Round window stimulation with the Vibrant Soundbridge: Comparison of direct and indirect coupling.

<bold>Objectives/hypothesis: </bold>The purpose of this study was to measure the degree of coupling between the floating mass transducer (FMT) and the round window membrane (RWM) in patients with conductive and mixed hearing loss implanted with the Vibrant Soundbridge (VSB) device. The efficiency of direct and indirect coupling of the FMT to the RWM was compared by measuring differences between the initial prescription targets and the final settings of the VSB audio processor after fine-tuning.<bold>Study Design: </bold>Retrospective study.<bold>Methods: </bold>Investigation of a group of subjects with either conductive or mixed hearing loss implanted with the VSB, a device that uses a FMT coupled to the RWM. There were two subgroups: subjects in which coupling was direct (no interposed material) or indirect (interposed material). The functional gain, insertion gain, and compression characteristics of the device were measured to assess the efficiency of coupling and to investigate the proximity of the fitting to prescriptive targets.<bold>Results: </bold>Coupling for the subgroup with indirect coupling of the RWM was higher (better) than for the subgroup with direct coupling. The gain deviation from prescriptive targets was smaller for the subgroup with indirect coupling.<bold>Conclusions: </bold>The coupling method can have an effect on the coupling efficiency and the final electroacoustic settings of the device. The prescription targets were not accurate for the majority of subjects from either subgroup. Indirect coupling appears to provide more effective stimulation of the cochlea.<bold>Level Of Evidence: </bold>4. Laryngoscope, 127:2843-2849, 2017. [ABSTRACT FROM AUTHOR]