A synthetic emulsion reproduces the functional properties of pulmonary surfactant.

An effective substitute for pulmonary surfactant must be able to reduce water-vapour surface tensions to under 1 mN/m and it must spread rapidly and spontaneously at the air interface from the aqueous phase. Pure dipalmitoylphosphatidylcholine meets the former requirement, but not the latter. A synthetic surfactant is described which meets both of these criteria. The surfactant is prepared as a DPPC monolayer stabilizing an aqueous emulsion of an inert fluorocarbon oil; it spreads rapidly at the air/liquid interface, lowers the surface tension to under 1 mN/m during compression at the air/liquid interface and restores normal pressure-volume characteristics to surfactant-depleted lungs.