HBOT Safety Guidelines

Overview

HBOT has an excellent safety profile when delivered by trained staff with proper screening. The most common adverse event — middle-ear barotrauma — is minor and preventable. Serious adverse events are rare. The two mechanisms that drive the safety framework are pressure (barotrauma, pneumothorax risk) and oxygen (seizures, pulmonary toxicity at high cumulative exposure).

Absolute Contraindications

• Untreated pneumothorax — the one true absolute contraindication. Pressurisation can convert a stable pneumothorax to a tension pneumothorax during decompression. Chest imaging is required if any history is suspicious. Treated pneumothorax (with chest tube removal and documented re-expansion) is not a permanent contraindication but requires physician assessment.

Relative Contraindications

These require individual physician assessment and often protocol modification, but are not absolute bars to treatment:

• Severe COPD with air trapping or bullae — risk of pulmonary barotrauma during decompression. Pulmonary function testing and chest imaging guide decision-making.
• Recent eye surgery — particularly cataract (within 2–3 months) and retinal procedures. Discuss with ophthalmologist.
• Uncontrolled epilepsy — increased CNS oxygen toxicity seizure risk at pressures above 2.0 ATA. Well-controlled epilepsy on stable medication is often manageable.
• Uncontrolled fever — lowers seizure threshold; defer HBOT until fever resolves.
• Severe claustrophobia — manageable with anxiolysis, multiplace chamber choice, or gradual conditioning sessions.
• Active bleomycin therapy — lifetime contraindication due to risk of pulmonary fibrosis.
• Active doxorubicin (and related anthracyclines) therapy — relative contraindication during the active treatment cycle due to cardiotoxicity concerns.
• Cisplatin, mafenide acetate, disulfiram — all have specific interactions with HBOT; physician review required.
• Pregnancy — treatment case-by-case for emergency indications. Carbon monoxide poisoning in pregnancy is a positive indication for HBOT.
• Recent myocardial infarction (within 6 weeks) — generally defer non-emergency HBOT. Cardiology consultation for high-risk patients.
• Ejection fraction < 35% — HBOT can increase cardiac afterload transiently; assess cardiac reserve.
• Pacemaker / ICD — most modern devices are rated for HBOT pressures, but device manufacturer specifications must be verified.
• Severe sinus disease or acute upper respiratory infection — risk of sinus barotrauma; defer until resolved.

Pre-Treatment Screening

1. Hyperbaric physician consultation. Confirm indication, review medical history, and document informed consent.
2. Ear equalisation assessment. The most common adverse event is middle-ear barotrauma. Patients unable to equalise reliably may need myringotomy tubes before starting a course.
3. Chest imaging (CXR or CT). Review for pneumothorax, severe bullae, pleural effusion, or significant pulmonary pathology. Required for every patient at most UHMS-accredited facilities.
4. Medication review. Flag chemotherapy (particularly bleomycin), disulfiram, mafenide acetate, cisplatin, and medications that lower seizure threshold.
5. Blood glucose check (diabetic patients). HBOT lowers blood glucose; monitor pre- and post-session. Target pre-session glucose > 120 mg/dL.
6. Pregnancy test (women of childbearing age, when clinically indicated).
7. Baseline functional/cognitive assessment for neurological protocols — provides a reference for interim and post-course comparison.
8. Dental assessment for radiation injury protocols — carious teeth may become symptomatic during pressurisation.

Barotrauma Prevention

Middle-Ear Barotrauma (Most Common)

Occurs in 2–15% of patients depending on screening and technique. Caused by failure to equalise pressure in the Eustachian tube during compression. Symptoms range from mild pain to haemorrhagic tympanic membrane rupture.

Prevention

• Teach Valsalva, Toynbee, and Frenzel equalisation techniques before the first session.
• Compress slowly (typically 1–2 psi/min equivalent); pause compression if a patient reports ear discomfort.
• Pre-treat with pseudoephedrine or intranasal decongestant for patients with mild Eustachian tube dysfunction (with physician approval).
• Myringotomy tubes for patients unable to equalise despite training.

Management

• If barotrauma occurs, pause the course until the eardrum has healed or myringotomy tubes are placed.
• Minor haemotympanum typically resolves in 2–4 weeks.
• Oral decongestants and nasal steroids may be prescribed during healing.

Sinus Barotrauma

Less common than ear barotrauma but similar mechanism — inability to equalise paranasal sinuses during pressure change. Usually self-limited; defer treatment during acute upper respiratory infection.

Pulmonary Barotrauma

Rare but serious. Occurs almost exclusively during decompression when expanding gas cannot escape the lung (bullae, air trapping, breath-holding during ascent). Prevention: thorough pre-treatment screening for COPD and bullae, patient education to breathe normally throughout decompression, and controlled decompression rate.

Oxygen Toxicity Prevention

CNS Oxygen Toxicity (Paul Bert Effect)

Characterised by generalised tonic-clonic seizures. Rare at ≤2.4 ATA; incidence approximately 1 in 10,000 sessions. Risk factors include higher pressure, prolonged O₂ exposure without air breaks, fever, hyponatraemia, hypoglycaemia, and some medications (ACE inhibitors, aspirin at high dose).

Warning Signs (VENTIDC)

• Visual disturbance (tunnel vision, scintillating scotomata)
• Ear ringing / tinnitus
• Nausea
• Twitching (facial, lip, or limb muscles)
• Irritability or anxiety
• Dizziness
• Convulsion

Prevention & Management

• Scheduled 5-minute air breaks every 20–30 minutes of oxygen breathing in protocols at or above 2.0 ATA.
• If prodromal symptoms occur, immediately switch to chamber air (or 21% O₂ via mask).
• If seizure occurs, do not decompress during the seizure — oxygen toxicity seizures are self-limited and decompression during a tonic phase risks pulmonary barotrauma.
• Resume decompression once the tonic phase has resolved and the patient is on air.
• Seizure is not a bar to future HBOT once the acute episode is resolved and the protocol is adjusted.

Pulmonary Oxygen Toxicity (Lorrain Smith Effect)

Cumulative effect of prolonged high-FiO₂ exposure. Rarely relevant to standard 40- or 60-session courses but monitored in extended protocols. Measured in Unit Pulmonary Toxic Dose (UPTD) — cumulative exposure above approximately 600 UPTD begins to produce measurable reduction in vital capacity.

• Standard 40-session HBOT courses accumulate well below the toxicity threshold.
• Clinical relevance primarily to divers with repeated extended-duration exposure.

Chamber & Facility Safety

Fire Safety

Oxygen dramatically accelerates combustion. The infamous 1967 Apollo 1 fire and historical chamber fires (Milan 1997, Lauderdale 2009) led to the current NFPA 99 (National Fire Protection Association) standards governing hyperbaric facilities:

• No open flames or sparks.
• No electronics inside monoplace chambers unless specifically certified for hyperbaric use. This includes cell phones, hearing aids with batteries, and medical devices.
• Cotton-only clothing. Synthetic fabrics can accumulate static charge; wool and polyester have been implicated in multiple incidents.
• No petroleum-based products on skin (lotions, hair products, nail polish, aerosol sprays). Water-based alternatives only.
• Chamber air deluge/suppression systems maintained to NFPA 99 specifications.
• Facility staff trained annually in emergency decompression, fire suppression, and medical response.
• Grounding straps for all monoplace chamber occupants.

Infection Control

• Chamber interior cleaned and disinfected between patients per facility protocol.
• Dedicated hoods, masks, and tubing for multiplace patients; cleaned per manufacturer specifications.
• Patients with open wounds covered appropriately before pressurisation.
• Hand hygiene practised by staff before and after each patient contact.

Emergency Decompression

In the event of a medical emergency requiring urgent chamber exit, facilities follow a decompression protocol that balances safety with speed:

• Routine decompression: 1–2 psi/min equivalent.
• Emergency decompression: faster rates per facility SOP, with staff attending to barotrauma risk.
• Multiplace chambers have a trained chamber attendant who performs in-chamber medical response before decompression is attempted.

Population-Specific Considerations

Paediatric HBOT

• Children typically well-tolerate HBOT; the main challenge is ear equalisation in young children unable to perform Valsalva.
• Myringotomy tubes considered proactively for children under 5.
• Multiplace environments preferred so a parent or clinician can be in-chamber for reassurance.
• Standard pressures (2.0–2.4 ATA) are used; dose adjustment not typically required by weight.
• Fire safety considerations identical to adults — cotton clothing only, no electronics.

Elderly Patients

• Cardiac screening particularly important; HBOT transiently increases afterload.
• Baseline cognitive assessment advised, as cognitive changes during a course may be clinically relevant.
• Hearing loss and claustrophobia more common; multiplace environments may be better tolerated.
• Dentition review for patients with restorative work before extended courses.

Diabetic Patients

• HBOT lowers blood glucose via multiple mechanisms. Monitor pre- and post-session.
• Pre-session target glucose > 120 mg/dL to prevent in-chamber hypoglycaemia.
• Patients on insulin may need dose adjustment during the course.
• Educate on hypoglycaemia symptoms; snacks available for post-session.

Patients with Implanted Devices

• Pacemakers, ICDs: Most modern devices are rated for HBOT pressures. Verify with the device manufacturer's hyperbaric compatibility data sheet before treatment.
• Insulin pumps: Generally not compatible with HBOT; remove before pressurisation.
• Cochlear implants: Most modern cochlear implants are HBOT-compatible; verify per device.
• Internal drug delivery systems (baclofen pumps, etc.): Device-specific; consult manufacturer.
• Pulmonary artery catheters, Swan-Ganz: Must be depressurised or removed per critical-care HBOT protocols.

Common Adverse Events (Rates)

In-Session Safety

• Two-way intercom communication maintained throughout the session.
• Vital signs monitored continuously for medically complex patients; intermittently for routine cases.
• Blood glucose checked before and after each session in diabetic patients.
• Compression and decompression at controlled rates (typically 1–2 psi/min equivalent).
• Air breaks scheduled per protocol for 2.0+ ATA treatments.
• Emergency medications and equipment accessible outside the chamber at all times.
• Scheduled check-ins with the patient during long sessions (reorientation, comfort, ear equalisation).

Patient Education Before Starting a Course

• Explain the physiology — why pressure matters, why 100% oxygen is used, why air breaks occur.
• Teach equalisation techniques; practise on dry land before the first session.
• Clothing and skincare restrictions (cotton only, no lotions or hair products on treatment days).
• Dietary guidance — avoid carbonated beverages immediately pre-session; have a light meal 1–2 hours prior.
• Alcohol and recreational drug restrictions during a course.
• Expected course length and attendance commitment.
• Signs and symptoms to report to staff (ear pain, visual disturbance, nausea).
• Realistic expectations about outcomes, with awareness of individual variability.

Reporting Adverse Events

UHMS-accredited facilities maintain adverse event reporting as part of quality assurance. Serious adverse events should be reported both internally and, where applicable, to:

• FDA MedWatch — for device-related events in the US.
• UHMS Patient Safety Program — anonymised reporting that contributes to international data.
• Manufacturer — for device-specific events (pacemaker interactions, chamber malfunction).

Safety disclaimer: This page summarises general safety principles and is not a substitute for facility-specific protocols, physician training, or UHMS certification. All HBOT must be delivered by trained staff under physician oversight. Specific adverse event rates and management strategies may differ from the ranges cited; consult current UHMS guidance and local protocols.