Advanced Technology

[DaleC]

Yes, this would fit within the small segment maximizing potential.
But I also see other complications. We would still be limited by the material requirements to maintain body temperature and re-oxygenation of the liquid medium and I think bailout strategies would be far more complex.

 

[EFX]

I think the two biggest hurdles to get over are what Akimbo mentioned in an earlier post: (1) Can we initially flood the lungs with liquid and maintain an adequate flow without collapsing the aveoli and, (2) can we dry out the lungs in time to allow gas breathing without drowning the diver. Everything else I view as solvable engineering problems (i.e., pumping, adding O2 and removing CO2, maintaining the liquid temperature, etc.).

I see TLV for exterme depths, certainly below 1000 ft or shallower depths for very long periods of time. OC scuba beyond 400 feet becomes a logistic nightmare with multiple stages and deco bottles. A rebreather helps with smaller tanks and a bailout bottle. For depths beyond 400 feet rebreathers are the way to go. Whether OC or CCR the deco obligation for very deep dives becomes overwhelming.

If your sinuses and ears can go on liquid then bailout is as simple as inflating your BCD to the max and rocketing to the surface. A pressure relief valve on the BCD will keep it full and prevent it from exploding. Going back to gas underwater can't be done so carrying bailout bottles of gas is needless.

One web site said that they have been successful treating neo-natal infants with PLV (partial liquid ventilation). Their alveoli probably arn't developed to the point where a liquid could collapse them but at some later time they have to dry out sufficiently to go 100% on gas.

If the two issues above present no problems for adults then it is my guess that somewhere there are divers already diving on TLV. They would be military doing highly covert dives and/or commercial divers doing long deep dives. Whatever the mission the present gain would need to outweigh the future possible cost.

 

[DaleC]

Yes, but then what. You've had a failure of your liquid system and rocketed 1000ft to the surface. Are you just bobbing around hoping the rescue team will find you, recover you, and connect you to a secondary liquid unit in time (assuming you always dive in fair sea states). Will I knock myself out hitting the hull or get cut up by the prop?

Also, is your stomach and gut filled with liquid and what about the gasses of digestion? The longer you're down, the more they build up, the more they expand no?

 

[EFX]

If you don't come up a line then an alerting device similar to the life line GPS can alert the crew and get you out of the water ASAP. They would invert you to drain the liquid while breathing on pure O2 gas. Ascending without a collision is probamatic but you can slow your ascent just before reaching the surface and check for obstacles. Gasses produced in the gut are not at the same density as the same quantity of compressed gas breathed at depth. Therefore, they do not expand during the ascent. There probably isn't enough gas produced to expand the volume beyond its already highly compressed volume. A flap is needed to cover the esophogus to prevent the liquid from being ingested.

 

[DaleC]

Are you sure...
I think you will find that the gut has pain receptors that are very sensitive to expansion and 1000' equals travel through approx. 30atm's. Are you sure one would not produce any flatulent gas or have to belch? How does that work (belching) breathing liquid media. How do you suppress that?

 

[EFX]

In a previous post I mentioned that in order to circulate the liquid through the lungs two tubes would need to be inserted into the trachea. The supply tube would be lower in the trachea than the return tube. Assuming the sinuses and ears are flooded the gas would be trapped. I guess you wouldn't be able to eat pepperoni pizza before the dive.

 

[victorzamora]

They would invert you to drain the liquid while breathing on pure O2 gas.

That sounds like a pleasant experience.....especially when one is already stressed out from the rest of the emergency.

 

[EFX]

You probably need to invert even after a non-eventful dive in order to clear the lungs as rapidly as possible. In an emergency the support team, after getting you on the boat, could also connect another liquid source into your hoses. After you're stabilized you can begin the process of removing the equipment. My guess is that going on liquid would be easier but not much fun either. You need to get two small tubes down your trachea. You may feel like you're suffocating in the interval during the initial flooding.

Another thing to ponder. If the breathing response is triggered by CO2 and CO2 is continuously swept away by the liquid will your lungs need to breath? That is, will they need to expand and contract? If not, you would feel fine but you're not breathing. That would be a very unsettling feeling.

---------- Post added September 23rd, 2014 at 05:08 PM ----------

The rapid ascent for liquid is what a CESA would be for scuba. Another option for "bailout" is to provide the dive team with a spare system they can take down with them. If there's trouble, the tubes from the spare system could be hooked to the failed system's tubes to support the diver on the way to the surface in a controlled moderately fast ascent.

Here's questions for mechanical or system engineers:
Given the flow rate of 15 L/min (7 L/min for a resting diver) for a 200 lb diver what size motor and battery would you need? These would be carried on the back in a unit similar to a CCR. Are the sizes and weight reasonable for divers? What is the minimum diameter of the tubes needed to support this flow? If the tubes are bundled together by a thin skin will they fit down the trachea? Assume perflourocarbon which has twice the density of water. How many ampere-hours are needed and how long will the battery last? If the pump fails can mechanical levers actuated by the diver provide enough flow (assume 7 L/min flow rate)?

Here's questions for process or chemical engineers:
What technology could be used to oxygenate and remove CO2 in perflourocarbon? Can the transfers be made at the flow rate above or do we need a resovouir? Also, we need an inert gas for mask clearing and BCD filling but can we use a liquid or semi-solid source for oxygen? Would this be more compact than taking a gas cylinder? Is this even feasible? Stretching the limits of technology can we draw O2 from the water and transfer enough of it to the breathing liquid medium at the required flow rate? If the flow rate can't be met what percentage of teh total O2 needs can be met and is it feasible?

Here's questions for medical field people:
If a liquid could remove CO2 from the lungs would the lungs still breath (i.e. expand and contract)? How delicate are the aveoli? Drowning victims seem to recover fully without large scale damage to their aveoli. Can the aveoli withstand pressure from a liquid at twice the density and for dive times lasting far longer than a drowning assault? Assuming the lungs are completely flooded with liquid can they sustain the weight in and out of the water? The density of perflourocarbon would be 124 lbs/ft3. Multiply this by the minimum lung volume to get the weight.

 

[DaleC]

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.

Wet drowning victims (those whose lungs fill with water) often succumb to secondary drowning, aspiration pneumonia, as the result of irritation of the lung tissue. The same would probably occur with liquid media and is probably the cause of deaths post experiment considering the irritation involved in liquid tidal flow.

The machine used for taking O2 out of water is called a mechanical gill.

All your questions re gas transfer will ultimately show that liquid media seems too complex for human use and would probably be bypassed by heart/lung machine technology to perform extra corporeal perfusion, thus bypassing the lungs altogether. This basically is a blood scrubber, in the same way rebreathers use air scrubbers. The technology exists and is already routine for surgery.

Mount one on your back, plug yourself in using large bore catheters, and forget about breathing altogether. You could do it today if you wanted to. All you need is a doctor, a machine, and a bathtub.

 

[EFX]

The addition of CO2 to the liquid would make it lighter and thus would aid in convection to get the liquid moving out of the lungs. It would be replaced by oxygenated liquid. This might create small loops in localized areas to support the needed O2/CO2 gas exchange.

Blood scrubbers are intriguing but how do you control the bleeding on and off the machine? Another problem is how do you keep the loop clean? A patient lying on a sterile surgical table in a clean room is quite different from a portable unit going down to Davy Jones's locker, that needs periodic cleaning by the user. How do you prevent contamination of the blood? Even if you don't need the liquid for breathing you still need to fill the lungs with a liquid to offset the ambient pressure. Gasses won't work because of the same limitations that have plagued us from day 1.