Oxygen & Hyperbaric - Pressure risks
Ear, sinus, lung and oxygen safety
Last updated 30 September 2026. How we write this .
Ears are the weak point in a hyperbaric chamber: in one large study over four in ten patients had some ear injury, mostly minor. Lungs are rarely hurt, but an untreated collapsed lung rules treatment out.
Start here Ears are the weak point in a hyperbaric chamber: in one large study over four in ten patients had some ear injury, mostly minor. Lungs are rarely hurt, but an untreated collapsed lung rules treatment out.
By the end, you will understand Why do ears hurt as the chamber pressurises? How common is ear barotrauma, and who gets it? What about sinuses and teeth? Key words used in this lesson Hyperbaric Above normal atmospheric pressure. Hyperbaric oxygen therapy involves breathing oxygen in a pressurised chamber, which increases the amount dissolved in the blood. Full plain-English glossary
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The part of the body most likely to be hurt in a hyperbaric chamber is the middle ear, and most of that damage is minor. Sinuses and teeth are affected less often. Serious lung injury is rare in screened patients, but an untreated collapsed lung is the one condition that rules treatment out completely. Separately, breathing concentrated oxygen under pressure can irritate the lungs and, rarely, trigger a seizure.
Why do ears hurt as the chamber pressurises?
Behind each eardrum is a small pocket of air, the middle ear. A narrow passage called the Eustachian tube links it to the back of the nose. As chamber pressure rises, the air in the middle ear is squeezed into a smaller space and the eardrum is pulled inwards. Swallowing or yawning normally opens the tube and lets air in to balance things. If the tube stays shut, because of a cold, swelling or simply anatomy, the eardrum stretches and the lining of the ear can bleed.
Doctors grade the damage by looking at the eardrum with an otoscope, the lighted scope used in a GP surgery. On the modified Teed scale, grade 0 is normal, 1 is redness or an inward-pulled drum, 2 is slight bleeding, 3 is heavy bleeding in the drum, 4 is blood behind the drum and 5 is a hole, or perforation.
How common is ear barotrauma, and who gets it?
Very common, if you count the mild grades. At SUNY Upstate Medical University in New York, Marvin Heyboer's team reviewed 236 patients who had 4,981 treatments. Middle ear barotrauma, meaning injury from a pressure difference, showed up in 43.2% of them. But 84% of those cases were grade 1 or 2. Patients on a breathing tube, who cannot swallow or yawn to equalise, had more of the severe grade 4 injuries. Heyboer's later review found published rates ranging from about 2% to 84%, mostly because studies define an injury differently.
A larger Italian series from Verona followed 5,962 patients between 2003 and 2010 and recorded 549 cases. Most were grade 1 and most were in women over 50. Inflamed nasal passages, especially rhinitis, made injury more likely. Ear problems forced 89 patients to stop treatment, 1.49% of everyone treated.
Predicting who will struggle is hard. At Townsville Hospital in Australia, Katherine Commons and colleagues followed 106 patients. Over their first five sessions, 35.8% developed barotrauma and 10.3% needed tympanostomy tubes, tiny tubes placed through the eardrum to let air pass. The only strong warning sign was a history of difficulty equalising, which raised the odds about elevenfold. Even so, the team could not predict well enough to fit tubes in advance.
How fast the chamber is pressurised matters too. In a randomised trial of 100 first-time patients at the same hospital, a stepped pressure increase led to barotrauma in 48% against 62% with a steady one. That difference could have been chance, but injuries were significantly less severe with the stepped approach.
What about sinuses and teeth?
Sinuses are the second most common site. They drain into the nose through openings much narrower than the spaces behind them. A cold or hay fever can swell those openings shut, trapping air. The result is pressure pain, usually over the forehead. Pain can also come on the way out, when trapped air expands and cannot escape. Heyboer's review puts nosebleeds from sinus barotrauma at about 1 in 10,000 treatments, and treats an active cold as a reason to postpone non-urgent treatment.
Teeth can hurt too. Tooth squeeze happens when a pocket of air sits under a filling or inside an infected tooth and changes size with pressure.
Can a chamber damage your lungs?
Lung injury works the other way round from ear injury. The risk comes during decompression, when chamber pressure falls and any trapped gas expands. In healthy lungs, air simply flows out. Problems arise when air is trapped, for example in asthma with active wheezing, chronic obstructive pulmonary disease (COPD), or bullae, which are thin-walled air blisters in damaged lung. If the expanding air ruptures lung tissue, it can leak into the chest or into the arteries, where it can cause stroke-like symptoms. Heyboer's review says this is not expected in people without lung disease, which is why screening focuses on lung history.
A pneumothorax, air trapped between the lung and the chest wall, is different. If it has not been drained, it is an absolute contraindication, a firm reason never to treat. As pressure falls, that pocket expands and can become a tension pneumothorax, pressing on the heart and the other lung. The same physics explains UK diving advice: the Oxford Pleural Unit tells patients never to scuba dive after a pneumothorax unless it has been surgically repaired.
Even a drain may not be enough. A 2026 case report from Costa Rica described a 37-year-old woman with a thin pigtail drain in her chest who developed breathing and circulation problems during decompression. Bench tests showed these narrow drains let gas out too slowly when chamber pressure changes.
What does concentrated oxygen do to the lungs and brain?
Breathing high-pressure oxygen for long enough irritates the lining of the lungs. The first sign is a tight, sore feeling behind the breastbone when breathing in, and the most air you can breathe out after a full breath gradually falls. Heyboer's review says this is not expected with routine daily treatment, and symptoms clear within one to three days. A 2019 Israeli study measured lung function in 88 adults before and after 60 daily sessions, with regular short breaks breathing air. It found no meaningful fall in lung function. Nearly all of them, 94.3%, had no lung disease to begin with.
The brain is the other target. The French physiologist Paul Bert first linked high-pressure oxygen to seizures in 1878. Warning signs such as twitching, a fixed stare, nausea, dizziness or changes in hearing and vision appear in fewer than half of cases, so staff cannot rely on them. Risk rises with higher pressure, carbon monoxide poisoning, low blood sugar, an overactive thyroid and brain tumours. Units build in air breaks to reduce the risk, although Heyboer notes this benefit has not been directly proven. The seizure stops once the oxygen level breathed is lowered.
The heart matters as well. Heyboer notes a small risk of fluid building up in the lungs in people whose heart pumps weakly. Two studies put it at 1 in 1,000 and 1 in 4,500. The review advises a heart scan, an echocardiogram, before treatment for anyone with a history of heart failure.
Where are the gaps in the evidence?
Almost all of these figures come from hospital units that examine ears, review lung and heart history and watch every session. They describe screened patients, not anyone who walks into a chamber. Studies also disagree on how to count an ear injury, so any single percentage should be read alongside its definition.
During or after a session, call 999 for chest pain, severe breathlessness, collapse or a seizure. For ear pain that persists, discharge from the ear, hearing loss or facial pain that does not settle, contact your GP or NHS 111.
This lesson is general education about pressure and oxygen safety, not medical advice. Whether hyperbaric treatment is suitable for any individual is a decision for a specialist hyperbaric doctor.
Related in this classroom The studies behind this page Hyperbaric oxygen therapy: side effects defined and quantified - Advances in Wound Care, 2017Middle ear barotrauma in hyperbaric oxygen therapy - Undersea and Hyperbaric Medicine, 2014Middle ear barotrauma during hyperbaric oxygen therapy: a review of occurrences in 5,962 patients - Undersea and Hyperbaric Medicine, 2019A prospective analysis of independent patient risk factors for middle ear barotrauma in a multiplace hyperbaric chamber - Diving and Hyperbaric Medicine, 2013Incidence of middle ear barotrauma in staged versus linear chamber compression during hyperbaric oxygen therapy: a double blinded, randomized controlled trial - Undersea and Hyperbaric Medicine, 2017Tension pneumothorax during hyperbaric oxygen therapy with pigtail pleural catheter: a case report and experimental flow analysis - Undersea and Hyperbaric Medicine, 2026Hyperbaric oxygen therapy effects on pulmonary functions: a prospective cohort study - BMC Pulmonary Medicine, 2019Pneumothorax: information for patients - Oxford University Hospitals NHS Foundation Trust, Oxford Pleural UnitSources for this classroom
Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.