Functional effects of repeated pressure loads upon the tympanic membrane: mechanical stiffness measurements after simulated habitual sniffing.

In experimental studies it was found that otitis media causes stiffness loss in the tympanic membrane, possible precursors to retraction pockets and cholesteatoma. Besides otitis media habitual sniffing behaviour is associated with the development of retractions. The present study aims to test the hypothesis that repeated sniffing manoeuvre may cause not only structural, epithelial tympanic membrane changes presumed to be possible precursors to retractions, but also tympanic membrane stiffness loss, another possible mediator for the development of retractions. An experimental model with a pressure chamber was used to mimic the pressure conditions for the tympanic membrane in habitual sniffers' ears. The stiffness properties of twelve Mongolian gerbil tympanic membranes were measured with moiré interferometry after varying time up to 12 days with repeated pressure loading. Three days later, lower overall displacement were obtained in two ears; after 7-12 days the displacement readings were normal. This study with maximum of 12 days of pressure loading did not verify the hypothesis that habitual "sniffing" impairs the stiffness of the tympanic membrane.