Effects of environmental tobacco smoke on eustachian tube surfactant in guinea-pigs

Abstract

Cigarette smoking has been shown to reduce the amount of pulmonary surfactant and thus damage pulmonary function (Higenbottam, 1985;Mancini et al., 1993). Surface tension-lowering substances are also present in the eustachian tube in canines, rodents and humans. The major function of the eustachian tube is to equalize pressure between the middle ear and the external atmosphere, and surface tension-lowering substances present in the middle-ear cleft facilitate the opening of the eustachian tube. Evidence from studies in experimental animals suggests that substances which lower the surface tension facilitate the opening of the eustachian tube and also allow effective mucociliary clearance (Birken & Brookler, 1972; Jiang & Guo, 1992). It has thus been suggested that a deficiency of auditory surfactant could cause failure of eustachian tube opening and make the ear more susceptible to secretory otitis media. Studies in experimental animals confirmed that the pressure necessary for opening the eustachian tube was increased when effusion was present in the middle ear but was significantly reduced after treatment with artificial surfactant (Kodama & Asakura, 1993). A clinical study showed that clinical symptoms, signs and test results in otorhinolaryngology were improved when adults and children were treated with drugs that facilitated the synthesis of surfactant, with a significant difference between the treated and control groups (Passali & Zavattini, 1987). These results suggest that eustachian tube surfactant plays an important role in its physiological function.