Multicentre clinical trial shows benefits of Crystalis^XDP

Bozorg-Grayeli and colleagues from five different university hospitals in France¹ showed that Oticon Medical cochlear implant users (20 adults) benefited from a sound processor upgrade introducing Crystalis^XDP.
Improvements were observed in speech perception scores in quiet at different intensities, in speech perception in noise, and in a global improvement in sound quality. In particular, when compared to the former signal processing strategy, speech perception in noise had improved by 30–40% after a 30-day habituation period. 
Speech recognition was first assessed in quiet at 40, 55, 70 and 85 dB SPL. Crystalis^XDP was set to its medium preset, optimised for sounds with an average intensity of 70 dB SPL. As seen in Figure 1, all scores were higher with Crystalis^XDP, either on the day of renewal or after the habituation period had ended. Scores gradually increased for speech sounds presented at 55 dB SPL, reaching a significant +8.5% compared to the standard strategy after the habituation period. Improvements were also observed for higher intensities, with +7.8% at 70 dB SPL (significant at Day 0), and a +17.7% at 85 dB SPL at Day 30, suggesting a better representation of loud sounds.

Figure 1: Vocal audiometry in quiet at 40, 55, 70 and 85 dB (n = 20)

Speech-in-noise perception was assessed by presenting isolated words together with noise from a cocktail party, at a signal-to-noise ratio (SNR) of +10 dB. Group results showed that scores increased from the standard strategy (27.5%) to Crystalis^XDP (32.7%) on Day 0 and on Day 30 (54.6%), leading to an average improvement of +27.1% improvement for the 20 participants after the habituation period. 
To verify that this effect was really due to the change in signal processing strategy and other factors present during the habituation period, the authors obtained supplementary data on Day 30 for the standard strategy on nine participants (Figure 2). Within this subgroup, speech-in-noise performance appeared to already be better on Day 0 with Crystalis^XDP than with standard, with a +10.4 % advantage for Crystalis^XDP; these findings became statistically significant after the habituation period and culminated with a +40% improvement for speech perception in noise compared to the standard strategy.

Figure 2. Vocal audiometry in noise (10-dB SNR cocktail party noise, n = 9) 

As shown in Figure 3, all subjective sound quality ratings where higher with Crystalis^XDP, with a statistically significant change in main effect of strategy. Marked differences (*significant differences after planned comparisons) were observed in the pooled items: Noise: Speech intelligibility, sound quality in noise, subjective listening effort and social interaction; Leisure: TV, music and telephone. These results demonstrate that a signal processing strategy optimised for speech perception and associating a wide input dynamic range to a back-end multi-channel compression system like Crystalis^XDP can improve speech perception and overall satisfaction in cochlear implant users. 

Figure 3. Subjective sound quality appraisal (score out of 10)