title: Population-based prediction of fitting levels for individual cochlear implant recipients.
abstract: OBJECTIVE
  This study analyzed the predictability of fitting levels for cochlear implant recipients based on a review of the clinical levels of the recipients.
  
  
  METHODS
  Data containing threshold levels (T-levels) and maximum comfort levels (M-levels) for 151 adult subjects using a CII/HiRes 90K cochlear implant with a HiFocus 1/1 J electrode were used. The 10th, 25th, 50th, 75th and 90th percentiles of the T- and M-levels are reported. Speech perception of the subjects, using a HiRes speech coding strategy, was measured during routine clinical follow-up.
  
  
  RESULTS
  T-levels for most subjects were between 20 and 35% of their M-levels and were rarely (<1/50) below 10% of the M-levels. Furthermore, both T- and M-levels showed an increase over the first year of follow-up. Interestingly, levels expressed in linear charge units showed a clear increase in dynamic range (DR) over 1 year (29.8 CU; SD 73.0), whereas the DR expressed in decibels remained stable. T-level and DR were the only fitting parameters for which a significant correlation with speech perception (r = 0.34, p < 0.01, and r = 0.33, p < 0.01, respectively) could be demonstrated. Additionally, analysis showed that T- and M-level profiles expressed in decibels were independent of the subjects' across-site mean levels. Using mixed linear models, predictive models were obtained for the T- and M-levels of all separate electrode contacts.
  
  
  CONCLUSIONS
  On the basis of the data set from 151 subjects, clinically applicable predictive models for T- and M-levels have been obtained. Based on one psychophysical measurement and a population-based T- or M-level profile, individual recipients' T- and M-levels can be approximated with a closed-set formula. Additionally, the analyzed fitting level data can serve as a reference for future patients.
authors.affiliation: Department of Otolaryngology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Feddo B
authors.initials: FB
authors.lastname: van der Beek
authors.forename: Jeroen J
authors.initials: JJ
authors.lastname: Briaire
authors.forename: Johan H M
authors.initials: JH
authors.lastname: Frijns
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001309:Auditory Threshold / Q000502:physiology*; D019929:Cochlear Implantation / Q000379:methods*; D003054:Cochlear Implants; D003638:Deafness / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D013067:Speech Perception / Q000502:physiology*; D055815:Young Adult