[1] Unequalised ambient pressure increase during descent causes a pressure imbalance between the middle ear air space and the external auditory canal over the eardrum, referred to by divers as ear squeeze, causing inward stretching, serous effusion and haemorrhage, and eventual rupture.
Tympanic rupture during a dive can allow water into the middle ear, which can cause severe vertigo from caloric stimulation.
[3][4] Barotraumas of descent are caused by preventing the free change of volume of the gas in a closed space in contact with the diver, resulting in a pressure difference between the tissues and the gas space, and the unbalanced force due to this pressure difference causes deformation of the tissues resulting in cell rupture.
[5] Barotraumas of ascent are also caused when the free change of volume of the gas in a closed space in contact with the diver is prevented.
Collapse of a pressure resistant structure such as a submarine, submersible, or atmospheric diving suit can cause rapid compression barotrauma.
This can cause the round or oval window to rupture outwards, allowing leakage of perilymph into the middle ear.
This is usually passively released by the Eustachian tube, but in some cases it does not function correctly causing the eardrum to bulge and possibly rupture outward.
Depending on the actual symptoms presented, such conditions could include: otitis media, otitis externa, cerumen impaction, inner ear decompression sickness, caloric stimulation, benign paroxysmal positional vertigo (BPPV), vestibular neuronitis, Ménière's disease, acoustic neuroma, and possibly others.
[2] If there is sensorineural hearing loss or vertigo after exposure to a large change in ambient pressure or a change of breathing gas, the possibility of concurrent barotrauma and inner ear decompression sickness (IEDCS) should be considered, because the symptoms can be very similar, and IEDCS is treated with recompression and hyperbaric oxygen.
The a risk of stretched or burst eardrums, can be reduced by any of a variety of methods to let air into or out of the middle ears via the Eustachian tubes.
[2] If inner ear barotrauma and decompression sickness can be excluded, treatment may include any combination of short term use of nasal decongestants, intranasal steroid sprays and antibiotics for secondary infections.
Some cases are due to simple ambient pressure change and Eustachian tube dysfunction at the time, while others may be partly the consequence of a less obvious underlying condition.
If this happens, pressurization should be stopped and if necessary, reversed sufficiently to allow the Eustachian tubes to be opened more easily, and the middle ear to be cleared.
In urgent clinical hyperbaric treatment, an emergency needle myringotomy or placement of tympanostomy ventilation tubes may be required.
[13] All symptoms should be resolved before diving or flying recommences, including healing of any perforations of the eardrum, and equalisation must be possible,[1] with no abnormal sounds, and hearing is normal.