Safety & Contraindications

Absolute contraindications

The single absolute contraindication universally recognised in the hyperbaric medicine literature is untreated pneumothorax. Compression and decompression cycles can convert it to a tension pneumothorax. A treated, stabilised pneumothorax is not an absolute contraindication; the clinical decision must weigh the indication's urgency against pulmonary risk.

Relative or contextual chemotherapeutic concerns: concurrent administration of doxorubicin (cardiotoxicity), bleomycin (pulmonary toxicity), cisplatin (impaired wound healing), and disulfiram (interferes with reactive oxygen species scavenging) is approached cautiously and may be considered an absolute contraindication during active drug exposure.

Relative contraindications

• Severe COPD with carbon-dioxide retention — managed with arterial blood gas monitoring and individual risk-benefit assessment.
• Recent middle-ear or sinus surgery — Eustachian tube dysfunction increases barotrauma risk; ENT clearance and pre-treatment evaluation recommended.
• Active upper respiratory infection or febrile illness — defer treatment until resolution where the indication permits.
• Claustrophobia — managed with pre-treatment counselling, gradual exposure, and chamber selection (multiplace chambers tolerate anxiety better than monoplace).
• History of seizure disorder — increases CNS oxygen toxicity risk; protocol modification (lower pressure, shorter sessions, air breaks) may be required.
• Pregnancy — first-trimester elective HBOT is not advised; emergency indications (carbon monoxide poisoning) override the relative contraindication.
• Optic neuritis history — risk of progression has been described.
• Diabetes — close glucose monitoring required; HBOT can lower blood glucose during sessions.

Adverse events

The Heyboer et al. (2017) systematic review remains the most comprehensive quantification of HBOT side effects in the published literature.

• Middle-ear barotrauma — by far the most common adverse event, typically minor and self-limiting with prompt pressure-equalisation training; severe cases (haemotympanum, perforation) are uncommon.
• Sinus squeeze (barosinusitis) — less common than middle-ear effects; managed with decongestants and slower compression.
• Pulmonary barotrauma — rare but serious; risk is reduced by careful patient selection and exclusion of bullous disease.
• Central nervous system oxygen toxicity — manifests as a generalised seizure during session; rare in modern protocols (≤2.5 ATA, ≤90 min). Standard management is reduction of inspired oxygen, descent to sea level after the seizure ends, and careful re-evaluation.
• Pulmonary oxygen toxicity — cumulative and dose-dependent; relevant on long treatment courses.
• Reversible myopia / refractive change — described in long treatment courses (commonly cited as resolving over weeks to months after the course ends).
• Confinement anxiety — managed with chamber selection, light music, and pre-treatment exposure.
• Hypoglycaemia — in diabetic patients on insulin or sulphonylureas; monitor and adjust as needed.

Pre-treatment screening

Standard pre-treatment screening in HBOT services typically includes:

• Tympanic-membrane assessment and Eustachian function check.
• Sinus history; ENT review where indicated.
• Chest imaging where pulmonary risk factors are present.
• Medication review for chemotherapeutic agents and disulfiram.
• Pregnancy status (where applicable).
• Seizure history.
• Claustrophobia / anxiety screening.
• Diabetic glucose-monitoring arrangements.
• Cardiac assessment in patients with significant coronary or congestive heart disease.

Stop criteria

Treatment should be discontinued or substantially modified in the following circumstances:

• New pneumothorax during a session.
• CNS oxygen toxicity event (seizure) — protocol modification or discontinuation.
• Failure of middle-ear pressure equalisation despite training and ENT input.
• Persistent severe adverse event without identifiable mitigation.
• Patient-led withdrawal due to anxiety or intolerance not manageable through standard supports.
• Concurrent administration of an absolute-contraindication chemotherapeutic agent that cannot be paused.