Objective: In February of 2020, a cochlear implant manufacturer initiated a field action notice to remove an electrode array from circulation. In this study, we quantify device failure and specifically examine the relationship of impedance change as a precursor to declining speech perception.
Study Design: Retrospective/Cohort Study.
Setting: Tertiary Referral Center
Patients: 48 patients (51 devices) were implanted between October 2017 to December 2019. Post-operative speech perception (AzBio) scores at 12 months were used as a reference, with further testing at 3-6 month intervals. Degree of change in impedances from 1-month post-activation were analysed at similar intervals.
Exclusion Criteria included: <18 years of age, medical/surgical/soft failures and English as an additional language.
Interventions: Diagnostic.
Main Outcome Measures: Device failures were confirmed by the following: impedance levels < 3.0μΩ and/or declines of 50% from their original (baseline) value, and speech perception decline >15% on the AzBio test.
Results: To date, 11 (22%) electrodes have failed. The number of devices currently being monitored for suspected failure is 12 (24%). There are statistically significant differences (p < 0.001), in speech perception scores and impedance levels between normative and suspect/failed devices. The entire electrode array (Channels 1-16) may be impacted. There was no relationship between degree of impedance change and speech scores. The average length of time for a change to become apparent was 22 months (+/- 5) post implantation.
Conclusions:Impedance values can be used as a reliable indicator of future decline facilitating patient counselling and possible early intervention. No relationship was identified that corelated changes in impedance with speech perception.
Define Professional Practice Gap & Educational Need: Cochlear implant recalls are rare unfortunate events. It is imperative that a patient have access to recalled device performance and be provided the requisite information for best possible counselling. Impedance values can be used to inform patient decision making.
Learning Objective: The use of impedance values to monitor implant function and possible decline. Changes in impedance of >50% or a drop of 3.0 uO provide a strong suggestion of future change in device function.
Desired Result: If impedance decline can be used as a predictor for a decline in speech performance.