[2] Thus, it is critical to choose the appropriate PFC for a specific biomedical application, such as liquid ventilation, drug delivery or blood substitutes.

[3] In theory, liquid breathing could assist in the treatment of patients with severe pulmonary or cardiac trauma, especially in pediatric cases.[how?]

Although total liquid ventilation (TLV) with completely liquid-filled lungs can be beneficial,[9] the complex liquid-filled tube system required is a disadvantage compared to gas ventilation—the system must incorporate a membrane oxygenator, heater, and pumps to deliver to, and remove from the lungs tidal volume aliquots of conditioned perfluorocarbon (PFC).

Many prototypes are used for animal experimentation, but experts recommend continued development of a liquid ventilator toward clinical applications.

It has a very low surface tension, similar to the surfactant substances produced in the lungs to prevent the alveoli from collapsing and sticking together during exhalation.

The study of PLV involves comparison to protocolized ventilator strategy designed to minimize lung damage.

With aerosolized perfluorooctane, significant improvement of oxygenation and pulmonary mechanics was shown in adult sheep with oleic acid-induced lung injury.

[23][24][25] The first medical use of liquid breathing was treatment of premature babies[26][27][28][29] and adults with acute respiratory distress syndrome (ARDS) in the 1990s.

Liquid breathing was used in clinical trials after the development by Alliance Pharmaceuticals of the fluorochemical perfluorooctyl bromide, or perflubron for short.

Furthermore, perfluorocarbons have been demonstrated to reduce lung inflammation,[30][31][32] improve ventilation-perfusion mismatch and to provide a novel route for the pulmonary administration of drugs.

The second image shows experimental results comparing both plasma and tissue levels of gentamicin after an intratracheal (IT) and intravenous (IV) dose of 5 mg/kg in a newborn lamb during gas ventilation.

[43] The technology came to be called gas/liquid ventilation (GLV), and was shown able to achieve a cooling rate of 0.5 °C per minute in large animals.

[45] The nasopharyngeal (NP) approach is unique for brain cooling due to anatomic proximity to the cerebral circulation and arteries.

Special breathing gas mixes such as trimix or heliox reduce the risk of nitrogen narcosis but do not eliminate it.

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.

[51] This is a great deal of fluid to move, particularly as liquids are more viscous and denser than gases, (for example water is about 850 times the density of air[52]).

However, it has been suggested that a liquid breathing system could be combined with a CO2 scrubber connected to the diver's blood supply; a US patent has been filed for such a method.

As liquids cannot be practically compressed, they do not change density under high acceleration such as performed in aerial maneuvers or space travel.

A person immersed in a liquid of the same density as tissue has acceleration forces distributed around the body, rather than applied at a single point such as a seat or harness straps.