Liquid breathing can not effectively protect the lung from biophysical forces associated with the gas ventilator. New application modes for PFC have been developed. Partial liquid ventilation (PLV) involves filling the lungs with a fluid. This fluid is perfluorocarbon, also called Liquivent or Perflubron. The liquid has some unique properties. It has a very low surface tension, similar to surfactant, a substance that is produced in the lungs to prevent the alveoli from collapsing and sticking together during exhalation. It also has a high density, oxygen readily diffuses through it, and it may have some anti-inflammatory properties. In PLV, the lungs are
Liquid as a linear medium, so that sound propagates without dissipation and without mode coupling. In reality, any liquid shows some dispersion: with increasing frequency, "K" crosses over from the low-frequency, liquid-like limit formula_6 to the high-frequency, solid-like limit formula_7. In normal liquids, most of this cross over takes place at frequencies between GHz and THz, sometimes called hypersound. At sub-GHz frequencies, a normal liquid cannot sustain shear waves: the zero-frequency limit of the shear modulus is formula_8. This is sometimes seen as the defining property of a liquid. However, just as the bulk modulus "K", the shear modulus "G" is