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Artificial SCUBA lung

It's a no-breather
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(+3, -5)
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against]

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.

Aq_Bi, Oct 10 2006

Free divers and the bends http://answers.yaho...060915203853AAXM7Lj
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]

Breathing Liquid http://en.wikipedia...ki/Liquid_breathing
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]

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       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.
Custardguts, Oct 10 2006
  

       What Custard said.   

       [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.]
st3f, Oct 10 2006
  

       It wouldn't prevent narcosis, either.
Shz, Oct 10 2006
  

       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.
webfishrune, Oct 11 2006
  

       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.)
DrCurry, Oct 11 2006
  

       //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.
Aq_Bi, Oct 12 2006
  

       OK... I've thought about it and I'm reversing my opinion. With that, comes a price. I'm going to point out what I think is wrong.   

       "Liquids are incompressible. If the blood pressure changed to match the depth pressure, it would kill you very fast."
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 maybe.
  

       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 seen.   

       There are a few difficilties glossed over, too:   

       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. [~]
st3f, Oct 12 2006
  

       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.
Zimmy, Oct 13 2006
  


 

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