Objectives: The present study examined the effect of pulse phase duration on electrically evoked compound action potentials (eCAP) measurability, thresholds, and their relationship with behavioral comfort levels on implant models with default pulse phase duration of 37 µs. Study design: Within-subject comparison of prospectively collected clinical data. Setting: Large cochlear implant (CI) program at government funded academic and research institute. Patients: Prelingually deafened paediatric unilateral CI users using Cochlear Nucleus CI422 implant with slim-straight electrode array (n = 62). Main outcome measures: eCAPs were recorded across 5 electrodes across the array (E01, E06, E11, E16, and E22) in 62 paediatric CI422 users using 25 µs (via AutoNRT) and 37 µs (via advanced-NRT) durations. Results: The χ 2 test revealed significantly higher eCAP measurability with 37 µs than with 25 µs pulse phase duration. The 37 µs eCAP thresholds fell within 62% to 73% of the electrical dynamic range, whereas the 25 µs thresholds exceeded it (105% to 117%). A moderate positive correlation (r = 0.40 to 0.6) was found between eCAP thresholds and behavioral comfort levels for both pulse phase durations. The comparison of eCAP thresholds in terms of clinical units (CL) revealed significantly lower eCAP thresholds with 37 µs pulse phase duration ( P 0.05). Conclusion: eCAP measurements with 37 µs pulse phase duration can maximize eCAP recordings, especially for Cochlear Nucleus implants with slim-straight electrode arrays.
Saravanan et al. (Mon,) studied this question.
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