| SUBMAN1 |
03-27-08 03:31 PM |
Wikipedia, though a terrible source for inaccurate information sometimes (Or should I say, mis-information), has some info on it I found:
http://en.wikipedia.org/wiki/Liquid_breathing
-S
Quote:
Liquid breathing
Liquid breathing is a form of respiration in which a normally air-breathing organism breathes an oxygen-rich liquid (usually a perfluorocarbon), rather than breathing air. It is used for medical treatment and could some day find use in deep diving and space travel. Liquid breathing is sometimes called fluid breathing, but this can be confusing because both liquids and gases can be called fluids.
Diving
In diving, the pressure inside the lungs must effectively equal the pressure outside the body, otherwise the lungs collapse. Mathematically speaking, if the diver is f feet (or m meters) deep, and the air pressure at the water surface is p bar (usually p = 1, but less at high-altitude lakes such as Lake Titicaca), he must breathe fluid at a pressure of f/33+p = m/10+p bar.
Since external and internal pressures must be equal, the required gas pressure increases with depth to match the increased external water pressure, rising to around 13 bar at 400 feet (120m), and around 500 bar on the oceans' abyssal plains. These high pressures may have adverse effects on the body, especially when quickly released (as in a too-rapid return to the surface), including air emboli and decompression sickness (colloquially known as "the bends"). (Diving mammals, as well as free-diving humans who dive to great depths on a single breath, have little or no problem with decompression sickness despite their rapid return to the surface, since a single breath of gas does not contain enough total nitrogen to cause tissue bubbles on decompression. In very deep-diving mammals and deep free-diving humans, the lungs almost completely collapse).
One solution is a rigid articulated diving suit, but these are bulky and clumsy. A more moderate option to deal with narcosis is to breathe heliox or trimix, in which some or all of the nitrogen is replaced by helium. However, this option does not deal with the problem of bubbles and decompression sickness, because helium dissolves in tissues and causes bubbles when pressures are released, just like nitrogen does.
Liquid breathing provides a third option. With liquid in the lungs, the pressure within the diver's lungs could accommodate changes in the pressure of the surrounding water without the huge gas partial pressure exposures required when the lungs are filled with gas. Liquid breathing would not result in the saturation of body tissues with high pressure nitrogen or helium that occurs with the use of non-liquids, thus would reduce or remove the need for slow decompression. (This technology was dramatized in James Cameron's 1989 film The Abyss.)
A significant problem, however, arises from the high viscosity of the liquid and the corresponding reduction in its ability to remove CO2. All uses of liquid breathing for diving must involve total liquid ventilation (see above). Total liquid ventilation, however, has difficulty moving enough liquid to carry away CO2, because no matter how great the total pressure is, the amount of partial CO2 gas pressure available to dissolve CO2 into the breathing liquid can never be much more than the pressure at which CO2 exists in the blood (about 40 mm of mercury (Torr)).
At these pressures, most fluorocarbon liquids require about 70 mL/kg minute-ventilation volumes of liquid (about 5 L/min for a 70 kg adult) to remove enough CO2 for normal resting metabolism.[10] This is a great deal of fluid to move, particularly as liquids are generally more viscous than gases, (for example water is about 56 times the viscosity of air). Any increase in the diver's metabolic activity also increases CO2 production and the breathing rate, which is already at the limits of realistic flow rates in liquid breathing.[11][12] It seems unlikely that a person would move 10 liters/min of fluorocarbon liquid without assistance from a mechanical ventilator, so "free breathing" may be unlikely.
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Now this is interesting:
Quote:
The movie The Abyss also features a scene with a rat submerged in and breathing fluorocarbon liquid, filmed in real life.
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