Liquid fluorocarbons have a very high capacity for holding gas in solution. They can hold more oxygen or carbon dioxide than blood does. For that reason, they have attracted ongoing interest related to the possibility of artificial blood or of liquid breathing.
Blood substitutes are the subject of research because the demand for blood transfusions grows faster than donations. In some scenarios, artificial blood may be more convenient or safe. Because fluorocarbons do not normally mix with water, they must be mixed into emulsions (small droplets of perfluorocarbon suspended in water) in order to be used as blood. One such product, Oxycyte, has been through initial clinical trials.
Possible medical uses of liquid breathing (which uses pure perfluorocarbon liquid, not a water emulsion) involve assistance for premature babies or for burn patients (if normal lung function is compromised). Both partial and complete filling of the lungs have been considered, although only the former has undergone any significant tests in humans. Several animal tests have been performed and there have been some human partial liquid ventilation trials. One effort, by Alliance Pharmaceuticals, reached clinical trials but was abandoned because of insufficient advantage compared to other therapies.
Nanocrystals represent a possible method of delivering water- or fat-soluble drugs within a perfluorochemical fluid. The use of these particles is being developed to help treat babies with damaged lungs.
Perfluorocarbons are banned from sports, where they may be used to increase oxygen use for endurance athletes. One cyclist, Mauro Gianetti, was investigated after a near-fatality where PFC use was suspected. Other posited applications include deep-sea diving and space travel, applications that both require total, not partial, liquid ventilation. The 1989 film The Abyss depicted a fictional use of perfluorocarbon for human diving but also filmed a real rat surviving while cooled and immersed in perfluorocarbon. (See also list of fictional treatments of perfluorocarbon breathing.)