Liquid ventilation

To live we need to breathe. Prior to being born we carry this activity out through the placenta and subsequently by means of our lungs. In normal development, the lungs of the foetus are filled with amniotic liquid and, on being born, the first cry activates this respiration surface. But the main problem that premature babies have is that their lungs are not well formed. Moreover, they often lack surfactant, a compound formed by proteins and lipids that avoids the lungs folding in on themselves before the baby gets stronger.

The respirators usually employd in these cases provide artificial surfactant, but not always in sufficient amounts to provide correct therapy. In order to alleviate this situation, the Nautical School at the University of the Basque Country has developed a liquid respiration respirator.

The machine simulates placentary respiration by filling the lungs of the premature baby with liquid and then the respirator introduces and extracts the required quantity of liquid at a suitable respiratory rhythm. The amount of liquid administered is usually in the order of 10 millilitres per kilogram of the baby’s weight.

Perfluorocarbons instead of air

Perfluorocarbon is used in liquid respiration, as it has a suitable surface tension in order to maintain the pulmonary structure and the fluorine has good properties for the transport of and interchange between blood and the gases, O2 and CO2. The respirator syringes introduce the oxygenated perfluorocarbon to the very last alveola. Here oxygen is released and carbon dioxide taken up in the same way as on the respiration surface. Then the respirator extracts part of the perfluorocarbon from the lungs and introduces the next oxygenated dose. The same machine carries out the removal of CO2 from the perfluorocarbon and adds oxygen to it.

Being full of liquid, the problems of pressure associated with conventional assisted respiration are avoided because the lungs of the premature baby suffer less stress and respire more easily.

However, this story does not have a happy ending. The respirator, for the moment, is no more than a prototype. In the experiments carried out at the Cruces hospital in Bilbao with artificial lungs and with animals, the results have been very good. It has even been applied successfully in more than 80 death-threatening situations in premature babies. But the perfluorocarbon for medical use is not available on the market. As premature babies need very small quantities and no commercial application for adults has been found, the patent-owning company has opted not to market it arguing that it lacks profitability. Thus, an industrial version of the liquid respirator is yet to be developed.