Hyperbaric oxygen therapy can improve hearing recovery in idiopathic sudden sensorineural hearing loss (ISSNHL) when started within 14 days of onset, particularly for severe and profound hearing losses. ISSNHL is the most recently recognised hyperbaric indication, added to the UHMS list as condition number 14, and is covered by every Canadian provincial health-insurance plan at hospital-based hyperbaric programmes. Early referral, ideally within the first week, is the single most important factor in the likelihood of meaningful recovery.
Quick Answer
Does HBOT help sudden sensorineural hearing loss (idiopathic)? Hyperbaric oxygen therapy can improve hearing recovery in idiopathic sudden sensorineural hearing loss (ISSNHL) when started within 14 days of onset, particularly for severe and profound hearing losses. ISSNHL is the most recently recognised hyperbaric indication, added to the UHMS list as condition number 14, and is covered by every Canadian provincial health-insurance plan at hospital-based hyperbaric programmes. Early referral, ideally within the first week, is the single most important factor in the likelihood of meaningful recovery.
Idiopathic sudden sensorineural hearing loss (ISSNHL) is defined as a rapid loss of hearing of 30 decibels or more across three or more contiguous audiometric frequencies, occurring over 72 hours or less, with no identifiable cause on initial evaluation. The hearing loss is sensorineural, meaning it originates in the cochlea or auditory nerve rather than the conductive (middle ear) apparatus. Most cases are unilateral. Patients often describe waking up with a sensation of fullness or muffled hearing in one ear, or noticing the loss when answering the phone or putting in earbuds.
The condition affects approximately 5 to 20 people per 100,000 per year in published Canadian and international epidemiology, with a peak incidence in the fifth and sixth decades and no clear sex predominance. Up to one-third of cases recover spontaneously, but the remaining two-thirds are left with permanent hearing loss in the affected ear unless treated. Approximately 30 percent of cases are associated with persistent or new tinnitus, and 30 to 40 percent have associated vertigo at presentation, typically resolving within days even when the hearing loss persists.
The pathophysiology of ISSNHL is incompletely understood, which is why the condition is labelled idiopathic. Three mechanisms are thought to account for the bulk of cases: viral inflammation of the cochlea or auditory nerve (often inferred from preceding upper-respiratory illness), microvascular ischemia or thrombosis affecting the labyrinthine artery, and autoimmune inner-ear disease. The unifying clinical feature is acute hypoxia of the highly metabolically active cochlear hair cells and stria vascularis. Treatment must be delivered before the hair cells undergo permanent apoptotic loss, which is why time from symptom onset to treatment is the single most important prognostic factor.
Hyperbaric oxygen therapy treats ISSNHL by overcoming the cochlear hypoxia that underlies most presentations of the disease. The cochlea has the highest oxygen consumption per gram of any tissue in the body and is supplied by a single small end-artery (the labyrinthine artery) with no collateral circulation. Even modest reductions in oxygen delivery to the cochlea can produce hair-cell ischemia within minutes. Inside a hyperbaric chamber at 2.0 to 2.5 ATA on 100 percent oxygen, plasma oxygen content rises 10- to 15-fold, and oxygen dissolves directly into the perilymph and endolymph that bathe the cochlear hair cells. This bypasses the compromised vascular supply entirely, restoring tissue oxygen tension and allowing the hair cells and stria vascularis to resume aerobic metabolism.
Beyond raw oxygen delivery, hyperbaric oxygen attenuates the inflammatory cascade that contributes to ongoing cochlear injury after the initial hypoxic insult. It blocks neutrophil adhesion to cochlear microvascular endothelium, reduces lipid peroxidation in the hair cells, supports endogenous antioxidant systems, and may modulate the immune response in suspected autoimmune-mediated cases. The combination of restored oxygenation and reduced inflammatory injury creates a window in which cochlear function can recover before the hair cells undergo permanent apoptotic loss.
The time-sensitivity of HBOT in ISSNHL is grounded in this mechanism. Hair cells that have already entered the apoptotic pathway cannot be rescued, and the apoptotic decision is made within days of the hypoxic insult. This is why every published study showing benefit from HBOT in ISSNHL also shows that the benefit is concentrated in patients treated within 14 days of symptom onset, with the strongest signal in patients treated within the first week. Patients presenting after 14 days are typically still offered HBOT in Canadian programmes if hearing loss is severe or profound, but with appropriately tempered expectations.
Typical Treatment Protocol
Standard course is 2.0 to 2.5 ATA for 90 minutes per session, delivered five days per week for 10 to 20 total sessions (typically two to four weeks). HBOT is most often combined with high-dose oral or intratympanic corticosteroids (the standard non-hyperbaric treatment) rather than used as monotherapy. Many Canadian programmes follow a stepped protocol: an initial trial of high-dose oral steroids while booking the HBOT consultation, addition of HBOT within the first 14 days of onset (ideally within 7 days), and consideration of intratympanic salvage steroids in parallel. Audiometry is performed at baseline, mid-course (around session 10), and end of treatment, with the change in pure-tone average (PTA) and word-recognition scores serving as the primary outcome metrics. The course can be extended to 30 sessions in cases that show partial response and continued improvement at the standard end-point.
Level B - Moderate Evidence
Supported by controlled studies and clinical evidence
A Cochrane Review (Bennett 2012, updated 2020, 7 RCTs and 392 participants) concluded that HBOT combined with standard medical therapy improved the absolute pure-tone average (PTA) by 15.6 decibels and produced a substantially higher rate of clinically significant hearing improvement compared to standard therapy alone. The benefit was concentrated in patients treated within 14 days of onset.
The Lamm et al. trial and several subsequent randomised studies showed that HBOT plus corticosteroids outperformed corticosteroids alone in improving pure-tone thresholds and word-recognition scores, with the largest effect sizes in patients with severe (61 to 80 dB) or profound (>80 dB) hearing loss at presentation.
Time from onset to treatment is the strongest single prognostic variable in published cohorts. Treatment within 7 days produces the best outcomes; treatment within 14 days remains worthwhile; treatment after 14 days produces progressively diminishing benefit, although Canadian programmes often still offer HBOT for severe and profound hearing losses presenting late.
Severity at presentation is the second strongest prognostic variable. Severe and profound hearing losses (greater than 60 to 80 dB PTA) respond more dramatically to HBOT than mild-to-moderate losses, in part because the ceiling for improvement is higher and in part because severe losses appear to have a higher proportion of recoverable ischemic injury.
Tinnitus and vertigo often improve in parallel with hearing recovery during HBOT, even in patients whose audiometric thresholds improve only modestly. Quality-of-life metrics tracked alongside audiometry show consistent improvement across the published trials.
ISSNHL was added as the 14th UHMS-recognised hyperbaric indication in 2011 (Indications, 13th edition), reflecting the accumulated randomised evidence base. It remains the most recently added recognised condition. The American Academy of Otolaryngology updated its clinical practice guideline in 2019 to formally include HBOT as an option (offer) within the first 14 days of onset.
Highest-evidence-tier studies tagged to this condition in the Canada Hyperbarics research database, ranked by evidence tier (1 = meta-analysis or RCT, 2 = cohort, 3 = case series), most recent first.
Laryngoscope · 2026 · Meta-Analysis
Diving Hyperb Med · 2025 · Meta-Analysis
JAMA Otolaryngol · 2022 · Meta-Analysis
Audiol Neurootol · 2022 · Prospective Study
Studies in our database that include a ClinicalTrials.gov registration. Trial registration is a marker of methodological rigour because the protocol, primary outcome, and analysis plan are deposited before enrolment begins.
Experimental and therapeutic medicine · 2022 · RCT · PMID 35222719
Most patients are referred to a hospital hyperbaric programme by their family physician or otolaryngologist (ENT specialist) once an audiogram has confirmed the sudden sensorineural pattern and standard high-dose corticosteroid therapy has been initiated. Time from initial presentation to hyperbaric chamber should be days, not weeks; the receiving hyperbaric medicine team will typically prioritise ISSNHL referrals for next-available consultation, often within 48 to 72 hours.
At the hyperbaric consultation, the team confirms the diagnosis, reviews the timeline (date of onset, current corticosteroid plan, any associated tinnitus or vertigo), takes a baseline audiogram if not already available, and screens for absolute and relative contraindications. The treatment course typically begins within one to three days of the consultation, often the same day if logistics allow. Daily sessions begin immediately. You change into cotton scrubs, enter the chamber, and lie down (in a monoplace) or sit in a recliner (in a multiplace with multiple patients). Pressurisation takes five to ten minutes and feels like the descent in an aircraft, with ear-clearing as in flying. During the 90-minute treatment phase you breathe pure oxygen by mask or hood. Decompression takes another five to ten minutes.
Audiograms are repeated at the midpoint and at the end of the course to track recovery. Most responders show measurable improvement in pure-tone thresholds by sessions 8 to 12. Tinnitus and vertigo often resolve in parallel even in cases where hearing loss persists. Side effects, when they occur, are usually limited to ear barotrauma during pressurisation (manageable with pressure-equalisation techniques and rarely a tympanostomy tube), temporary near-sightedness, and mild fatigue. The hyperbaric team coordinates closely with your referring ENT throughout the course and at the post-treatment audiogram review.
Idiopathic sudden sensorineural hearing loss is the most recently added Health Canada-recognised hyperbaric indication and is covered by every provincial health-insurance plan at hospital-based hyperbaric programmes. The clinical reality is that early referral matters more for ISSNHL than for almost any other recognised hyperbaric condition; provincial wait times that work for chronic indications can foreclose the treatment window for ISSNHL. Most Canadian hospital programmes give ISSNHL referrals priority routing as a result.
In Ontario, OHIP covers treatment at the three hospital programmes (Toronto General / UHN, Hamilton General Hospital, The Ottawa Hospital). Most Ontario otolaryngologists know the referral pathway; if the referring physician is unsure, the Hamilton General Hospital and Toronto General Hospital hyperbaric medicine teams accept direct ENT-to-HBOT consultation requests. Select eligible Independent Health Facilities may also bill OHIP for approved indications, with eligibility varying by facility.
Alberta Health (AHCIP) covers treatment at Misericordia Community Hospital in Edmonton (Covenant Health) and the Foothills Medical Centre / Arthur J.E. Child Comprehensive Cancer Centre in Calgary (Alberta Health Services). British Columbia (MSP) covers treatment at Vancouver General Hospital's Leon Judah Blackmore Pavilion. Quebec (RAMQ) covers treatment at Hôpital du Sacré-Cœur de Montréal and Hôtel-Dieu de Lévis. Nova Scotia (MSI), Newfoundland and Labrador (MCP), and Saskatchewan also cover hospital-delivered treatment.
For patients in provinces or territories without an in-province hospital hyperbaric programme (Manitoba, New Brunswick, Prince Edward Island, Yukon, Northwest Territories, Nunavut), inter-provincial referral must be expedited because of the 14-day treatment window. The most common destinations are Misericordia Edmonton (for prairie and territorial patients) and the Ontario hospital programmes. Air ambulance transport is occasionally arranged for severe and time-critical cases when no in-province option exists. Some private hyperbaric clinics also offer ISSNHL treatment on a self-pay basis, typically at $175 to $350 per session; private extended health plans may cover specific indications when accompanied by a physician referral.
Hyperbaric oxygen therapy for the 14 Health Canada-recognised conditions, including Sudden Sensorineural Hearing Loss (Idiopathic), is delivered at the 11 hospital hyperbaric programmes located in seven provinces (Ontario, Quebec, British Columbia, Alberta, Nova Scotia, Newfoundland and Labrador, and Saskatchewan). The six provinces and territories without an in-province hospital programme (Manitoba, New Brunswick, Prince Edward Island, Yukon, Northwest Territories, and Nunavut) route patients to the nearest receiving hospital programme. Use the links below for province-specific coverage, referral pathway, and emergency routing details.
Hospital + Private
OHIP (Ontario Health Insurance Plan)
Hospital Only
MSP (Medical Services Plan)
Hospital + Private
Alberta Health / AHCIP
Hospital Only
RAMQ
Disrupted
Saskatchewan Health Authority
No Hospital Chamber
Manitoba Health
Hospital Only
MSI (Medical Services Insurance)
No Hospital Chamber
Medicare NB
Hospital Only
MCP (Medical Care Plan)
Out-of-Province Referral
Health PEI
Out-of-Province Referral
Yukon Health and Social Services
Out-of-Province Referral
NWT Health and Social Services
Out-of-Province Referral
Nunavut Department of Health
For acute or emergency presentations of Sudden Sensorineural Hearing Loss (Idiopathic), call 911 first. The receiving emergency department coordinates urgent transfer to the nearest hospital hyperbaric programme through the relevant provincial transfer network (CritiCall Ontario at 1-800-668-4357, BC Patient Transfer Network, EHS Nova Scotia, or equivalent). For diving-related emergencies, the Divers Alert Network (DAN) emergency hotline is 1-919-684-9111.
Untreated pneumothorax is the only absolute contraindication, because trapped intrathoracic air expands on decompression and can cause tension pneumothorax. Concurrent treatment with bleomycin (oxygen-induced pulmonary fibrosis risk) and disulfiram (interference with antioxidant defences) are also contraindicated. Relative contraindications, weighed against expected benefit on a per-patient basis, include severe chronic obstructive pulmonary disease with bullous lung disease, uncontrolled seizure disorder, claustrophobia (manageable in monoplace chambers and with behavioural strategies), recent middle-ear or sinus surgery, and uncontrolled hypertension. Because of the time-sensitive nature of ISSNHL, treatment should not be delayed for minor relative contraindications that can be managed concurrently. Severe ear barotrauma at presentation may require placement of a tympanostomy tube before HBOT can proceed; this is a routine outpatient procedure that takes only a day or two to arrange and does not generally cost the patient meaningful treatment-window time.
As soon as possible. The treatment window is up to 14 days from onset, with best results when treatment begins within the first 7 days. Sudden hearing loss should be evaluated as a medical urgency, not a routine appointment. See an ENT specialist or go to the emergency department promptly. The time from symptom onset to first hyperbaric session is the single most important factor in the likelihood of meaningful hearing recovery.
No treatment guarantees hearing recovery in ISSNHL. About one-third of patients recover spontaneously without any treatment, and recovery is influenced by many variables including time to treatment, severity at presentation, and underlying mechanism. The published evidence shows HBOT combined with corticosteroids produces a substantially higher rate of clinically significant hearing improvement than corticosteroids alone, especially in severe and profound losses, and especially when started early. The decision is based on probability and risk, not certainty.
Yes, at hospital-based hyperbaric programmes under provincial health insurance. ISSNHL is the most recently added Health Canada-recognised hyperbaric indication. OHIP covers treatment at the three Ontario hospital programmes. Alberta Health (code 13.99I) covers treatment at Misericordia Edmonton and Foothills/AJECCC Calgary. MSP covers Vancouver General Hospital. RAMQ covers the two Quebec hospital programmes. MSI, MCP, and Saskatchewan Health each cover their respective hospital programmes. Most Canadian programmes prioritise ISSNHL referrals because of the time-sensitive nature.
Corticosteroids (oral or intratympanic) are the standard first-line treatment and are usually started by the referring otolaryngologist before HBOT begins. Published evidence shows HBOT combined with corticosteroids outperforms corticosteroids alone, particularly for severe and profound hearing losses (greater than 60 dB PTA at presentation). The two are not alternatives; they work through different mechanisms and are typically used together in Canadian practice.
Standard course is 10 to 20 sessions, delivered five days per week over two to four weeks, at 2.0 to 2.5 ATA for 90 minutes per session. Audiometry is repeated at the midpoint and at the end of the course. Cases showing continued improvement at the standard endpoint can be extended to 30 sessions. Cases showing no measurable response by session 10 to 12 are typically discontinued.
The published evidence shows the strongest benefit when HBOT is started within 7 days of onset, with diminishing benefit through the 14-day window. After 14 days, the probability of meaningful recovery from HBOT falls substantially. Canadian programmes often still offer HBOT for severe and profound hearing losses presenting late, particularly when other treatment options have failed, but with appropriately tempered expectations. Discuss your specific timeline and severity with the hyperbaric medicine team.
Tinnitus that accompanies acute ISSNHL often improves alongside hearing recovery during the HBOT course; this is a consistent finding in the published trials. HBOT for chronic isolated tinnitus that is not associated with acute hearing loss is not a recognised indication, has weaker evidence, and is not typically covered by provincial health insurance.
You change into cotton scrubs, enter the chamber, and lie down (in a monoplace) or sit in a recliner (in a multiplace with multiple patients). Pressurisation takes five to ten minutes and feels like the descent in an aircraft. Most people clear their ears with the same technique used in flying. During the 90-minute treatment phase you breathe pure oxygen, often through a hood or mask. Decompression takes another five to ten minutes. Most patients describe the sensation as warm and quiet.
The most common side effect is ear barotrauma during pressurisation, which is managed with pressure-equalisation techniques and resolves between sessions. In rare cases of recurrent severe ear barotrauma, a tympanostomy tube can be placed; this is a routine outpatient procedure. Other relatively common effects are temporary near-sightedness during the course (vision usually returns to baseline within a few weeks of stopping), fatigue, and rare confinement anxiety. Serious complications are uncommon at the 2.0 to 2.5 ATA pressures used for ISSNHL.
Yes, in nearly all cases. There is no general restriction on driving after a routine outpatient HBOT session for ISSNHL. Some patients feel mild fatigue for the first several sessions, in which case a passenger driver or alternate transport is reasonable until you know how you respond.
Yes; hyperbaric oxygen reaches both inner ears equally during treatment, but the rationale and the published benefit relates only to the affected ear with acute hearing loss. The contralateral (unaffected) ear is not changed. Most ISSNHL is unilateral.
Speak with an otolaryngologist (ENT specialist) urgently after the audiogram confirms sudden sensorineural hearing loss. The ENT typically initiates oral or intratympanic corticosteroids and refers to the nearest hospital hyperbaric programme. Most Canadian programmes prioritise ISSNHL referrals for next-available consultation, given the 14-day treatment window. If your ENT is unsure of the referral pathway, the Hamilton General Hospital and Toronto General Hospital hyperbaric medicine teams accept direct consultation requests in Ontario; equivalent direct routes exist in other provinces.
Private hyperbaric clinics typically charge $175 to $350 per session depending on chamber type, duration, and clinical complexity. A 15-session course can therefore total $2,500 to $5,500 out-of-pocket. Some private extended health plans cover specific indications when accompanied by a physician referral; confirm with your plan administrator before booking. Coverage at hospital-based programmes is fully publicly funded for ISSNHL across all 11 hospital programmes nationwide.
The Canada Hyperbarics verified directory at canadahyperbarics.ca/facilities/ lists all 11 hospital programmes alongside their phone numbers, websites, and current chamber status. Coverage details for every province are at canadahyperbarics.ca/hbot-coverage-canada/. Because ISSNHL has a 14-day treatment window, calling the nearest hospital programme directly is often faster than waiting for a routine referral; most programmes accept ENT-to-HBOT direct consultation.