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