HBOT risks & safety.
The honest safety guide. Absolute contraindications, strong cautions, common minor effects, oxygen toxicity, and medication interactions. Everything we screen for — and why.
01
Absolute contraindications
These conditions rule out HBOT entirely — not just at R1SE, but anywhere. Tell our team if any of these apply.
Untreated pneumothorax
A collapsed lung that hasn't been clinically resolved. Pressurisation can dramatically worsen a pneumothorax and trigger tension pneumothorax. If you've ever had spontaneous pneumothorax, even years ago, please tell the team — we'll need imaging clearance before booking.
Active bleomycin chemotherapy
Bleomycin (used in some lymphoma and germ-cell-cancer regimens) causes pulmonary toxicity that is dramatically worsened by hyperoxic exposure. The lung damage can be fatal. Active bleomycin treatment, or completion within the last 12 months, is an absolute exclusion.
Untreated middle-ear pathology
Active middle-ear infection, untreated chronic Eustachian tube dysfunction, or recent ear surgery (within 8 weeks) prevent safe equalising and risk middle-ear barotrauma. Postpone HBOT until your GP or ENT has confirmed the ear is fully healed.
Implanted devices not certified for hyperbaric use
Some pacemakers, neurostimulators, and insulin pumps are not certified for pressure beyond 1 ATA. Bring your device documentation; the team will check the manufacturer's pressure rating. Many modern devices are HBOT-compatible up to specified limits.
02
Strong cautions — requires team review
These don't rule out HBOT, but they require a discovery conversation, possible specialist clearance, and sometimes a modified protocol.
Severe or unstable cardiovascular disease
Recent myocardial infarction (within 3 months), unstable angina, severe uncontrolled hypertension, or congestive heart failure all warrant cardiology input before HBOT. The pressure shift is gentle but adds load to a compromised cardiovascular system. Stable, well-controlled cardiac disease is usually fine with monitoring.
Severe COPD or bullous lung disease
COPD with significant air-trapping or visible bullae on imaging is a relative contraindication — pressure changes can cause bullae to expand or rupture. Mild-to-moderate COPD is usually compatible with HBOT under team supervision; severe disease requires imaging and respiratory specialist input.
Pregnancy
Elective wellness HBOT is generally avoided in pregnancy. There are specific medical indications where HBOT is delivered during pregnancy (under hospital supervision), but the wellness setting isn't appropriate. If you're pregnant or planning pregnancy, please discuss with our team and your obstetric provider.
Uncontrolled seizure disorder
Hyperoxic exposure can lower the seizure threshold in some individuals. Well-controlled epilepsy (no seizures in 12+ months on stable medication) is usually fine at wellness HBOT pressures. Uncontrolled or recent-onset seizure disorder needs neurologist input before booking.
Severe claustrophobia
Mild-to-moderate claustrophobia is usually tolerated, particularly in the soft-shell. Severe claustrophobia (you cannot tolerate an MRI or small enclosed space) may make HBOT impractical. We always offer a short orientation session to test before committing to a protocol.
Current chemotherapy other than bleomycin
Many chemotherapy regimens are compatible with HBOT — some are even used alongside it medically (radiation-induced tissue damage). But interactions vary. We require oncologist clearance for anyone in active chemotherapy.
03
Common minor effects (well-tolerated)
These happen often, resolve quickly, and are not cause for concern — but worth knowing about so you're not surprised.
Ear pressure during descent
The most common HBOT experience. The eardrum compresses inward during pressurisation; gentle equalising (swallow, yawn, soft Valsalva) clears it. Roughly 1 in 50 first-timers find their first descent uncomfortable until they get the rhythm. By session 2–3, almost everyone has it.
Mild barotrauma
If equalising fails, the eardrum can become inflamed or, rarely, perforated. The team slows descent to prevent this; tell us immediately if anything feels stuck or painful. A perforated eardrum is a temporary contraindication that resolves with healing (usually a few weeks).
Post-session fatigue
A small minority of members feel mildly tired or sleepy after a session, particularly early in a protocol. This typically reflects the parasympathetic shift and clears with rest. Members frequently report unusually deep sleep the night of a first session.
Temporary myopia
Extended HBOT (typically 20+ sessions) can cause a small, reversible shift in vision (slight myopia). The cornea changes hydration under prolonged hyperoxia. Glasses prescriptions can shift by 0.5–1 diopter during a long protocol and revert within weeks of completion. Worth flagging if you're due an eye test; rebook for after the protocol.
Dryness in mouth, throat or eyes
Dry-air breathing for an hour can leave mucous membranes briefly dry. Hydration before and after the session is the simple fix. We provide water inside the chamber for ongoing sipping.
04
Oxygen toxicity — why air breaks exist
Extended high-pressure pure oxygen exposure carries a small risk of oxygen toxicity. The Hadanny air-break structure is the standard mitigation.
Pulmonary oxygen toxicity
Long exposure to 100% O₂ at pressure can inflame lung tissue. The dose required is well above typical wellness sessions, but it's why we use air breaks (5 min on air every 20–25 min on O₂) during sessions at 1.5+ ATA. Cumulative exposure across a 60-session protocol stays well within safe limits.
CNS oxygen toxicity
Very rare; typically only seen at pressures of 2.4+ ATA on extended sessions, which is beyond standard wellness use. Symptoms can include facial twitching, visual disturbance, or seizure. R1SE protocols stay at or below 2.0 ATA precisely to keep this risk negligible.
Why air breaks are non-negotiable
Beyond safety, the air breaks are part of the active mechanism. The hyperoxic-hypoxic paradox — cycling between very high oxygen and brief intermittent air — triggers HIF-1α signalling that drives regenerative outcomes. Skip the air breaks and you lose much of the active ingredient as well as adding risk.
05
Medications that need a flag
A few medications interact with hyperoxic conditions in ways worth flagging on intake.
Bleomycin (absolute)
Already covered above — this is an absolute contraindication, not a flag.
Doxorubicin / cisplatin
These chemotherapies can interact with hyperoxic conditions. Generally requires oncologist clearance; sometimes a longer interval since last dose.
Disulfiram (Antabuse)
Alcohol-aversion medication that interacts with hyperoxia and can lower the seizure threshold. Postpone HBOT until 24 hours clear of the last dose.
Insulin (diabetic patients)
HBOT can transiently lower blood glucose. Type 1 diabetics on insulin should check blood sugar pre- and post-session for the first few visits and may need a small carbohydrate snack pre-session. The team will discuss specifics at intake.
Steroids (high-dose corticosteroids)
Generally compatible but can affect inflammation signalling. Worth flagging on intake so the team can monitor response.
Photosensitising medications
Not an HBOT-specific issue but a flag if you're also using R1SE's red light therapy. Some antibiotics (tetracyclines, fluoroquinolones), retinoids, and certain anti-inflammatories increase photosensitivity.
Common questions
Honest screening. Sensible sessions.
We screen carefully on intake and review before every session. If HBOT isn't safe for you, we'll tell you — and we'll happily refund any booking that turns out to be a non-starter.
Continue Reading
More from the R1SE HBOT Library
HBOT Knowledge Hub
Every hyperbaric oxygen page on the R1SE knowledge library.
ReadThe Science of HBOT
Telomere lengthening, cognitive enhancement, neuroplasticity — every claim cited.
ReadThe Benefits of HBOT
Cellular regeneration, recovery, anti-aging signals.
ReadConditions HBOT Treats
Post-concussion, long COVID, ulcers, stroke, fibromyalgia.
ReadHow to Use HBOT
Pressure, duration, frequency — from beginner to protocol-grade.
ReadTypes of Hyperbaric Chamber
Hard- vs soft-shell. 1.3 vs 2.0 ATA. Monoplace vs multiplace.
Read