Optimizing the efficiency of ECAP measurements due to interpolation.

BACKGROUND: Thresholds of electrically evoked compound action potentials (TECAP) may serve as starting points for electrophysiologically based fitting of cochlear implants. Absent TECAP data at single electrodes reduces the number of data points available for fitting and can be substituted by interpolation of measured data points.

AIM: To compare complete TECAP profiles with interpolated TECAP profiles of 5/22 (∼22.7%) and 11/22 (50%) electrode contacts.

MATERIAL AND METHODS: Single-centre, retrospective, observational study of data from 624 ears implanted with a Slim Modiolar (CI ×32) or Contour Advance (CI ×12, CI24RE(CA)) electrode array (Cochlear Ltd). The deviation of the complete measured TECAP profile from the same profile with missing and therefore interpolated TECAP values was quantified.

RESULTS: Interpolated TECAP profiles significantly differ from complete measured profiles especially at the basal and apical electrodes. Reference data for Slim Modiolar and Contour Advance electrodes mean profiles are provided.

CONCLUSIONS AND SIGNIFICANCE: Reducing the number of measured TECAP electrodes has to be weighted against losses in the TECAP accuracy of interpolated values. A clinically acceptable compromise may be a reduction from 22 to 11 even non-equidistant data points. While reducing ECAP measurement time, it is accompanied by a minimal loss of accuracy of the TECAP threshold profile.