Fluid breathing

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Liquid breathing is an experimental procedure in diving technology and diving medicine , in which the gas exchange in the lungs does not take place via air or a breathing gas mixture , but via a liquid enriched with oxygen . In the simplest case, the liquid would be inhaled and exhaled like air, but this is not easily possible because of the considerably higher breathing resistance and other problems.

Liquid breathing and diving technique

Successful use of laboratory-only-proven liquid breathing would solve some of the problems encountered in deep diving:

  • A decompression in today's scale would not be necessary, it would be easier for the time used smaller. A saturation of inert gases in the tissue would largely be eliminated, the gas exchange in the lungs is limited to the exchange of carbon dioxide and oxygen .
  • The complex use of a breathing gas mixture including inert gas (e.g. helium) is no longer necessary, and complex gas changes are largely eliminated.
  • Pressure control technology to compensate for the changing water pressure, as it exists today in regulators , would not be necessary or would look completely different. The volume of the fluid-filled lung is independent of the depth due to the incompressible fluid.

There are some striking disadvantages to be mentioned. Some technical problems and biological issues have not yet been resolved or not fully resolved. The (more) technical questions include:

  • High breathing resistance of the liquid. To overcome this, technical help such as forced ventilation would probably be necessary in diving practice.
  • The question of pendulum breathing in liquids, especially the circulation within the lungs down to the alveoli
  • Cooling down or overheating of the diver through the breathing fluid
  • Communication without usable vocal cords
  • (Clear) vision when the diving mask is flooded and the direct effect of the liquid on the eyes
  • Pressure equalization in the middle ear
  • Safe and biologically compatible switch from gas breathing to liquid breathing and back
  • The not yet developed technical diving apparatus including liquid treatment, reserve and redundancy as well as the guarantee of sterility, safety and energy supply. The immersion apparatus would also have to ensure liquid circulation and temperature control.

For very deep dives, there are other factors to consider:

  • Possible toxicity of oxygen at extremely high partial pressures
  • Possible direct neurological damage from the pressure on extremely deep dives. In the case of laboratory animals, this could in part be combated with the administration of anesthetics before the dive.
  • Possible cell damage from high pressures

An application in diving is currently ruled out because of the still unsolved problems. The means for the technical diving handling of liquid treatment, carbon dioxide separation or oxygen enrichment have not yet been developed.

Experiments and history

Johannes A. Kylstra ( Leiden , Holland) tested liquid breathing on a small scale in the 1970s and 1980s. He later continued his research at the University of Buffalo, New York . Further results come from Leland Clark and Golan. The research was later carried on by the National Advisory Committee for Aeronautics (NACA).

The method has been successfully tested on laboratory animals, for example rats. Gradually, the survival of the test animals could be ensured. Human, partial fluid respiration through a lung was also successfully tested. Oxygen-enriched fluorocarbons were used .

Existing biological problems

The unsolved or only partially resolved biological questions include:

  • Lung damage in laboratory animals,
  • further lung damage in animals, caused mechanically by ventilation
  • the removal of CO 2 from the lungs through the fluid
  • the temperature dependence of the CO 2 evacuation in the lungs
  • the possible accumulation of respiratory fluid in the blood
  • the hazard-free and biologically compatible switch from liquid breathing to gas breathing and back
  • realistic and observed damage to the body and lungs in the case of contaminated respiratory fluid

Use in medicine

A modification or secondary development, fluid ventilation, is used in the medical field to treat lung damage (fumes, babies, infections).

The liquid, enriched with oxygen and carbon dioxide, supports the gas exchange and, if successful, opens collapsed alveoli or prevents their collapse. Since perfluorocarbon (PFC) is twice as heavy as water, it can even expand a collapsed lung and thus prepare for better gas exchange. This takes place in sedation so that the liquid cannot be exhaled during independent breathing movements. The mechanical stress on the lungs is often lower than with a ventilator , and secondary damage can be reduced under certain circumstances.

The treatment is still being tested, but has now apparently reached a safe level.

In addition to the described liquid breathing (TLV), the inhalation of the liquid (PFC vapor or aerosol PFC) as well as pendulum breathing with liquid and gas (PLV) are being discussed in the medical sector and tested on animals.

Liquids used

The liquids used in the medical field and in laboratory experiments are, in addition to saline water (isotonic, 0.89% saline solution ), mostly fluorocarbons (fluorocarbons, English fluorocarbon or perfluorocarbon), for example LiquiVent from Alliance, perfluorooctyl bromide, with the formula C 8 F 17 Br.

Cultural references

In the movie Abyss by James Cameron , the use of a liquid diving suit by the main actor Ed Harris is shown with some of the mentioned problems. In spite of the fictitious diving technique shown, actual human fluid breathing does not take place, it is merely a filmic representation. The laboratory rat also shown in the film, however, is not a trick, it breathes real liquid.

Ben Bova describes another application of a breathable liquid in his novel Jupiter from the Grand Tour series. There a mission into Jupiter's atmosphere and even its fictional global ocean is described. It would be much more complex to construct a manned vehicle so stable that it could withstand the extreme pressure difference with the corresponding size. Another problem would be to let it rise again from the giant planet's deep gravitational potential with the total mass required for this. Interestingly enough, there are critics of the book who reject this breathing technique as being completely illusory.

In order to withstand the high acceleration during rocket launch, liquid-filled chambers have been proposed for spaceships. The astronauts would have to breathe liquid in these chambers. The chambers were fictitiously used in the youth book series by or about Mark Brandis , as special suits in the television series UFO (1969/70), in the closing sequence of Brian De Palma's Mission to Mars (2000), as acceleration tanks in Joe Haldeman's novel The Eternal War or as an energetic stasis field with Roger Leloup and Luc Orient's Terango-Reisen. The transition from gas breathing to liquid breathing can be found, for example, in Flash Gordon .

Because the medically used LiquiVent has a density of 1.93 g / ml, it would be less suitable for high accelerations than the isotonic saline solution, which is much closer to human tissue in its density. The lower solubility of oxygen in the isotonic saline solution compared to the LiquiVent could be countered by increasing the partial pressure of the oxygen.

Science fiction literature