title: Accuracy of measurement in electrically evoked compound action potentials.
abstract: BACKGROUND
  Electrically evoked compound action potentials (ECAP) in cochlear implant (CI) patients are characterized by the amplitude of the N1P1 complex. The measurement of evoked potentials yields a combination of the measured signal with various noise components but for ECAP procedures performed in the clinical routine, only the averaged curve is accessible. To date no detailed analysis of error dimension has been published. The aim of this study was to determine the error of the N1P1 amplitude and to determine the factors that impact the outcome.
  
  
  METHODS
  Measurements were performed on 32 CI patients with either CI24RE (CA) or CI512 implants using the Software Custom Sound EP (Cochlear). N1P1 error approximation of non-averaged raw data consisting of recorded single-sweeps was compared to methods of error approximation based on mean curves.
  
  
  RESULTS
  The error approximation of the N1P1 amplitude using averaged data showed comparable results to single-point error estimation. The error of the N1P1 amplitude depends on the number of averaging steps and amplification; in contrast, the error of the N1P1 amplitude is not dependent on the stimulus intensity.
  
  
  CONCLUSIONS
  Single-point error showed smaller N1P1 error and better coincidence with 1/√(N) function (N is the number of measured sweeps) compared to the known maximum-minimum criterion.
  
  
  CONCLUSIONS
  Evaluation of N1P1 amplitude should be accompanied by indication of its error. The retrospective approximation of this measurement error from the averaged data available in clinically used software is possible and best done utilizing the D-trace in forward masking artefact reduction mode (no stimulation applied and recording contains only the switch-on-artefact).
authors.affiliation: Department of Otorhinolaryngology, Christian-Albrechts-University of Kiel, Germany. Electronic address: hey@audio.uni-kiel.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Hey
authors.affiliation: Department of Otorhinolaryngology, Christian-Albrechts-University of Kiel, Germany. Electronic address: jmd@audio.uni-kiel.de.
authors.forename: Joachim
authors.initials: J
authors.lastname: Müller-Deile
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D001309:Auditory Threshold / Q000502:physiology*; D019929:Cochlear Implantation / Q000379:methods; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006311:Hearing Disorders / Q000503:physiopathology* / Q000628:therapy; D006801:Humans; D008297:Male; D015203:Reproducibility of Results
keywords: Cochlear implant; ECAP; Error; NRT