gms | German Medical Science

To develop guidelines for using Compound Action Potential (eCAP) and Stapedius Reflex Threshold (eSRT) measurements to optimise High Resolution fitting and hence user benefit, by investigating the relationship between these objective measures and psychophysical data.

Subjects from 15 European centres are included. All are unilateral CII-Bionic Ear^® or HiRes90K^TM users. The eCAP was measured through Neural Response Imaging (NRI), with the SoundWave^® fitting software, on stimulating/recording pairs 3/1, 7/5, 11/9, and 15/13. Measurements were performed intra-operatively, at first fitting, and after three, six and twelve months of device use. Visually observed eSRT measurements were made intra-operatively, using SoundWave^® speech bursts. Subjects were fitted using the SoundWave® default parameters i.e. speech bursts and automatic calculation of thresholds (Ts): 10% of most comfortable levels (Ms).

Data from 40 subjects have been collected at various stages of implant use. Preliminary trends involving NRI thresholds (tNRI), eSRT and Ms will be presented. Results show that first fitting Ms are 50% of intra-operative tNRI; stable Ms (more than three months of implant use) are equal to 80% of intra-operative tNRI. The eSRTs appear to be correlated to stable M levels.

The above results indicate that NRI and eSRT appear promising for prediction or verification of program levels from a reasonably sized study group. Data collection is ongoing with at least 80 data sets expected. The next step is to compare NRI and/or eSRT based program outcomes, to programs based on behavioural fitting methods.