Change of middle ear transfer function in otitis media with effusion model of guinea pigs.

Otitis media with effusion (OME) is an inflammatory disease of the middle ear that causes most cases of conductive hearing loss observed in the pediatric population. With the long term goal of evaluating middle ear function with OME, the aim of the current study was to create an animal model of OME in which middle ear transfer functions could be measured. In guinea pigs, OME was created by injecting lipopolysaccharide (LPS) into the middle ear. Evidence of OME was assessed by otoscopy, tympanometry, histology, and by measuring the volume of fluid in the middle ear. Vibrations of the umbo and round window membrane were measured with a laser Doppler vibrometer at frequency range of 200-40 kHz in three groups of 3, 7, and 14 days after injection of LPS. Changes in displacement of the umbo and round window membrane in response to 80 dB SPL sound in the ear canal were measured across the frequency range. Displacement of both the umbo and round window membrane was reduced at all time points following LPS injections. Further, the change of the displacement transmission ratio (DTR) from the tympanic membrane to the round window occurred mainly in chronic (e.g. 14 days post-LPS injection) OME ears. This study provides useful data for analyzing the change of middle ear transfer function in OME ears.