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.