Real ear to coupler differences in children having otitis media with effusion

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Abstract
The aim of this study was to investigate the effects of otitis media with effusion (OME) on the 'real ear to coupler difference' (RECD) in children. RECDs are important in the procedures used for selection of appropriate amplification characteristics for children with permanent (usually sensorineural) hearing impairment. Subjects were 28 children aged between 4.6 and 7.6 years, 14 of whom had OME. There was no evidence of middle ear pathology in the remaining 14 who comprised the control group. All real-ear and coupler measures showed good test-retest repeatability at 4.0 kHz and below. The mean RECDs in frequency range 0.2-3.0 kHz were found to be up to 3.5 dB greater for the children having OME than for those without OME, although when statistically analysed only the differences in RECD at 1.0 kHz and 1.5 kHz were significant. Due to low correlation between the root mean square (RMS) sound pressure level (SPL) in the ear canal and ear canal volume, and low correlation between the subject's maximum RECD and ear canal volume, neither of these other variables could be used to predict an individual's RECD in this study. Large inter-subject variability was found, with a maximum standard deviation of 5.6 dB at 0.2 kHz, so this study greatly supports the need for individual RECD measurements to be made whenever possible, rather than using averaged transformation figures, particularly if the individual has OME.