In the movie The Abyss, SCUBA Divers are operating with experimental Liquid Breathing systems. There is one particular scene where Virgil "Bud" Brigman (played by Ed Harris) is gearing up for his first test with the Navy test equipment. Navy seal Ensign Monk fills up Bud's diving helmet with a colored fluorocarbon goo, and watches him frantically fighting the impulse not to breathe the liquid:
Relax, now, Bud. Don't hold your breath, take it in, just let yourself take it in. We all breathed liquid for 9 months, Bud, the body will remember

Bud is at the point of suffocating, when he inhales the liquid, floods his lungs, and starts breathing the liquid.

Sounds farfetched? Actually, the first experiments with liquid breathing systems were conducted in the mid 1960s. Researchers found that salt solutions could be saturated with high concentrations of dissolved oxygen at elevated pressures. These saturated solutions were fed to mice, that were kept alive up to 18 hours while breathing the saline solutions. Eventually, the mice did not die from oxygen deprivation, but from a buildup of carbon dioxide in their lungs.

Later research focused on the use of fluorocarbons (e.g. freon): chemically inert liquids that can contain high concentrations of dissolved oxygen and carbon dioxide. The problem with high (toxic) carbon dioxide concentrations remained, and this could only be solved by using an active recirculation system that fed fresh oxygenated liquid to the lungs, and stripped carbon dioxide from the exhaust stream. Using this system, larger animals (such as rats, and eventually dogs could be kept alive. This led the way to adapting the system for human applications.

So what is the purpose of these liquid breathing systems? As it is portrayed in The Abyss, liquid breathing may have a use in SCUBA diving at extreme depths. Oxygen becomes toxic at high pressures, and is therefore always mixed with an inert gas. Regular SCUBA diving to moderate depths is done with compressed air (mainly oxygen and nitrogen), but this becomes troublesome at higher depths due to the risks of nitrogen narcosis. At higher depths, mixtures of oxygen, helium (and a small amount of nitrogen) are used. This works well for depths up to approximately 200 meters (or 20 bar pressure). Higher depths are risky, if not impossible with SCUBA gear. Also, dissolved gases in the blood stream may cause big problems during the ascend (decompression sickness, "the bends"). A liquid breathing system could circumvent these problems, since the lungs are completely filled with an incompressible fluid, and you could dose the oxygen at a safe, low concentration without having to worry about additional inert gases entering the bloodstream. However, the problems with fluid recirculation and carbon dioxide buildup are still too complex to make this technology work.

Liquid breathing does have a current application in medical treatments. Alliance Pharmaceutical Corporation makes a perfluorooctyl bromide (perflubron), marketed under the name LiquiVent ®. This product is used for partial liquid ventilation. The fluid is administered to the lungs in conjunction with mechanical ventilation in patients with acute respiratory failure (caused by severe burns, infection, inhalation of toxic substances, or premature birth). The perflubron aids in opening the alveoli (air sacs) of the patients to facilitate the gas exchange in the lungs, and reduce the negative effects of mechanically assisted breathing. It can also wash out debris from the alveoli, deliver drugs to the lungs, function as an anti-inflammatory agent, and can be used as a contrast liquid for x-ray imaging.

Liquid Ventilation is the medical process of using a breathable liquid in order to help recovering damaged lungs or to support the life of a patient with a damaged respiratory system. Mostly used to support the lives of prematurely born infants, whose lungs were not fully developed. The liquid used in this operation is a perfluorocarbon (PFC).

In 1962, Dr. Kylstra who was a physiologist at the State University of New York (SUNY) at Buffalo, first evaluated the ability to sustain gas exchange in mice spontaneously breathing saline oxygenated at 6 atmospheres. Later in 1966, researches Leland C. Clark, Jr. and Frank Gollan discovered that there this could be an alternative method for supporting injured lungs. They found that mice can survive when submerged in perfluorocarbon under normobaric conditions for several hours. Since then, a great deal of research at many centers has focused on the use of liquid ventilation to assist respiration in patients with impaired pulmonary function.

Studies of total (tidal) liquid ventilation were first performed in treatments of several premature babies in 1989. These studies showed improvement in patients' lung compliance and gas exchange, but could not be pursued further due to the lack of technology to provide an applicable liquid ventilator system. Also at that time there was not a pharmaceutical-grade PFC available.

Illustration of using liquid ventilation in full-grown humans has been shown in movies such as The Abyss: Bud Brigman, the character portrayed by actor Ed Harris, uses a special diving suit filled with a breathable liquid. In Neon Genesis Evangelion, EVA's entry plug is filled with LCL which is also some kind of a breathable liquid.


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