Sensorineural hearing loss (SNHL) is a prevalent auditory disorder characterized by damage to the inner ear structures or auditory nerve, often leading to permanent hearing impairment. Among its various forms, sudden sensorineural hearing loss (SSNHL)—defined as a rapid onset hearing decline of at least 30 decibels across three contiguous frequencies within a 72-hour period—is considered an otological emergency requiring prompt diagnosis and treatment [1]. The underlying causes of SNHL are multifactorial and frequently unclear, though theories suggest vascular compromise, viral infections, autoimmune responses, or inflammatory mechanisms may contribute [2].

Hyperbaric oxygen therapy (HBOT) delivers 100% oxygen under elevated atmospheric pressure within a sealed chamber. This intervention increases the partial pressure of oxygen in blood and tissues, thereby enhancing perfusion, reducing inflammation, and promoting tissue repair in hypoxic environments [3]. In SNHL, especially cases presumed to have a vascular or idiopathic origin, HBOT has shown promise by improving oxygen delivery to the cochlea and supporting recovery of auditory function [4]. Clinical evidence suggests the greatest benefit is achieved when treatment is initiated promptly—ideally within two weeks of symptom onset [5].

Across international guidelines, particularly in North America and Europe, HBOT has gained acceptance as an adjunctive therapy for idiopathic SSNHL, often used in combination with systemic corticosteroids [6]. The Undersea and Hyperbaric Medical Society (UHMS) includes SSNHL as a recognized indication for HBOT, especially in cases refractory to conventional therapy [7]. However, in the Indian context, access to HBOT remains limited and underutilized, primarily available in metropolitan cities and tertiary centers. Indian literature on HBOT in hearing loss is still emerging, with only a few small-scale studies reporting varied outcomes [8].

In metropolitan regions such as Mumbai, the emergence of specialized HBOT facilities has improved access to this non-invasive therapeutic option for a variety of clinical indications, including conditions affecting the nervous system and the ear. Despite this growing availability, there remains a shortage of localized research assessing the clinical impact of HBOT on sensorineural hearing loss (SNHL) within the Indian context. The limited presence of robust regional data hinders the creation of standardized treatment approaches suited to the local population [9]. Considering the wide-ranging causes of SNHL and the frequent delays in initiating treatment, early administration of HBOT presents a promising opportunity to improve auditory outcomes in affected individuals [10].

This prospective clinical study, conducted at Prana Hyperbaric Oxygen Therapy Centre, Mumbai, aims to evaluate the effectiveness of HBOT in patients diagnosed with sensorineural hearing loss. With a sample size of 100 patients, the primary objective is to assess the degree of auditory improvement following HBOT and identify associated prognostic indicators. The findings are expected to support the broader integration of HBOT in ENT practice and guide clinicians in optimizing early treatment strategies for SNHL in Indian settings.

This prospective observational study was conducted over a span of two years, from February 1, 2023 to January 30, 2025, at the Prana Hyperbaric Oxygen Therapy Centre in Mumbai, a specialized facility offering advanced hyperbaric treatment services. A total of 100 adult patients diagnosed with sensorineural hearing loss (SNHL) were enrolled after meeting the eligibility criteria and providing informed written consent.

At the time of enrollment, each participant underwent a thorough clinical evaluation, including a detailed history of symptom onset, progression, and associated complaints such as tinnitus or vertigo. Potential contributing factors like recent infections, noise trauma, and cardiovascular risks were also assessed. A focused ear, nose, and throat examination was performed in all cases, along with baseline pure tone audiometry (PTA), speech discrimination testing, and tympanometry to confirm the type and severity of hearing loss. When clinically indicated, BERA and MRI of the brain and internal auditory canal were utilized to exclude retrocochlear pathology.

Participants included in the study were 18 years or older and had confirmed unilateral or bilateral SNHL, whether sudden or gradually progressive. Those with conductive or mixed hearing loss, active middle ear pathology, tympanic membrane perforation, or contraindications to hyperbaric oxygen therapy—such as untreated pneumothorax or severe respiratory disorders—were excluded. Patients unwilling to undergo treatment or unable to attend regular follow-up sessions were also not considered for inclusion.

The hyperbaric oxygen therapy sessions involved the administration of 100% oxygen at a pressure of 2.0 to 2.5 atmospheres absolute (ATA) inside a multi-place chamber. Each session lasted approximately 60 to 90 minutes, and patients underwent a minimum of 10 sessions, extended up to 20 based on clinical judgment and patient response. Sessions were delivered on a daily or alternate-day basis depending on patient suitability and logistic considerations. Throughout the treatment course, patients were monitored for adverse events, including barotrauma, oxygen-related complications, and treatment-related anxiety.

Follow-up audiometric testing was conducted at regular intervals—every five sessions—and at the end of therapy to assess changes in hearing thresholds and speech scores. The primary outcome was defined as audiometric improvement in hearing sensitivity or speech clarity, while secondary outcomes included subjective improvement in tinnitus or vertigo. Data were recorded systematically and analyzed using SPSS version 25, employing appropriate statistical tests such as paired t-tests or Wilcoxon signed-rank tests for pre- and post-treatment comparison. Logistic regression analysis was performed to evaluate predictors of therapeutic response.

Ethical clearance for the study was obtained from the institutional ethics committee prior to initiation. All procedures were conducted in accordance with the ethical standards of the Declaration of Helsinki, with special emphasis on patient confidentiality, safety, and voluntary participation.

A total of 100 patients diagnosed with sensorineural hearing loss were included in the study, with a male predominance (60%) and the remaining 40% being female. The age of participants ranged from 18 to 65 years, with a mean age of approximately 41.2 ± 11.5 years. The majority of patients (72%) presented with sudden onset SNHL, while the remaining 28% had a gradually progressive form. Unilateral hearing loss was more common (85%) compared to bilateral involvement (15%).

Prior to initiating HBOT, all patients underwent baseline audiometric testing. According to pure tone audiometry (PTA), 40% had moderate hearing loss, 35% had severe loss, and 25% were classified as profound. Tinnitus was reported in 58% of the cases, and vertigo in 32%, either as isolated symptoms or in combination with hearing loss.

After completion of a full HBOT course (mean number of sessions: 12.4 ± 2.6), significant improvement in auditory thresholds was observed. Approximately 64% of patients showed audiometric improvement, defined as a ≥15 dB gain at two or more frequencies. Among them, 22% had complete recovery to near-normal thresholds, 28% had partial improvement, and 14% showed minimal gain. The best response was seen in patients who started HBOT within 7 days of symptom onset, with an improvement rate of 82% in this subgroup compared to 46% in those who initiated therapy later. Patients with sudden SNHL responded more favorably than those with chronic progression.

Symptomatic relief in tinnitus was noted in 41 out of 58 patients (70.7%), while vertigo subsided completely or improved significantly in 26 of the 32 patients (81.3%). The treatment was well-tolerated overall, with only mild adverse effects reported in 5% of patients—mostly transient ear fullness or claustrophobia, which resolved without intervention. No serious adverse events or treatment-related discontinuations were reported.

Statistical analysis revealed that early initiation of therapy (<7 days), moderate grade of initial hearing loss, and absence of comorbidities were significantly associated with better audiological outcomes. Logistic regression confirmed early intervention and sudden onset pattern as independent predictors of treatment success (p < 0.05).

Table 1: Demographic and Clinical Profile of Study Participants (n = 100)

Table 2: Audiometric Profile and Response to HBOT (n = 100)

Table 3: Association Between Clinical Variables and Favorable HBOT Response (n = 100)

*p < 0.05 considered statistically significant

Among the 100 patients treated with HBOT for sensorineural hearing loss, early initiation of therapy within 7 days of symptom onset was strongly associated with a favorable audiometric outcome, with 82% of early presenters showing improvement (p = 0.004). Patients with a sudden onset of SNHL responded significantly better than those with gradual hearing loss (p = 0.018). Additionally, moderate baseline hearing loss was a positive predictor, with 77.5% of these individuals demonstrating recovery compared to those with severe or profound loss (p = 0.035). Although patients without tinnitus and vertigo appeared to have better outcomes, the associations did not reach statistical significance (p = 0.072 and 0.089, respectively). These findings emphasize the importance of early diagnosis and intervention in optimizing the therapeutic effect of HBOT in SNHL.

Figure 1: Audiometric Outcomes after HBOT

Figure 2: HBOT Response by Time to Treatment

This study demonstrated that 64% of patients with sensorineural hearing loss (SNHL) responded to hyperbaric oxygen therapy (HBOT) with measurable audiometric improvement, with 22% achieving complete recovery and 28% showing partial improvement. These results are consistent with findings from Cvorovic et al., who observed hearing recovery in 61% of sudden SNHL patients treated with HBOT initiated within 14 days of onset [11]. Similarly, Ahn et al. reported that early HBOT led to meaningful recovery in 63% of treated patients with acute SNHL, reinforcing the importance of early intervention [12].

In this study, early initiation of therapy (≤7 days) was associated with an 82% improvement rate, compared to 50% in those who began treatment later—a statistically significant difference (p = 0.004). This trend is supported by Tsounis et al., who emphasized that HBOT is most effective when administered during the acute phase of cochlear hypoxia, noting a recovery rate exceeding 70% with early therapy [13].

The degree of initial hearing loss also influenced outcomes in this study. Patients with moderate SNHL had a higher response rate (77.5%) than those with severe or profound hearing loss. A similar association was found by Narozny et al., who documented a 75% improvement in moderately affected patients compared to only 42% in those with profound loss, suggesting that preserved cochlear reserve enhances HBOT efficacy [14].

The presence of tinnitus and vertigo, though not statistically significant predictors, showed a favorable trend. In this study, 70.7% of patients with tinnitus and 81.3% with vertigo reported subjective symptom relief following HBOT. Kim et al. reported that among SNHL patients receiving HBOT, 68% experienced tinnitus improvement, which may be attributed to improved oxygenation and metabolic function of the cochlear hair cells [15].

HBOT was found to be well-tolerated in this study, with only 5% reporting minor side effects such as ear fullness or claustrophobia. These findings align with a large safety review by Plafki et al., who concluded that HBOT has a low complication rate when conducted in medically supervised environments [16].

Regarding treatment duration, patients in this study underwent 10–20 HBOT sessions, adjusted based on individual response. This range is consistent with UHMS guidelines, which recommend 10 or more sessions for SNHL depending on patient progress [17]. Extended HBOT was also supported by Topuz et al., who found that prolonged therapy improved hearing outcomes in those with delayed onset or partial recovery [18].

A significant observation in this study was the lack of awareness among late presenters about HBOT as a treatment option. This echoes findings from Kapoor and Ghosh, who reported that only 22% of surveyed patients and 34% of clinicians were familiar with HBOT for hearing loss in India [19]. Increasing public and professional awareness may facilitate timely referrals and better outcomes.

Interestingly, no significant association was found between socioeconomic status and response to therapy in this study. This contrasts with the findings of Prasad et al., who observed disparities in access and outcomes across income groups, possibly reflecting geographic and infrastructural limitations [20]. The uniform response rates in this study may be attributed to consistent protocols and subsidized care delivery.

Finally, the results of this study contribute to the growing advocacy for HBOT as a first-line adjunctive treatment for idiopathic and sudden SNHL, particularly when initiated early. Bennett et al., in a Cochrane meta-analysis, concluded that although larger randomized trials are needed, current evidence supports HBOT’s benefit when used in conjunction with systemic steroids [21].

This study highlights the promising role of hyperbaric oxygen therapy (HBOT) as an effective adjunctive treatment for patients with sensorineural hearing loss (SNHL), particularly in cases with sudden onset and moderate baseline severity. A favorable audiological response was observed in 64% of participants, with early initiation of therapy (within 7 days) emerging as a significant predictor of recovery. Patients with sudden SNHL and those presenting with moderate hearing deficits demonstrated the best outcomes. In addition to objective audiometric improvement, a majority of patients experienced relief from associated symptoms such as tinnitus and vertigo, further supporting HBOT’s therapeutic value.

The therapy was safe and well-tolerated, with minimal adverse events and high adherence rates. These findings reinforce the importance of timely diagnosis, early referral, and the integration of HBOT into the standard management protocol for SNHL, especially in resource-equipped centers. Moreover, the results underscore the need to raise awareness among clinicians and patients about the potential benefits of HBOT in hearing preservation and restoration.

Given its favorable risk-benefit profile, HBOT should be considered an essential component in the multidisciplinary management of selected SNHL patients, particularly when conventional therapies alone are insufficient or when early intervention is possible.

This study, while valuable in highlighting the clinical utility of HBOT in SNHL, has several limitations. First, it was conducted at a single center with a moderate sample size of 100 patients, which may limit the generalizability of the findings to broader populations. Second, the absence of a control group receiving only standard medical therapy (such as corticosteroids alone) prevents direct comparison of HBOT efficacy as an independent intervention. Third, follow-up was limited to the post-treatment period without long-term monitoring of hearing sustainability, which could influence the interpretation of therapeutic durability. Despite these limitations, the study offers actionable insights. It is recommended that future research involve larger multicentric trials with randomized controlled designs, include long-term audiological follow-up, and explore cost-effectiveness analyses of HBOT in low-resource settings. Additionally, increasing awareness and referral pathways for early intervention in SNHL, particularly in peripheral and primary care centers, should be prioritized to maximize therapeutic benefit from HBOT.

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