Investigations into electrically evoked stapedius reflex measures and subjective loudness percepts in the MED-EL COMBI 40+ cochlear implant.

For several years there has been interest in using objective measures to set channel-specific upper programming limits when programming the speech processor of cochlear implant users. The present study aims to add to previous reports by examining correlations between electrically evoked stapedius reflex threshold (ESRT) and a range of psychophysical loudness estimates in a group of 22 adult users of the MED-EL COMBI 40+ system. Thirteen of the 15 subjects (87%) had recordable stapedius reflexes. Psychophysical measures of threshold, maximum comfort level (MCL) and maximum acceptable loudness (MAL) were recorded. Results showed that mean ESRT was closest to the MCL using 500 ms burst ('MCL500'), with MCL50 (MCL using 50 ms burst) and MAL500 some 2dB and MAL50 3dB higher. Correlations between ESRT and the behavioural loudness judgements were highest for MCL500 (R = 0.69, p < 0.001) and slightly less for MAL500. These results confirm the ease of measuring ESRT in a clinical setting and that a high level of confidence can be placed on the use of these measures for setting processor maps in the absence of behavioural data.