Barotrauma

In short

A barotrauma is an injury caused by a pressure difference between an air space in the body (ears, sinuses, lungs…) and the surrounding water. On the way down, air is compressed; on the way up, it expands. If the air space cannot equalize, its walls are stretched or squeezed. Most barotraumas can be prevented with simple actions: equalize early and often, never force it, and never hold your breath.

Why it matters

Ear barotrauma is the most common problem in diving, especially for beginners. It is usually minor if dealt with early, but it can damage the eardrum or the inner ear if you force it. Lung overexpansion injury is rarer, but it is one of the most serious diving accidents. Understanding the mechanism helps you adopt the right reflexes from your very first dives.

The principle: Boyle's law

At constant temperature, the volume of a gas is inversely proportional to its pressure. Underwater, pressure increases by about 1 bar every 10 m:

Depth	Absolute pressure	Volume of a balloon filled at the surface
Surface	1 bar	1 l
10 m	2 bar	0.5 l
20 m	3 bar	0.33 l
30 m	4 bar	0.25 l

Between the surface and 10 m, the volume is halved. Between 30 m and 40 m, it only changes by a fifth. The largest volume changes therefore happen near the surface: the first metres of the descent and the end of the ascent need the most attention.

The ears

The middle ear

Behind the eardrum is a small air space, the middle ear, connected to the back of the nose by the Eustachian tube. On the way down, the water pushes on the eardrum: you need to send air into the middle ear to restore the balance. This is equalization.

• Valsalva: pinch your nose, keep your mouth closed and blow gently as if blowing your nose. It is the best known technique; it must stay gentle.
• Frenzel: with your nose pinched, push air towards the back of the throat with your tongue, without blowing from the lungs. It is gentler and takes some practice to learn.
• Voluntary tubal opening and swallowing: swallowing, yawning or moving the jaw opens the tube without pressure. Some divers manage it without pinching their nose.

Good habits

• Equalize from the surface, then every metre at the start of the descent, before you feel any discomfort.
• Descend slowly, preferably feet first, along a line or a slope.
• If you feel discomfort: stop descending, go up one or two metres and try again gently.
• Never force it: if equalization does not work, the dive ends for you. Tell your guide.
• On the way up, air normally comes out by itself. A feeling of blockage on ascent means ascending even more slowly and telling your instructors.

The inner ear

It contains the organs of hearing and balance. Forceful or late equalization can injure it. The signs are dizziness (vertigo), nausea, ringing or hearing loss. They mean ending the dive and getting prompt medical advice.

Other air spaces

• Sinuses: bony cavities in the face, connected to the nose. They usually equalize by themselves, unless they are blocked (cold, allergy). Signs: pain in the forehead or cheekbones, sometimes a nosebleed.
• Mask: the air in the mask is compressed on the way down and can suck the mask against your face (mask squeeze). Regularly breathe a little air out through your nose into the mask. This is why swimming goggles, which do not cover the nose, are not used for diving.
• Teeth: a cavity or recent dental work can trap air and cause pain. See your dentist and tell them you dive.
• Stomach and intestines: gas expands on the way up. Avoid fizzy drinks and heavy meals before diving, and do not swallow air when equalizing.

Lung overexpansion injury

The mechanism

Underwater, you breathe air at ambient pressure. If you hold your breath while ascending, the air in your lungs expands and cannot get out: the air sacs (alveoli) overstretch and then tear. Air can then enter the chest or the bloodstream. This can happen even in shallow water, close to the surface, for example in a pool.

Typical situations

• fast or panicked ascent, for example after running out of air;
• breath-holding, voluntary or reflex (exertion, coughing, cold);
• uncontrolled ascent (over-inflated BCD, lost weights).

The signs

They appear quickly, often as soon as the diver leaves the water: chest pain, coughing, frothy or bloody spit, breathing difficulty, change in voice, but also neurological problems (confusion, weakness in a limb, speech problems, loss of consciousness). It is a life-threatening emergency.

Prevention

• Breathe normally at all times; never hold your breath when scuba diving.
• Control your ascent rate, especially in the last metres.
• If you must ascend without air, breathe out continuously.
• Work on your buoyancy to avoid uncontrolled ascents.

What to do if signs appear

First-aid actions follow the dive supervisor's instructions and your training:

1. End the dive for the person concerned and tell the guide and the dive supervisor.
2. Breathing or neurological signs, or feeling unwell: this is an emergency. Call for help (VHF channel 16 or 196 at sea in France, 112 on land) and give oxygen, by a trained person.
3. Ear or sinus pain, dizziness, hearing loss: do not dive again and see a doctor, ideally an ear, nose and throat specialist or a diving doctor.
4. Only a doctor can decide when you may dive again.

Do not put anything into a painful ear after a dive and do not take any treatment on your own initiative: ask a doctor for advice.

Risk factors

• colds, sinusitis, allergies: swollen airways prevent equalization;
• fatigue and stress, which make your actions less precise;
• descending too fast, without equalizing early enough;
• smoking, which irritates the airways;
• a history of ear or lung problems: tell the doctor who issues your medical certificate.

Key takeaways

• The largest volume changes happen between the surface and 10 m.
• Equalize early, often and gently; never force it.
• Breathe out through your nose into your mask on the way down.
• Never hold your breath while ascending.
• Do not dive with a cold, and see a doctor if any unusual sign appears.

Further reading

The water entry guide covers controlled descents, and the safety guide explains how to call for help. Your federation's and DAN's medical recommendations detail contraindications and what to do.