h a l f b a k e r y
What's a nice idea like yours doing in a place like this?
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Take the basic concept of a heart-lung machine, and adapt it for use underwater. Having a pair of catheters in your arteries probably isn't the most pleasant way to dive, but it has numerous advantages.
It completely eliminates problems caused by pressure. The lung machine can be enclosed in a strong
case, allowing the gas exposed to the air exchanger to remain at atmospheric pressure.
Without the need for high pressures, there is no set limit on how deep you can go. No need to worry about rise or dive speed either. No bends, no narcosis. Lower pressure also means less oxygen is wasted compared to breathing compressed air.
Since the machine constantly oxygenates your hemoglobin bypassing the lungs, you don't even need to breathe. Your mask will never fog up.
Free divers and the bends
The last answer on this link makes it look like your lungs aren't strong enough to expand beyond certain water depths. (I wanted to know the answer to the linked question anyway, but I never remembered to look it up until now) [Zimmy, Oct 10 2006]
Apparently the biggest obstacle is removing the CO2. if you're scrubbing the diver's blood, that problem goes away. Though there's still an issue with lung damage that we might want to fix before applying this to people. [DrCurry, Oct 11 2006]
||It's not the pressure in the lungs, it's the pressure in the bloodstream. having an external lung/oxygenating device won't affect blood chemistry. If, say, you were enclosing the whole diver in some unfeasibly strong suit, whereby normal pressures could be maintained inside, well then, no bends. otherwise, if any part of the diver is exposed to the oceanic pressures, then his/her bloodstream will be at that pressure. and will be subject to very high solubility for gasses such as nitrogen.
||good lateral thinking, but I really don't see how your idea solves the problem.
||[edit. About face. I'm not convinced that
Aq_Bi understands all the concepts
involved here, but the idea is more
workable than I originally thought.]
||It wouldn't prevent narcosis, either.
||You try hooking yourself up to a machine and trying not to breathe. You can't. Breathing is a natural reflex. You would end up filling your lungs with water, panicing and potentially damaging your lungs for ever.
||Reading up on how whales can survive their dives to great depths, I think that provided Aq_Bi replaces the air in the diver's lungs (to prevent them collapsing) and in the oxygen extractor with that liquid that you can breathe, this should work fine, with no decompression effects. Overcoming the breathing and choking reflexes may be problematical, though.
||Either way, I think this deserves a croissant.
||(If there's no nitrogen or other gas around to dissolve in the blood, you won't get the bends when it decompresses.)
||//It's not the pressure in the lungs, it's the pressure in the bloodstream.//
||This can't be true, else the liquid breathing system would suffer the same problems as gas. Liquids are incompressible. If the blood pressure changed to match the depth pressure, it would kill you very fast.
||As a separate idea, this could be modified into an artificial gill. With high enough surface area, extraction of oxygen from water is quite feasible. The biggest problem to overcome is hypothermia in anything but water at body temperature.
||OK... I've thought about it and I'm
reversing my opinion. With that, comes
price. I'm going to point out what I
||"Liquids are incompressible. If the blood
pressure changed to match the depth
pressure, it would kill you very
Not true. Liquids are (pretty much)
incompressible. That doesn't mean that
they don't pressurise. Think of a
opening a lemonade bottle. The
lemonade, under pressure, is able to
hold more dissolved carbon dioxide
which is released as bubbles when the
pressure drops. This is not only a good
illustration of how the properties of an
icompreesible liquid change with
pressure. It also shows rather
graphically what would happen to you
bloodstream and tissues should you
ascend too rapidly from depth.
||" you don't even need to breathe."
As has been already said, we all nead to
breathe. It's a fairly low brain function.
Some claim that it can be controlled,
but you'd probably have tobe a serious
yogic to do it. Let's put this down as a
||So why do I think this might work?
||Well, the external 'Lung Machine' has
been stated to be at atmospheric
pressure. This means that, if the
bloodstream contains gases excess to
atmospheric pressure, that they will
bubble off inside the machine, keeping
the gases disolved in the blood to
surface levels. Whether you would still
be able to use this amount when the
blood is repressurised remains to be
||There are a few difficilties glossed over,
||First, I have no idea if you'd be able to
use the smaller volume of gas now
found in the blood. When you breathe
under normal scuba conditions, the air
comes out of the second stage
regulator at (roughly) the pressure of
the surroundings. This feels normal and
I still breathe the same volume. I'm not
magically able to take smaller breaths
because there are more oxygen atoms
per unit volume, even though you might
logically think I'd be able to. With only
surface levels of air dissolved in the
bloodstream, you might not find
enough oxygen to survive.
||Secondly, Aq_Bi, you don't seem to
believe that liquids pressurise. That
means you probably think that you can
just run a tube into the box. This isn't
going to work as the blood would
transmit the pressure and the inside of
the box would find itself at surrounding
pressue. To maintain 1 atmosphere
inside the box you'd have to have
pressure valves on the inlet and outlet
(think little rotary airlocks, only for
blood), would have to pump the blood
in and out and run a vacuum pump to
keep the pressure in the vessel down.
||I'm changing my vote to neutral. There's
a lot of handwaving and (I think)
misunderstandings over the complexity
of the idea That and the central point of
whether you could survive at pressure
with only surface amounts of gases
disolved in your bloodstream gives me
cause for doubt. [~]
||Slightly off topic and something I probably shouldn't bring up as it plays a small role in a thing I am writing, but...
|| One: I wonder if it is within the realm of possibility to genetically engineer a human being to have no pores.
That person wouldn't be able to regulate their own body temperature but they also should be impermeable and not bloat in water.
||Two: Design a mechanical interface that would be attached to the infant umbilical-ly before birth and would regulate oxygen and other gasses in the blood so that the baby never takes its first breath. It would be born underwater and suffer none of the panic associated with not breathing because he/she never started doing so.
Through electrolysis, the interface would separate the surrounding water into hydrogen and oxygen. Screening the blood and extracting other gasses, the interface would keep the optimum amount of oxygen in the bloodstream for any given circumstance determined by heart rate.
After a few generations, as their lungs atrophied, their appendixes might actually reactivate to draw oxygen directly from the water. Sort of a forced devolution for colonizing aquatic worlds.
||Any input on this subject would be recieved gladly. It's kind of a hard subject to research.
||There's quite a debate, it seems, about the appendix. I had never heard what it was for and now my head hurts from reading some of the arguements about it.