Chronic obstructive ETD (COETD) is defined as OETD that lasts for ≥3 months [4]. There was no effective treatment option for COETD before BDET. A prospective multicenter study suggested the improvement of COETD after BDET [6]. Patients with COETD intractable to pharmacological therapy demonstrated improved 7-item Eustachian Tube Dysfunction Questionnaire (ETDQ-7) scores and tympanometry findings following BDET [6]. Because ETD is an important etiology of COM, BDET can be a treatment option for COM with COETD. In 2019, the American Academy of Otolaryngology-Head and Surgery reported an insufficient consensus on the benefit of BDET in patients undergoing tympanoplasty or other middle ear surgery [2]. However, increasing evidence has been accumulated for BDET in patients undergoing middle ear surgery for chronic conditions.

Recently, Choi et al. [7] described successful treatment outcomes of BDET in patients with COETD that persisted following tympanomastoidectomy, among whom 62% (13/20) demonstrated improved Eustachian tube function following BDET, as estimated using the Valsalva maneuver [7]. Moreover, these patients showed improved hearing thresholds, while the unsuccessful Valsalva group had a worsened air-bone gap [7]. The rate of successful outcomes in this study was similar to those reported by previous studies of OETD [1]. A case-control study reported that patients who concurrently underwent BDET with tympanoplasty showed greater improvement in the air-bone gap than patients who underwent tympanoplasty without BDET (10.93±7.70 dB vs. 7.11±8.08 dB, P=0.033) [8]. Another prospective study reported favorable treatment outcomes of ETBD combined with cartilage tympanoplasty in patients with adhesive otitis media [9]. Therefore, ETBD can be an adjuvant surgical technique for patients who undergo middle ear surgery to treat chronic disorders.

The appropriate selection of patients for BDET may be a crucial factor for improving treatment outcomes. The outcome indicators for BDET include self-reported subjective measures of the ETDQ7 and a number of objective measures, such as tympanometry, audiometry, otoscopy, and the Valsalva maneuver [2]. Tubomanometry has been introduced to quantitatively evaluate Eustachian tube function, although the sensitivity was not satisfactory to detect ETD as surveyed using ETDQ-7 [10]. Temporal bone computed tomography (CT) combined with the Valsalva maneuver has been implemented to visualize the Eustachian tube [11]. However, the proportion of obstructed Eustachian tubes on CT during the Valsalva maneuver was not correlated with abnormalities in the Eustachian tube score [12]. Future research may be warranted to delineate the gold-standard measurement and establish correlations among the indicators of ETD, which will pave the way to establishing precise indications and achieving favorable treatment outcomes of BDET.