Patient Safety
Is hyperbaric oxygen therapy safe? Risks, side effects, and who should not have it
Clinical hyperbaric oxygen therapy (HBOT) is a safe, established medical treatment when it is delivered in a clinical-grade chamber by trained staff. This page sets out the real risks and side effects, who should not receive it, and how medical HBOT differs from mild or home chambers, in the Canadian context. It is educational information, not medical advice; discuss your own situation with a physician.
Is hyperbaric oxygen therapy safe?
Hyperbaric oxygen therapy is generally safe when delivered in a Health Canada-licensed clinical-grade chamber under physician supervision. The most common side effects are temporary: middle-ear barotrauma (pressure-related discomfort or fullness, managed by ear-clearing techniques), transient nearsightedness that resolves within weeks of stopping treatment, and occasional sinus discomfort. Rare serious risks include oxygen toxicity seizures (approximately 1 to 3 per 10,000 sessions at clinical pressures) and chamber-related pneumothorax expansion. The only absolute contraindication is untreated pneumothorax; concurrent bleomycin chemotherapy and concurrent disulfiram are treated as effectively absolute at most programmes, though the UHMS classifies them as relative. Hospital programmes and provincially accredited private clinics follow detailed pre-treatment screening protocols.
What are the side effects of hyperbaric oxygen therapy?
Common side effects (occurring in roughly 1 in 5 to 1 in 10 patients) are middle-ear barotrauma during compression, sinus pressure or congestion, transient claustrophobia in monoplace chambers, and short-term myopia (nearsightedness) that develops over a long course and reverses within weeks of finishing. Less common are dental barotrauma if an existing filling has trapped air, fatigue, and reversible cataract progression in patients having very long courses. Serious adverse events (oxygen seizures, chamber-related pneumothorax) are uncommon at clinical pressures and well-managed by trained chamber operators.
Who should not receive hyperbaric oxygen therapy?
The only absolute contraindication to HBOT is untreated pneumothorax (trapped air in the chest expands on decompression and can cause tension pneumothorax); concurrent bleomycin chemotherapy (oxygen-induced pulmonary fibrosis risk) and concurrent disulfiram (interferes with superoxide dismutase, the enzyme that neutralises hyperbaric-oxygen-generated free radicals) are treated as effectively absolute at most programmes, though the UHMS classifies them as relative. Relative contraindications include severe haemodynamic instability requiring continuous high-dose vasopressor titration, uncontrolled seizure disorder, severe COPD with bullous lung disease, recent middle-ear or sinus surgery, and uncontrolled claustrophobia. Pregnancy is not a contraindication; HBOT is used for severe carbon monoxide poisoning in pregnant patients.
Can I receive hyperbaric oxygen therapy while pregnant?
Pregnancy is not a contraindication to hyperbaric oxygen therapy. HBOT is in fact the standard of care for severe carbon monoxide poisoning in pregnant patients, where the foetus is at higher CO risk than the mother due to foetal haemoglobin's slower CO-clearance kinetics. For elective and chronic indications, treatment during pregnancy is decided case-by-case with the referring obstetrician and the hyperbaric unit; routine elective indications are usually deferred until after delivery unless the clinical benefit clearly outweighs the unknown long-term foetal exposure.
Is hyperbaric oxygen therapy claustrophobic?
Some patients experience transient claustrophobia, particularly in monoplace chambers (single-person acrylic cylinders). Most hospital programmes and many private clinics have multiplace chambers (larger walk-in rooms accommodating multiple patients plus an inside attendant) which feel less confined. Strategies that help: pre-session breathing exercises, watching video content piped in via porthole-viewing monitors, opting for multiplace chambers when available, and a brief familiarisation session before the first treatment. Severe untreated claustrophobia is a relative contraindication; discuss with the hyperbaric medicine team before booking.
What is the difference between hyperbaric oxygen therapy and oxygen bars or mild HBOT?
Clinical-grade hyperbaric oxygen therapy delivers 100 percent oxygen at 2.0 to 2.8 ATA inside a Health Canada-licensed chamber. Oxygen bars and "mild" or "soft" hyperbaric chambers operate at 1.3 ATA or less, sometimes with ambient air rather than concentrated oxygen, and are not Health Canada-licensed clinical-grade medical devices. The clinical evidence base supporting HBOT specifically references pressures of 2.0 ATA and above; lower-pressure protocols do not produce the same dissolved-oxygen physiology. Provincial health plans cover treatment only at hospital programmes operating clinical-grade chambers.