Keywords Cadaver - Dilatation - Endoscopy - Eustachian Tube/surgery - Feasibility Studies -
Middle Ear Ventilation - Preparation
Background
Dilatative Eustachian Tube Dysfunction (DETD) is a common condition affecting approximately
1–5% of the adult population, impairing middle ear ventilation, pressure equalization,
and drainage of middle ear secretions [1 ]
[2 ]
[3 ]
[4 ]. Chronic DETD is diagnosed when symptoms persist for more than 3 months and can
potentially lead to retraction of the eardrum, serous otitis media, chronic otitis
media, or the development of cholesteatoma [5 ]
[6 ]. DETD can be caused by a functionally relevant obstruction, a dynamic dysfunction
(e.g., muscular failure), or an anatomical obstruction [2 ]
[6 ]. It can also develop secondarily as a result of chronic inflammation, nasal or nasopharyngeal
obstruction, or muscular dysfunction. In addition to treating the underlying cause,
conservative therapy is the first-line treatment for improving tube function [7 ]
[8 ]
[9 ]
[10 ]
[11 ]. A so-called “Tube training” to improve Eustachian tube function usually involves
nasal irrigation, nasal steroids, and repeated autoinflation over several weeks. However,
there is currently no standardized conservative treatment protocol, and the use of
additional interventions such as short-term nasal decongestants or antihistamines
remains controversial [12 ]. If conservative measures are unsuccessful, balloon dilation of the Eustachian tube
(BDET) has established itself as the preferred escalation therapy for restoring tube
function [13 ]
[14 ]. This minimally invasive procedure, which is usually performed under general anesthesia,
aims to dilate the medial portion of the Eustachian tube, which consists of elastic
cartilage. Originally investigated in cadaver studies and later validated in clinical
trials, BDET is believed to compress pathological mucosal areas and promote their
healthy regeneration [15 ]
[16 ]
[17 ]. The procedure is considered safe, with the most common complications being mild
and self-limiting, such as epistaxis [14 ]. Other potential complications include mucosal injuries, hematotympanum, acute otitis
media, subcutaneous emphysema, rhinitis, damage to the ossicular chain or eardrum
resulting in conductive hearing loss, and temporary worsening of existing tinnitus.
The procedure involves inserting a catheter into the nasopharyngeal opening of the
Eustachian tube under endoscopic visual control [17 ]. Typically, BDET is performed as a two-handed technique, with the surgeon holding
a rigid endoscope in one hand and controlling the insertion instrument with the other.
After correct positioning in front of the torus tubarius, the balloon catheter is
inserted into the Eustachian tube up to a mark.
A pressure cylinder is used to fill the balloon with fluid so that the system reaches
a hydraulic pressure of 10 bar, which is maintained for a defined period of time.
In addition to the surgeon, the procedure requires a surgical assistant to operate
the pressure cylinder (insufflation of the balloon catheter) and assist the surgeon
with individual steps. Various BDET systems are available worldwide, differing in
terms of catheter diameter, length, and material composition. In the USA, most systems
are designed for single use, while in Germany, reusable systems with replaceable balloon
catheters are more commonly used ([Fig. 1 ]
a ) [18 ]
[19 ]. Increasingly concerns are being raised about the reliable sterilization of reusable
hollow instruments, particularly with regard to luminal structures that are difficult
to access [20 ].
Fig. 1
a Reusable combination introducers available in different angle variants. b Single-use BDET introducer (TubaInsert).
Traditionally, the balloon catheter is advanced into the Tuba Eustachii performed
with one hand while the other hand holds the endoscope. With the TubaInsert insertion
device ([Fig. 1 ]
b ), STM (Spiggle & Theis Medizintechnik, Overath, Germany) has launched a disposable
system on the European and US markets that requires the surgeon to use both hands
to insert the balloon catheter. This procedure requires the inserted endoscope to
be handed over to a surgical assistant.
This study examined the user-friendliness and technical safety of the TubaInsert-BDET
system with a 4-handed insertion technique on cadaver specimens. Both standardized
observations and subjective assessments by users were taken into account using a questionnaire,
whereby users with varying degrees of experience in this procedure were included.
Materials and methods
Participants
A study by Faulkner et al. showed that a sample size of 15 users detects at least
90% and, on average, 97.05% of usability problems in medical device testing [21 ]. Therefore, a sample size of 16 participants was chosen to ensure a high probability
of identifying potential usability concerns. ENT hospitals located as close as possible
to the study site were contacted in order to recruit ENT specialists or ENT physicians
in training aged 26–65 with no experience of the TubaVent Short and TubaInsert systems
for the study. When selecting participants, care was taken to ensure that the group
of subjects was as heterogeneous as possible, reflecting the target group of realistic
end users. In particular, variability in terms of professional experience in the ENT
field, previous experience with BDET, age, and gender were taken into account. All
interested persons who voluntarily agreed to participate after being contacted at
the study centers were included in the study. There was no selective selection or
rejection. Participants received a predetermined, outcome-independent lump sum for
their participation and were reimbursed for their travel expenses.
Study design
This usability study was conducted on fresh-frozen cadaver specimens to evaluate the
handling and user-friendliness of the 4-handed insertion technique of the TubaVent
Short Balloon Catheter with TubaInsert insertion device under standardized, risk-free,
and anatomically realistic conditions. It took place on June 3, 2023, at the European
Anatomy Campus in Mülheim an der Ruhr, Germany. Prior to data collection, all participants
were informed about the study, signed the consent form, and were briefed by the design
and development (D&D) department of STM (Spiggle & Theis Medizintechnik GmbH, Overath,
Germany) about the procedure, the device, and the study design. This usability study
followed ISO 13485 standards, which is relevant for the development of medical devices,
was conducted in accordance with the Instructions for Use (IFU) applicable in the
USA, and was taken into account in the FDA approval process. Each physician performed
a bilateral BDET on a head specimen, resulting in two balloon insertions per participant.
The surgeon and the surgical assistant stood facing each other, and the screen was
positioned at the head end. The surgical assistant was a trained surgical assistant
and employee of STM and was instructed to provide practical assistance to the participants
and explicitly not to answer any questions from the surgeons. In contrast to conventional
BDET systems, balloon catheter insertion requires 4-handed coordination. The insertion
instrument was inserted transnasally on the treatment side, while the endoscope was
advanced on the opposite side to the epipharynx. After identifying the pharyngeal
tubal ostium, the endoscope was handed over to the surgical assistant. The surgeon
stabilized the insertion device with one hand while advancing the balloon catheter
under direct visualization with the other hand ([Fig. 2 ]). After this step, the endoscope was handed back to the surgeon, allowing the assistant
to operate the the inflation pump with both hands.
Fig. 2 Four-handed insertion of the balloon catheter into the Eustachian tube.
The usability analysis was divided into two aspects: objective observation of product
use on a cadaver, followed by an interview. The BDET procedure was evaluated using
22 items. The steps can be divided into five categories: preparation, positioning
of instruments, four-handed catheter insertion, balloon insufflation, and completion
of the procedure. To evaluate the application, a neutral observer used a structured,
predefined documentation sheet to evaluate the progress of the procedure, the success
rate of the tasks, the number of attempts per step, and device-specific problems.
The observers in this usability study were medical engineers from STM's product development
department and were instructed to adopt a neutral, non-interventional observation
behavior in order to capture authentic user reactions. Task completion was evaluated
on a pass/fail basis, with “pass” defined as correct execution according to the US
instructions for use. The observer remained passive during the procedure.
Immediately after the procedure, participants completed structured questionnaires
to evaluate usability. This evaluation included age, professional experience, BDET
experience, dichotomous questions on all steps of the procedure, and an additional
field for comments.
Materials
Two simulated operating rooms with two identical workstations were used simultaneously,
each equipped with a different head specimen, video tower, light sources, and the
necessary ENT surgical instruments. Freshly frozen head specimens without otorhinolaryngological
abnormalities were obtained from MedCure Germany (Berlin, Germany). The TubaInsert
Type 45° insertion device ([Fig. 1 ]
b ) with the TubaVent Short balloon catheter from STM was used. The balloon catheter
is inserted through the working channel of the insertion device, and the balloon is
inflated to 10 bar for 2 minutes using an inflation pump. A 30-degree endoscope with
a diameter of 3 mm and a length of 14 cm was used.
Data analysis
The data were collected anonymously, compiled in Microsoft Excel (version 1808, Microsoft
Corp., Redmond, WA), and evaluated descriptively. Statistical analyses were performed
using SPSS software version 25.0 (SPSS Inc., Chicago, Illinois, USA). The Mann-Whitney
U test was used to determine whether inexperienced users needed multiple attempts
to complete the BDET steps. Task completion was evaluated using a pass/fail system,
with the device being considered usable if at least 95% of participants successfully
completed each task.
Results
Participant characteristics
The study involved 16 participants, including 4 women and 12 men; 22 ENT hospitals
had to be contacted for this purpose. The age range was 26–65 years, with a median
of 33 years (IQR 10). The median professional experience was 4.75 years (IQR 3.5,
range 0.5–31 years). On average, participants had 2 years of experience with BDET
(IQR 3.6, range 0–12 years). The cohort consisted of 11 assistant physicians, one
specialist, three senior physicians, and one chief physician, which corresponded to
the intended user group. None of the participants had previous experience with the
tested dilation system, and three (18.8%) participants had never used a BDET system
before.
Standardized observations
All participants successfully performed a bilateral BDET on the cadavers. Each participant
successfully completed all observed tasks, resulting in a success rate of 100% ([Table 1 ]). In particular, the steps associated with the 4-handed catheter insertion were
performed without any major problems by all participants.
Table 1 Observations.
Steps in the BDET procedure
Side
Successful (n)
Multiple attempts required (n)
*Steps related to two-handed insertion
BDET= Balloon dilation of the Eustachian tube ; L= left ; R= right
Preparation
16
0
16
0
16
0
16
0
16
0
16
0
16
0
16
0
16
0
16
0
Positioning
L
16
0
R
16
0
L
16
1
R
16
1
L
16
0
R
16
0
Four-handed catheter insertion
L
16
0
R
16
0
L
16
2
R
16
1
L
16
0
R
16
0
Balloon insufflation
L
16
0
R
16
0
L
16
0
R
16
0
End of procedure
L
16
0
R
16
0
L
16
0
R
16
0
L
16
0
R
16
0
16
0
The number of attempts per surgical step is listed in [Table 1 ]. All participants successfully completed 20 of the 22 steps on the first attempt
for both sides. However, some users needed several attempts for the remaining two
steps. Three participants (9.4% of the 32 dilated Eustachian tubes) required multiple
attempts to guide the catheter out of the insertion instrument on one side of the
cadaver. Their BDET experience did not differ significantly from those who completed
the step without difficulty (2 years versus 3 years, p= 0.9). In addition, 2 users
required multiple attempts to correctly rotate the olive of the TubaInsert toward
the tubal ostium. After removing the balloon catheter from the cadaver, a slight bend
was noted on one device. Observations confirmed that all tasks were performed according
to the BDET device instructions for use.
Usability survey
None of the users found that the safety or effectiveness of the product was compromised
by the transfer of the endoscope. In addition, all participants reported that they
had no problems taking over the endoscope from the assistant. Most users did not encounter
any significant problems during the other steps of the procedure. However, three users
(9.4% of the 32 dilated Eustachian tubes) reported difficulties advancing the balloon
catheter into the Eustachian tube. The complete results of the usability survey are
presented in [Table 2 ].
Table 2 Usability survey.
Question
Side
n
*Steps related to two-handed insertion
BDET= Balloon dilation of the Eustachian tube ; L= left ; R= right
Preparation
16
Positioning
L
16
R
16
L
16
R
15
L
16
R
16
Four-handed catheter insertion
L
16
R
16
L
0
R
0
L
16
R
16
L
14
R
16
Balloon insufflation
L
16
R
16
End of the procedure
L
16
R
16
L
16
R
16
L
16
L
16
R
16
Discussion
The subject of this study was to test the usability of a disposable BDET system that
requires a 4-handed insertion technique for the balloon catheter. This study examined
the user-friendliness of the system with a particular focus on the transfer of the
endoscope during application and the use of both hands to move the balloon catheter
forward. All participants successfully performed the necessary procedural steps for
bilateral BDET. In particular, the steps associated with bimanual catheter insertion
were easily mastered by all users. Furthermore, no participant considered the safety
or effectiveness of the system to be compromised.
Our results support previous BDET studies with various balloon dilatation systems,
which also demonstrated good feasibility [15 ]
[16 ]
[22 ]. Our standardized observations and survey data suggest that the TubaInsert system
is comparable to other established BDET systems in terms of user-friendliness. This
also applies to user groups with little or no experience with BDET systems. This study
is the first summative usability study of the TubaVent Short balloon catheter with
the TubaInsert insertion device from Spiggle & Theis and confirms its high user- friendliness
and safe handling.
The assessment of the BDET application was divided into 5 phases, comprising a total
of 22 steps. The steps in the categories of instrument preparation, balloon insufflation,
and completion of the procedure were successfully performed by all users on the first
attempt on both sides.
The step that some users encountered difficulties with occurred during instrument
positioning and was unrelated to the four- handed insertion. Two users needed several
attempts to rotate the insertion instrument to the tubal ostium. The second challenge
occurred during the 4-handed catheter insertion, where 3 users (9.4%) needed several
attempts to advance the balloon catheter on one side of the head specimen. This did
not result in a procedural error and was also unrelated to the user's level of experience.
However, since all difficulties occurred on the same side of the identical head, this
indicates anatomical rather than technical challenges. The results of the usability
survey were consistent with the observed results, as the same users reported difficulties
with the same procedural steps, confirming the validity of this study.
The four-handed technique has long been used in complex skull base surgery because
it increases the angle of exposure and creates more favorable space for instrumentation,
while also reducing complication rates [23 ]
[24 ]. In laparoscopic procedures, too, camera control is left to a surgical assistant,
allowing the surgeon to work with both hands. The endoscope can be guided with one
hand by experienced specialists; therefore, strictly speaking, a fourth hand is not
absolutely necessary. In our experience, both hands are generally used for better
stabilization, especially to optimize control and image stability in the confined
anatomical working space [Fig. 2 ]).
The potential advantage of this 4-handed technique in BDET is expected to be an improvement
in stability, maneuverability, and precision. It could also facilitate gentler insertion
of the balloon catheter through improved tactile feedback, which could reduce the
risk of mucosal injury. During the four-handed phase of the procedure, the surgical
assistant must maintain a stable view, which may seem unfamiliar to the surgeon at
first. However, the current results indicate that user-friendliness is not impaired
by the transfer of the endoscope. Even with the conventional, reusable combination
insertion instrument, a third hand from the surgical assistant is required to loosen
a screw, enabling the surgeon to insert the balloon catheter. However, due to the
proximity of the screw to both of the surgeon's hands, this step can be difficult
to coordinate. Compared to conventional combination insertion instruments, the tested
insertion instrument has a slimmer design without fingerrings. In addition, it is
designed as a single-use product, which could offer potential hygienic advantages,
as complete sterilization of reusable hollow instruments cannot be guaranteed in all
cases despite validated reprocessing procedures [20 ]. These aspects could be considered additional potential advantages of the TubaInsert
insertion device currently under investigation.
Similar to the traditional BDET technique, the surgeon and surgical assistant face
each other. However, this setup can lead to ergonomic challenges for the surgical
assistant, as the patient's head and the monitor are typically oriented toward the
surgeon. An ergonomic study evaluating different surgical setups found that the use
of two monitors and a central head position improved ergonomics for both the surgeon
and the assistant and potentially reduced the risk of complications [25 ].
One limitation of this study is that participation was voluntary, which means that
sampling bias cannot be ruled out with certainty. Nevertheless, the recruitment process
resulted in a heterogeneous group of subjects in terms of age, gender, and experience
in the ENT field. In addition, the use of cryopreserved head specimens, which may
undergo postmortem and thaw-related changes, could be considered a limitation of the
study. These changes could lead, among other things, to easier transnasal access,
a lower tendency to bleed, and reduced mucosal thickness. The advantages of performing
the study on cadaver specimens in the context of this usability study are standardized
conditions and a risk-free setting for the intended user group, including less experienced
users. This approach complies with regulatory requirements, such as those imposed
by the U.S. Food and Drug Administration (FDA) as part of product approval (Human
Factors Validation Testing). Comparative patient studies comparing 2-handed and 4-handed
BDET systems are needed to systematically investigate potential differences in application
(e.g., stability, maneuverability, precision, and tissue preservation) as well as
in terms of tube function and cost- effectiveness.
In summary, this study shows consistent correct use of a BDET system in which the
endoscope is handed over to the surgical assistant while the surgeon uses both hands
to insert the balloon catheter.
All participants successfully completed the procedure, and no major problems were
observed during the 4-handed insertion. This study on the disposable BDET system with
the TubaInsert insertion device and the TubaVent Short balloon catheter from STM demonstrates
safe handling and high user-friendliness, which was also positively evaluated by inexperienced
users. The present results suggest that the technique investigated could represent
a reliable alternative to conventional BDET systems with reusable insertion instruments.
