Beta-agonists and surfactant in eustachian tube function.

The presence of surface tension lowering substances (surfactants) is demonstrable in the Eustachian tube (ET) and the middle ear, both in animals and in humans. In the lungs, beta-adrenoceptor agonists stimulate the secretion of surfactant; and it has been suggested that beta-agonists have a similar effect both in the ET and the middle ear, because opening of the ET is facilitated by the non-selective beta-agonist, isoprenaline in the rat, and by the beta 2-agonist, terbutaline, in humans. Two studies are described: In one, children with otitis media with effusion took terbutaline or placebo twice a day for two weeks and no significant differences were found between the effects of the two treatments; in the other study, it was shown that surfactant markedly facilitated the opening of the Eustachian tube. Lung surfactant prepared from pigs and instilled as a single dose into the middle ear of healthy rats reduced the air pressure necessary to open the Eustachian tube by as much as 15-20% for as long as the experiments lasted (i.e., around one hour). Thus, possibilities of facilitating the opening of the Eustachian tube do in fact exist.