The concept of liquid respiration was first proposed in 1962, when Kylstra (1) and others found that rats could breathe freely in saline at 6 atmospheres and survive for several hours. In 1965, Clark et al. found that rats could breathe freely in a fluorocarbon liquid (Fluorocarbon) - FC75 under a large pressure of oxygen and survived well.(2) This discovery enabled the concept of liquid respiration to be realized, and in recent years, many researchers have been using fluorocarbons in liquid respiration research. respiratory research.
Perfluorochemicals(3)
The molecular structure of these compounds is similar to that of carbohydrates, and if the water molecules connected to the carbon atoms in carbohydrates are replaced by fluorine atoms, they can produce perfluorocarbons, which are collectively known as perfluorinated compounds (PFCs). These compounds are collectively called Perfluorochemicals (hereafter referred to as PFCs).
PFC is a colorless, odorless, non-toxic liquid, insoluble in water or fat, and its solubility in oxygen is 20 times that of water. The solubility of carbon dioxide is three times that of water. the surface tension of PFC is very low, and PFC is currently used as a liquid respiratory surgery PFC evaporates faster than water at body temperature, Table 1 is a number of more commonly used as a liquid respiratory surgery of the characteristics of PFC (3).
The metabolism of PFCs is primarily volatilized by the lungs; only a very small amount is absorbed by the lungs, and after absorption, the PFCs are carried through the membranes of fat-containing cells to the liver, spleen, or other fat-containing cells. These PFCs will return to the circulatory system, and almost all volatilized by the lungs, only a very small amount will be excreted by the skin. PFCs are extremely biologically inert, will not be converted into other substances or metabolized, and therefore are very safe. Current biomedical uses of PFCs include contrast agents, plasma substitutes and eye crystal substitutes. Therefore the safety of use in liquid apheresis should be assured.
Histologic examination has revealed less lung injury (including reduced formation of vitelliform lesions, reduced injury to respiratory epidermal cells and terminal alveoli, and higher alveolar debris clearance) in preterm animals treated with liquid apnea (3-5). A prolonged study in monkeys also found that lung function remained normal 3 years after the use of liquid apnea (6).