Balloon Dilation of the Eustachian Tube: Usability Analysis of a Four-Handed Insertion Technique

Abstract

Objective

Balloon dilation of the Eustachian tube (BDET) is the preferred escalation for dilatory dysfunction unresponsive to conservative therapy. The TubaInsert introducer and TubaVent Short balloon catheter form a slim single-use BDET system requiring a four-handed technique with intraoperative endoscope handover. This enables two-handed catheter insertion. This study evaluated usability.

Material and Methods

Sixteen ENT physicians (aged 26–65) without prior four-handed BDET experience performed bilateral procedures on cadaveric heads. A surgical assistant guided the endoscope. The procedure was divided into 22 steps assessed by observation and user surveys.

Results

All 16 participants completed bilateral BDET successfully. In 32 test runs, full balloon application was achieved. All procedural steps, including four-handed insertion, were performed correctly (100% success). Endoscope handover did not impair technical safety or feasibility.

Conclusions

This study shows high usability of the TubaInsert BDET system across users with varying experience. The four-handed technique appears reliable, technically safe, and potentially tissue-sparing.

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
Unpacking the inflation device and the extension hose		16	0
Unpack the TubaInsert		16	0
Unpacking the catheter		16	0
Unlock the inflation device by moving the lever to the left		16	0
Pull back the regulator of the inflation device to fill the syringe with NaCl/X-ray contrast medium		16	0
Lock the inflation device by moving the lever to the central position.		16	0
Attaching the extension hose		16	0
Build up pressure by turning the regulator to the right until the air is released.		16	0
Connect the catheter to the inflation device.		16	0
Loading the insertion instrument with the catheter		16	0
Positioning
Insertion of the system into the nose under endoscopic visualization	L	16	0
	R	16	0
Rotate the tip of the insertion instrument so that the angle is aligned with the trajectory of the Eustachian tube.	L	16	1
	R	16	1
Placing the system against the lateral epipharyngeal wall in front of the pharyngeal tubal ostium under endoscopic visualization	L	16	0
	R	16	0
Four-handed catheter insertion
Handover of the endoscope to the surgical assistant*	L	16	0
	R	16	0
Advancing the catheter out of the insertion instrument*	L	16	2
	R	16	1
Taking over the endoscope from the surgical assistant*	L	16	0
	R	16	0
Balloon insufflation
Inflate the balloon using the inflation device by turning the regulator to the right*	L	16	0
	R	16	0
Waiting time of 2 minutes at a constant pressure of 10 bar	L	16	0
	R	16	0
End of procedure
Turn the regulator counterclockwise with the lever in the center position	L	16	0
	R	16	0
Move the lever to the left	L	16	0
	R	16	0
Removing the system from the patient	L	16	0
	R	16	0
Retraction of the balloon in the insertion instrument		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
Was it possible to insert the catheter into the introducer device without any problems?		16
Positioning
Was it possible to locate the ostium of the Eustachian tube without any problems?	L	16
	R	16
Was it possible to insert the insertion instrument nasally to the ostium of the Eustachian tube without any problems?	L	16
	R	15
Was it possible to visually inspect and position the insertion device using an endoscope without any problems?	L	16
	R	16
Four-handed catheter insertion
Was it possible to hand over the endoscope to the surgical assistant without any problems?	L	16
	R	16
Was the safety and effectiveness of the product compromised by the transfer of the endoscope?*	L	0
	R	0
Was it possible to take over the endoscope from the surgical assistant without any problems?*	L	16
	R	16
Was it possible to advance the catheter into the Eustachian tube without any problems?*	L	14
	R	16
Balloon insufflation
Was it possible to inflate the catheter without any problems?*	L	16
	R	16
End of the procedure
Was it possible to remove the catheter without any problems?*	L	16
	R	16
Was it possible to withdraw the catheter from the Eustachian tube without any problems?*	L	16
	R	16
Was it possible to remove the insertion instrument together with the catheter without any problems?*	L	16
Was it possible to withdraw the catheter from the introducer sheath without any problems?	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.

Conflict of Interest

Teresa Schlummer and Murat Arslan-Steutermann are employees of the Design & Development (D&D) department at Spiggle & Theis Medizintechnik GmbH, Overath, Germany.

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Publication History

Received: 03 April 2025

Accepted after revision: 13 August 2025

Article published online:
09 October 2025