Hyperbaric Oxygen Therapy Side Effects and Risks

HBOT is safe for most patients when performed by trained medical staff at an accredited facility. But it does carry side effects, and some patients shouldn’t use it at all.

Some side effects are common and mild. Others are rare but serious. And some people shouldn’t use HBOT at all.

Common Side Effects

These side effects happen in many patients. Most are mild and manageable.

Ear barotrauma is the most common side effect. The pressure changes during pressurization and depressurization affect your ears the same way altitude changes do on an airplane. You’ll feel fullness, pressure, or mild pain until you equalize. Your care team will teach you equalization techniques before your first session. Done correctly, most patients tolerate this without problems. Rarely, repeated sessions can cause a temporary change in hearing that resolves after treatment ends.

Temporary myopia (nearsightedness) develops in some patients who complete many sessions. The lens of the eye changes shape with repeated oxygen exposure. This usually reverses within weeks to months after stopping treatment. Tell your eye doctor you’re doing HBOT if you notice vision changes during your course.

Fatigue is common in the first week or two. Your body is adjusting to an unusual level of oxygen. Most patients find this resolves early in the treatment course.

Claustrophobia can be a problem in monoplace (single-person) chambers. If you know you’re claustrophobic, tell your care team before your first session. Options include anti-anxiety medication, slower chamber orientation, or switching to a multiplace chamber if one is available.

Sinus squeeze is similar to ear barotrauma but affects the sinuses. It’s more likely if you’re congested. If you have a cold or sinus infection, talk to your hyperbaric physician before your session. You may need to postpone.

Rare but Serious Risks

These complications are uncommon in properly run programs. But you should understand them.

Oxygen toxicity seizures are the most serious known risk of HBOT. Breathing very high concentrations of oxygen at pressure can, in rare cases, trigger a seizure. The risk is highest at pressures above 3.0 ATA. At standard treatment pressures (2.0-2.5 ATA), oxygen toxicity seizures are rare. If one does occur, it’s self-limiting, meaning it stops on its own when oxygen is removed. Hyperbaric staff are trained to manage this. Long-term neurological harm from an oxygen toxicity seizure is not expected when handled correctly.

Pulmonary oxygen toxicity can occur with very long or very frequent treatment courses. Protocols that include regular air breaks (periods of breathing regular air during a session) significantly reduce this risk.

Pneumothorax (collapsed lung) is very rare. The risk is higher in patients with certain lung conditions, including existing air pockets (bullae or blebs) in the lungs. Most programs require a chest X-ray before starting treatment to screen for this.

Fire is a theoretical risk in any high-oxygen environment. This is why you aren’t allowed to bring electronics or petroleum products into the chamber. Serious fires in properly run, accredited hyperbaric facilities are extremely rare.

Who Shouldn’t Use HBOT

A pre-treatment medical evaluation by a hyperbaric physician is required at all legitimate programs. That evaluation screens for contraindications.

Absolute contraindication: Untreated pneumothorax. Do not enter a hyperbaric chamber if you have an unresolved collapsed lung.

Relative contraindications (these require a case-by-case evaluation, not automatic exclusion):

Active ear infection or eustachian tube dysfunction
Severe COPD with CO2 retention
Certain chemotherapy drugs (doxorubicin, bleomycin, and cisplatin) have known interactions with HBOT and may be contraindicated
History of spontaneous pneumothorax
Some pacemaker models (older devices may not be chamber-compatible)
High fever
Severe congestive heart failure in some cases

Pregnancy is not an automatic contraindication. HBOT is used for carbon monoxide poisoning during pregnancy because the benefit clearly outweighs the risk. For other indications, the risk-benefit discussion with your physician applies.

Claustrophobia isn’t a contraindication, but it does need to be managed before you start.

How Risks Are Managed

Accredited hyperbaric programs have protocols specifically designed to minimize risk.

Before treatment, your hyperbaric physician reviews your full medical history, medications, imaging, and any potential contraindications. That evaluation exists to keep you safe.

During sessions, trained staff monitor you continuously. Air breaks are built into protocols for longer sessions. Pressurization is controlled to allow proper ear equalization.

After completing a course of treatment, your provider will monitor for any lingering effects like vision changes.

The key is choosing an accredited facility with board-certified hyperbaric physicians. Standards from the Undersea and Hyperbaric Medical Society (UHMS) and the American College of Hyperbaric Medicine (ACHM) exist precisely to ensure safe practice.

For more on what to expect during a session, read What to Expect at Your First HBOT Session. For questions about how many sessions you’ll need, read How Many Hyperbaric Treatments Do You Need?.

Frequently Asked Questions

Can HBOT cause a seizure?

Oxygen toxicity seizures can occur but are very rare at standard treatment pressures. The risk is highest at 3.0 ATA and above. If a seizure occurs, it’s self-limiting. Hyperbaric staff are trained to respond. Protocols including air breaks reduce the risk during longer sessions.

Will HBOT hurt my hearing?

The ear pressure changes during pressurization are the most common side effect. With proper equalization technique, most patients tolerate this well. Temporary hearing changes can occur but are rarely permanent.

Can I do HBOT if I have a pacemaker?

It depends on the pacemaker model. Some modern pacemakers are compatible with hyperbaric chambers. Older models may not be. Your hyperbaric physician will evaluate your specific device before clearing you for treatment.

Does HBOT cause vision problems?

A temporary shift toward nearsightedness is common with multiple treatments. It typically reverses within weeks to months after completing your course. Let your eye doctor know you’re undergoing HBOT if you notice any changes during treatment.

Medical Disclaimer: This page is for informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before pursuing any medical treatment.