Physician Referral Guide: Hyperbaric Oxygen for Sudden Sensorineural Hearing Loss

Assessing the patient before referral

While arranging hyperbaric and otolaryngology assessment, the referring clinician should:

• Confirm the sensorineural pattern and exclude a conductive cause at the bedside (for example, with tuning-fork tests and otoscopy to rule out cerumen impaction or middle-ear effusion). Formal pure-tone audiometry establishes the baseline against which treatment response is judged.
• Begin first-line corticosteroid therapy without waiting for the hyperbaric consultation, using high-dose oral or intratympanic corticosteroids per local ENT protocol. HBOT is adjunctive to this therapy, not a substitute for it.
• Document the exact time of onset and the trajectory since, because the time from onset directly determines expected benefit.
• Record the severity at presentation (the pure-tone average and affected frequencies) and any associated symptoms such as tinnitus, vertigo, or aural fullness.
• Screen for HBOT cautions that may need concurrent management, particularly recent middle-ear or sinus surgery, severe ear barotrauma, or significant bullous lung disease.
• Exclude identifiable causes that would change management (for example, retrocochlear pathology, recent ototoxic exposure, or acoustic trauma); the diagnosis is idiopathic by definition.

What the evidence supports

The reference evidence is the Cochrane review (Bennett et al. 2012, 7 RCTs, 392 participants), which found that HBOT combined with standard therapy improved the absolute pure-tone average by 15.6 decibels and was associated with a higher rate of hearing improvement compared with standard therapy alone. The Cochrane authors noted that, while hearing improved significantly, the clinical significance of the change remained uncertain, and the benefit was concentrated in patients treated within 14 days of onset. On this evidence base, the Undersea and Hyperbaric Medical Society approved ISSNHL as the 14th recognised hyperbaric indication in 2011, carried into its indications manual in 2014 and forward through the current edition, with a strong level-of-evidence rating.

Trial-level data are broadly consistent with this pooled result. Across Lamm et al. and subsequent trials, HBOT plus corticosteroids tended to outperform corticosteroids alone in improving pure-tone thresholds and word-recognition scores, with the larger effects in patients who had severe (61 to 80 dB) or profound (greater than 80 dB) hearing loss at presentation. Two prognostic variables emerge consistently across studies: time from onset to treatment (the strongest single predictor) and severity at presentation (the second strongest).

The mechanistic rationale is well established. The cochlea has a high metabolic demand and a tenuous end-arterial blood supply, and ISSNHL is associated with cochlear hypoxia. Hyperbaric oxygen raises the plasma oxygen content 10- to 15-fold, allowing oxygen to dissolve directly into the perilymph and endolymph and reach the hair cells even where the vascular supply is compromised. Hyperbaric oxygen is also thought to attenuate the inflammatory cascade, reduce neutrophil adhesion to cochlear microvascular endothelium, and limit lipid peroxidation in hair cells.

The evidence is not without limits. The constituent trials are small and clinically heterogeneous, and the most reliable positive signal is for early, adjunctive treatment in patients with more severe loss. There is no robust evidence that HBOT reverses long-established hearing loss, which is why the treatment window is central to the referral decision. Further detail on the indication is available on the sudden sensorineural hearing loss condition page.

The Canadian referral pathway

ISSNHL is treated as a time-sensitive elective indication at Canadian hospital-based hyperbaric programmes and is covered by provincial health insurance with physician referral. Because of the short treatment window, most programmes prioritise ISSNHL referrals for prompt consultation, with treatment beginning as soon as the consultation confirms suitability. Patients should also have urgent otolaryngology evaluation in parallel.

• Ontario: refer to the Toronto General Hospital (UHN), Hamilton General Hospital, or The Ottawa Hospital programmes; covered under OHIP.
• British Columbia: route to Vancouver General Hospital (Leon Judah Blackmore Pavilion), the hospital chamber for the province; covered under MSP.
• Alberta: route to Misericordia Community Hospital (Edmonton) or Foothills Medical Centre / Arthur J.E. Child Comprehensive Cancer Centre (Calgary); covered by Alberta Health.
• Quebec: RAMQ covers Hôpital du Sacré-Cœur de Montréal and Hôtel-Dieu de Lévis.
• Provinces and territories without an in-province hospital programme (Manitoba, New Brunswick, PEI, Yukon, NWT, Nunavut): inter-provincial referral to the nearest chamber, most commonly Misericordia Edmonton or the Ontario programmes. Given the time-sensitivity, arrange this referral without delay.

How to use the research list below

The list contains every sudden sensorineural hearing loss study in the Canada Hyperbarics database that was published in 2020 or later and has a freely available full-text version, each linked directly to that full text. Paywalled and abstract-only studies are excluded, and retracted studies are removed. This is a reference list, not a set of summaries. Counts and the open-access set refresh each quarter.