3.2 Participants
For participation, the inclusion criteria were German native speakers aged between 18 to 80 years with middle ear disease resulting in a CHL or MHL, unilateral or asymmetric hearing loss (HL). The results were compared with those of healthy subjects with a normal hearing ability. Patients with ear surgery of the contralateral ear, retrocochlear or central auditory disorders, skin diseases or other surgical conditions that may prevent the attachment of the adhesive adapter of the ADHEAR system were excluded.
Overall, 23 patients of the Department of Otorhinolaryngology, Head and Neck Surgery with middle ear disease (group 1) and 10 healthy volunteers as a control group participated in this prospective single-subject repeated-measure study (Table 1).
All subjects were informed about the aims of the study and provided their written consent.
3.3 Procedure
All patients and healthy subjects obtained a detailed medical report and an ear, nose and throat examination. The patients with middle ear disease were identified by otoscopy. In all healthy subjects, a chronic otitis media was excluded.
All participants obtained a pure tone audiometry and free-field speech audiometry under various conditions, i.e., in the unaided situation and aided situations using the ADHEAR system and the softband BAHA 5 Power system. Furthermore, to assess the hearing ability before and after using the ADHEAR system, all patients were asked to fill out the questionnaire.
3.4 Outcome measures
All audiological assessments were conducted in an audiometric sound attenuated room, using calibrated signals and equipment according to accepted ISO standard. For assignment of the participants a pure tone audiometry was performed measuring the air and bone conduction thresholds at 0.5, 1, 2, 3, 4, 6, and 8 kHz. The PTA4 was calculated for the bone conductive and air tone thresholds across the frequencies of 0.5, 1, 2, and 4 kHz.
The speech intelligibility tests were conducted in the free field using the Freiburger monosyllables word test in quiet and in noise. The loudspeakers were positioned 1 m away from the participants’ head. In quiet, i.e., under the S0 condition, the speech intelligibility was measured at 65 dB SPL. In noise, i.e., under the S0N0 condition, the speech intelligibility was measured with a fixed noise level at 60 dB SPL and a speech level at 65 dB SPL, resulting in a signal-to-noise ratio (SNR) of 5 dB. All speech intelligibility measurements were performed in the unaided situation and the aided situation with the ADHEAR system. In order to compare the performance of the ADHEAR system, 10 patients and the 10 healthy subjects were also fitted with a softband BAHA system using the BAHA 5 Power system.
In order to measure the speech intelligibility of the ipsilateral ear as isolated as possible, the contralateral ear was masked using an earplug (Oropax®) if applicable.
In the control group, the healthy subjects with normal or age-appropriate hearing ability, both ears were plugged with an earplug (Oropax®) reaching 40 ± 8.2 dB CHL (ranging 22.5-50 dB).
A questionnaire focused on several aspects encountered in applying the ADHEAR system, namely handling of the system, hearing sensation and problems.
3.5 Data analyses
Statistical tests (Kolmogorov Smirnov test and Shapiro-Wilks test) indicated non-normal distribution for all parameters. Nonparametric tests were performed for group comparisons whenever appropriate. Pearson statistics were used for correlational analyses. The alpha level was set to 0.05. SPSS 27.0 (SPSS Inc. Chicago, IL, USA) was used for statistical analyses. In this paper, we will only discuss significant results.
4 Results