TL;DR: Sudden sensorineural hearing loss is a medical emergency. Hyperbaric oxygen therapy, added to steroid treatment within the first two weeks, is associated with about 2.6 times higher odds of hearing recovery compared with steroids alone. In Canada, HBOT for sudden hearing loss is offered at a small number of hospitals and regulated facilities. Treatment is most useful when started early, so see an ear, nose, and throat specialist the same week your hearing changes.
Sudden sensorineural hearing loss (SSNHL) is a rapid loss of hearing in one or both ears, often noticed on waking up or within a few hours. It is treated as a medical emergency because the chance of recovery drops as time passes. This Canadian patient FAQ explains what SSNHL is, how hyperbaric oxygen therapy (HBOT) fits into care, what the recent evidence shows, and how to access treatment in Canada. Canada Hyperbarics curates this information for patients across the country.
What is sudden sensorineural hearing loss?
Sudden sensorineural hearing loss is a rapid drop in hearing caused by a problem with the inner ear or the hearing nerve. It usually develops in less than 72 hours and most often affects one ear. Many people describe it as muffled sound, ringing (tinnitus), a feeling of fullness in the ear, or dizziness. About 90 percent of cases have no clear cause and are labelled idiopathic SSNHL.
The inner ear has a tiny blood supply from a single artery, which makes the cochlea vulnerable to reduced oxygen, inflammation, or small blood vessel problems. Recent reviews of inner ear anatomy show why even short interruptions of blood flow can damage hearing cells quickly.
Why is sudden hearing loss treated as a medical emergency?
Time matters. Hearing cells in the inner ear can be permanently damaged within days if oxygen and blood flow are not restored. The window where treatment works best is usually the first 14 days, and outcomes are strongest in the first 7 days. After about 4 to 6 weeks, the chance of meaningful recovery falls sharply.
If you notice a sudden change in hearing, do not wait for it to clear on its own. Contact your family doctor, a walk-in clinic, or a hospital emergency department the same day and ask for an urgent referral to an ear, nose, and throat (ENT) specialist. Ask the ENT directly whether HBOT is available in your region.
How does hyperbaric oxygen therapy work for hearing loss?
Hyperbaric oxygen therapy is a medical treatment where you breathe 100 percent oxygen inside a pressurised chamber. The increased pressure dissolves much more oxygen into your blood plasma than normal breathing can, which raises the oxygen reaching tissues with poor blood flow, like the inner ear.
For SSNHL, the main proposed mechanisms are:
- Raising the partial pressure of oxygen inside the cochlea, where hair cells need oxygen to survive
- Improving microcirculation and reducing inner ear swelling
- Reducing inflammation that may damage hearing nerves
- Supporting recovery of damaged but still living cochlear tissue
A 2025 review in Molecular Medicine Reports summarises these mechanisms and notes that HBOT works best when combined with corticosteroids in the early phase of SSNHL.
Does HBOT actually help recover hearing?
The strongest recent evidence says yes, when added to steroids early. A 2025 systematic review and meta-analysis in The Laryngoscope pooled data from 20 studies and 1,687 patients. Patients who received HBOT combined with medical therapy had 2.61 times higher odds of hearing recovery than those who received medical therapy alone (95 percent confidence interval 1.86 to 3.68).
The same review found a benefit whether HBOT was added to systemic steroids alone or to systemic plus intratympanic (ear injection) steroids. The authors note that treatment protocols still vary between centres, so research continues on the best pressure, session length, and number of treatments.
A smaller real-world study published in Undersea and Hyperbaric Medicine in 2024 also found significant audiometric improvement, with pure-tone hearing averages improving from 50.3 to 36.0 decibels after HBOT (Leder Macek and colleagues, 2024).
When should HBOT be started after hearing loss begins?
As early as possible, ideally within 14 days of symptom onset. Studies consistently show better outcomes for people who start HBOT in the first two weeks. After 4 weeks, the benefit shrinks, and after about 6 weeks, most centres no longer offer HBOT as an option for SSNHL.
The U.S. Undersea and Hyperbaric Medical Society (UHMS) lists idiopathic sudden sensorineural hearing loss as an approved indication for HBOT when started within 14 days, and Canadian hyperbaric programs generally follow the same window.
What other treatments are used alongside HBOT?
HBOT is almost never used by itself for SSNHL. The standard medical care in Canada includes:
- Oral steroids (most often prednisone) for 10 to 14 days, tapered down at the end
- Intratympanic steroid injections directly into the middle ear, especially if oral steroids do not help or are contraindicated
- Imaging (MRI of the inner ear and brain) to rule out other causes such as a benign tumour
- Hearing tests (audiometry) before, during, and after treatment to track recovery
HBOT is added when steroids alone do not fully restore hearing, or sometimes from the start in severe cases. A 2023 review in Medical Gas Research describes how HBOT and steroids work together to reduce inner ear swelling and improve oxygen delivery at the same time.
How many HBOT sessions are typical for sudden hearing loss?
Most Canadian centres prescribe 10 to 20 sessions for SSNHL. Each session usually lasts 90 to 120 minutes at a pressure of 2.0 to 2.5 atmospheres absolute (ATA). Sessions are typically delivered once a day, Monday to Friday, over 2 to 4 weeks.
| Typical HBOT protocol for SSNHL | Range |
|---|---|
| Pressure | 2.0 to 2.5 ATA |
| Session length | 90 to 120 minutes |
| Frequency | 5 sessions per week (weekdays) |
| Total sessions | 10 to 20 |
| Course length | 2 to 4 weeks |
| Best window from symptom onset | Within 14 days |
Your hyperbaric physician will tailor the number of sessions to your audiometry results, your overall health, and how quickly hearing improves.
What does a hyperbaric session feel like?
You lie or sit comfortably inside a clear acrylic or steel chamber. As the chamber pressurises, you will feel pressure in your ears, similar to descending in an airplane. The technician will coach you through ear-clearing techniques such as yawning, swallowing, or a gentle Valsalva manoeuvre.
Once at treatment pressure, you simply rest, watch a screen, or listen to music while breathing the oxygen. The technician monitors you throughout. At the end, the chamber is slowly depressurised over several minutes.
Are there side effects or risks?
HBOT is generally safe when delivered by trained staff at hospitals and regulated facilities. The most common side effects are mild and short-lived:
- Ear pressure or pain during compression (the most common issue, usually managed by clearing the ears)
- Temporary changes in vision that resolve within weeks after the course ends
- Sinus discomfort, especially with a cold or allergies
- Fatigue after sessions
Rare but more serious risks include middle ear injury, oxygen toxicity seizures, and pressure-related lung injury. Your hyperbaric physician will screen you before the first session for conditions that may increase risk, such as untreated pneumothorax, certain medications, or recent ear surgery. Patients with rheumatologic disorders may be less likely to respond to HBOT for SSNHL based on observational data.
Is HBOT for sudden hearing loss covered by provincial health insurance in Canada?
Coverage depends on the province and the facility. In several provinces, HBOT for SSNHL delivered in a hospital is covered under the provincial health plan when it is medically necessary and referred by a specialist. The provincial plans by name are:
- Ontario – OHIP
- British Columbia – MSP
- Alberta – AHCIP
- Quebec – RAMQ
- Manitoba – Manitoba Health
- Saskatchewan – Saskatchewan Health
- Nova Scotia – MSI
- New Brunswick – Medicare NB
- Newfoundland and Labrador – MCP
- Prince Edward Island – PEI Health
HBOT delivered at a private clinic is usually paid out of pocket. Some extended health plans cover part of the cost. Ask your ENT and the hyperbaric centre about coverage before starting. You can also review the provincial coverage guide for general information by province.
Where can I get HBOT for sudden hearing loss in Canada?
HBOT for SSNHL is offered at a small number of Canadian hospitals and regulated facilities. Hospital-based hyperbaric units are concentrated in Ontario, Quebec, British Columbia, Alberta, and Nova Scotia. Examples include Sunnybrook Health Sciences Centre in Toronto, where Canadian hyperbaric physicians have written in the Canadian Medical Association Journal about HBOT for SSNHL (Alam and colleagues, CMAJ 2025).
The Canada Hyperbarics directory of hospitals and regulated facilities lists publicly verified Canadian centres with hyperbaric programs. Call ahead to confirm that the facility treats SSNHL and to ask about wait times, since the 14-day window matters.
What happens if I miss the treatment window?
If more than 4 to 6 weeks have passed since your hearing loss began, most centres will not offer HBOT for SSNHL. The evidence does not support meaningful benefit that late. However, other options remain:
- Hearing aids fitted by an audiologist
- Bone-anchored or cochlear implants for severe loss in one ear
- Vestibular rehabilitation if dizziness is part of the picture
- Tinnitus management strategies
Even if HBOT is not an option, an ENT and an audiologist can help you choose the best long-term plan for your hearing and quality of life.
How is sudden hearing loss different from age-related or noise-related hearing loss?
Age-related hearing loss (presbycusis) develops slowly over years and usually affects both ears. Noise-induced hearing loss builds up after repeated exposure to loud sound. Neither is considered a hyperbaric emergency. Sudden sensorineural hearing loss is different because the change happens in hours or days, often in one ear, and the inner ear may still be partly recoverable if oxygen and blood flow can be restored quickly.
Frequently asked questions
Is HBOT a cure for sudden hearing loss?
HBOT is not a guaranteed cure, but the best recent evidence (a 2025 systematic review and meta-analysis of 20 studies and 1,687 patients) shows that adding HBOT to standard medical therapy is associated with about 2.6 times higher odds of hearing recovery than steroids alone. Outcomes are best when HBOT is started within the first 14 days.
Will I need a referral from my family doctor for HBOT?
Yes. Hospital-based hyperbaric programs in Canada require a referral, usually from an ENT specialist after initial assessment. Your family doctor can fast-track an urgent ENT referral. If you go to a hospital emergency department with sudden hearing loss, ask the team directly whether HBOT and an ENT consult are available the same week.
Can I still benefit from HBOT if I waited a week to see a doctor?
Yes. The 14-day window is generous. Hearing recovery is still possible if HBOT begins in the second week, although outcomes tend to be best when started within the first 7 days. Past 14 days, benefit shrinks, and past 4 to 6 weeks most centres no longer offer HBOT for SSNHL.
Does HBOT help if hearing loss is in both ears?
Bilateral sudden hearing loss is uncommon and is investigated for underlying causes such as autoimmune disease, infection, or medication side effects. HBOT may still be considered, but treatment plans are individualised. An ENT specialist and a hyperbaric physician will guide the decision based on the suspected cause and overall health.
Can I drive home after a hyperbaric session?
Most patients drive themselves to and from sessions. Some people feel mild fatigue after treatment and prefer to arrange a ride for the first few sessions until they know how they respond. Vision changes during a course of HBOT can affect glasses or contact lens prescriptions, so let staff know if you notice blurring.
Where can I learn more?
For background on how HBOT works for many other conditions, visit the Canada Hyperbarics general FAQ. The Canadian Undersea and Hyperbaric Medical Association (CUHMA) maintains a list of Canadian hyperbaric programs and educational resources for patients and physicians.
Ready to find a Canadian hyperbaric centre?
If you or a loved one has experienced sudden hearing loss in the last two weeks, speak to an ENT today and ask about HBOT. To find a Canadian centre, browse the Canada Hyperbarics list of hospitals and regulated facilities and call the centre nearest you to check availability.
Medical disclaimer: This content is for informational purposes only and does not constitute medical advice. Always consult a qualified physician or specialist about diagnosis and treatment. Canada Hyperbarics is an independent informational resource and does not provide medical care.