gms | German Medical Science

“System4” is a new Nucleus system which, besides other advantages, enables higher stimulation rates to be used than in the previous device. With the new system it is possible to utilize the ACE speech processing scheme at much higher rates than the previously used rate of 1200 pulses per second (pps) - in this study up to 3500 pps per channel.

In a prospective clinical study 18 subjects were implanted with the “system4” in Hannover. While our primary goal was to evaluate the new NRT measurement system, we also investigated the impact of rate on speech perception. Three different rates were tested, using ACE speech processor programs of 500 pps (A), 1200 pps (B) and 3500 pps (C). For speech perception testing we chose the Freiburger Monosyllabic Word test in quiet and the Oldenburger Sentence test in noise (OLSA). To avoid learning effects, the speech trial did not start until subjects had used their devices for at least 3 months; it was performed in an ABC-CBA cycle with each condition used for a duration of around 4 weeks. At the end of the cycle each subject compared all 3 programs over a 2-week period and was asked for her/his subjective preference.

To date 6 subjects have completed the trial. The individual results are very encouraging: the mean score in the Freiburger Monosyllabic Word test is 61% (median 65%); the mean signal-to-noise ratio for 50% correct understanding in the OLSA test in noise is 0 dB (median 1 dB). The outcome with regard to rate preference is also very interesting: each of the three conditions was favored by 2 subjects.

At present it is too early to discuss these results in detail. We require more data in order to draw further conclusions. However, these preliminary data already indicate that the fastest rate is not always the preferred rate.