior over a wide range of temperatures. That behavior should degrade in a friendly, linear way. This problem is not "solved" to the point where we can sell people with renal disease an apheresis rig and send them home with an instruction manual and some bags of saline. Just plugging the machine into a human circulatory system requires a degree AND and license.

Symptoms of hypocalcemia and other citrate-induced metabolic abnormalities affect neuromuscular and cardiac function and range in severity from mild dysesthesias (most common) to tetany, seizures and cardiac arrhythmias.

... from the paper "Anticoagulation Techniques in Apheresis: From Heparin to Citrate and Beyond (Apr 24, 2012)".

Producing a small, portable, highly-reliable machine of this complexity would require careful field testing and due diligence. It seems likely that this testing (and sales of initial versions of the unit) would kill a non-trivial percentage of early users.

Even the power supply would have to be astonishingly robust.

In a deep research / exploration scenario using medically-hybridized humans, would you be able to depend on a Tesla-style computer-controlled tray of Li-Ion cells? Are you willing to accept the occasional diver death because bugs in the battery tray environmental code sometimes cause runaway overheating? We can stop those with analog circuit breakers. Would you want to be troubleshooting a power outage and flipping circuit breakers with fifteen hundred feet of sea water between you and a safe breath of air?

How could you design a tool like this in good conscience while specifying a power supply less reliable than a plutonium RTG?

 

[Akimbo]

I think you have this backwards. The activities using todays technologies are miniscule because they limit what we want and can do…

I agree with descent… romantic. The activities with today’s human-intervention technologies are operationally expensive, thus limited in use. ROVs (Remote Operated Vehicle) have made manned submersibles virtual dinosaurs. They can operate much longer without downtime, can use smaller/less expensive vessels, and the greatest danger to human life is boring the operator to death.

Saturation divers still find some work on man-made devices, for now. This is primarily because of yet to be reproduced capabilities of the human hand. Force-feedback manipulators are pretty good, but that represents a small portion of the sense of feel.

… Think of a scientist going down to research the envirnment at 1500 feet. Think of everything a scuba diver can do in shallow water vs. any of the technologies you list above. The problem isn't that we can already do what we want so why take the risk but that the risk/benefit ratio is too high.

The reality is there is very little if anything that a scientist needs to accomplish in deep water that can’t be done with a ROV — and in some cases better. After you get below the 300-600' light penetration range the density of life becomes a tiny fraction of what recreational divers experience. That density drops again below the 1000-2000' range where shallower life can transit. With lower density comes far greater distances that need to be covered… becoming the realm ROVs and AUV (Autonomous Underwater Vehicles).

Technologies that enhance ROVs and AUVs are progressing at a very rapid rate so the likelihood that underwater liquid breathing will ever be developed is looking lower. This dismal outlook likely applies to manned space missions and fighter pilots.

There is no recreation market for diving below the light penetration range. The ocean at that depth is a featureless gray mud bottom occasionally interrupted by a few rocks, which is the main reason I lost interest in the manned submersible and ROV business in the 1970s. It is sad then the most interesting feature found in days of surveying is a discarded Pepsi can.

 

[EFX]

While keeping the NASA-level reliability, of course.

You don't need NASA-level reliability, that is, triple redundancy if that's truly what you have in mind. Simple redundancy is all you need and I've already explained this for TLV and ECP with gas bailout. Today, deep divers on CCR have one redundant system if their CCR completely fails, and that's an OC bottle which is enough gas to get them to the surface.

The reason NASA requires triple redundancy for space missions is that there is no escape from space (or from any extraterrestial body) to the earth and no one else to help you. If your primary fails early and you go on backup you may not be able to get back in time before your backup fails, hence the need for a backup to the backup. In the deep ocean on either "romantic" system you can always get to the surface on your backup where there is both support and air (or another liquid system) to breath.

Even the power supply would have to be astonishingly robust.

In a deep research / exploration scenario using medically-hybridized humans, would you be able to depend on a Tesla-style computer-controlled tray of Li-Ion cells? Are you willing to accept the occasional diver death because bugs in the battery tray environmental code sometimes cause runaway overheating? We can stop those with analog circuit breakers. Would you want to be troubleshooting a power outage and flipping circuit breakers with fifteen hundred feet of sea water between you and a safe breath of air?

If you posted complete gibberish in swahili I probably would have understood it better than what you posted above. The only thing I can extarct from what you posted is that you appear to be familiar with systems that interface to multiple power systems (mains and UPS alternator/battery). If ECP can ever be realized despite the formidable obstacles you present, then there will have to be some simplifications without sacrificing robustness.

 

[DaleC]

As Akimbo says, aside from working divers, there's just not that much for a free diving human to do down there. Probably the biggest activity would be sampling which an ROV can do quite well.

There is also a psychological element to what you are suggesting that can't be over looked. From my experience solo diving I think the separation from human support or positional referencing that a lone naked diver would experience at extended depth/darkness would be too intense for all but a few. It would be like sending a man into orbit without a shuttle or space station. The sense of scale and lack of spacial reference points would be immense. But unlike space, the diver would not see any features up, down or around them. I suspect it would be similar to the experience of sensory deprivation.