ANATOMY OF A DIVER
The inner ear
Dr Rosie Stokes sets out the workings of the inner ear , and two forms of damage that can occur to it through diving accidents
The inner ear is a fluid filled compartment containing the cochlea and semi-circular canals . These organs are responsible for hearing and balance , and are not exposed to the ‘ outside world ’ as the compartment contains nerves which connect directly to the brain . Conversely , the middle ear , which it sits adjacent to , is connected to the ‘ outside world ’ via your throat ( and thus nose and sinuses ) via your eustachian tube . In divers , the inner ear can be damaged through two main mechanisms : 1 . BAROTRAUMA : Difficulty equalising the middle ear transmits pressure to the inner ear , which can cause damage or leak of fluid 2 . DECOMPRESSION ILLNESS ( DCI ): Expansion of nitrogen bubbles in the tissues of the inner ear
Inner ear DCI or barotrauma ?
For dive doctors it can sometimes be difficult to distinguish the mechanism of ear pathology , as the ear is a complicated structure and symptoms can be similar for both DCI and barotrauma . A lot can be gained from the history of the dive and the time of onset of symptoms . The average time of onset for an inner ear DCI is 40 minutes from surfacing , whereas barotrauma can be evident either during the dive or immediately after .
BAROTRAUMA : If the diver had ear pain during the dive or had a rapid ascent , then it is likely to be a barotrauma . It is important to recognise this , as putting a diver with a barotrauma into a hyperbaric chamber may make the damage worse ! Barotrauma usually occurs when the diver has a cold or has taken decongestants which have worn off whilst underwater . Alternatively , the diver may not have equalised their ears sufficiently during the
dive . Pressure changes in the middle ear cause damage to the surrounding structure and can be seen as redness or swelling on the ear drum .
Such divers should refrain from diving until this has completely settled , and should seek advice from a dive doctor . If a leak of the fluid from the inner ear has occurred , then the diver is likely to have longer term problems with their ears and may not be able to dive again .
INNER EAR DCI : Also called an audiovestibular bend ; risk factors include deep or repetitive dives and underlying medical conditions such as a PFO ( hole in the heart ). Inner ear DCI has also been associated with mixed gas diving , such as use of trimix . While this is a known risk factor , most cases that we see at DDRC are divers on air or nitrox .
The inner ear becomes injured due to the expansion of nitrogen bubbles in the tissues causing damage to the structures and nerves that control your hearing and balance . The diver may experience symptoms such as changes in hearing , ringing in the ears , nausea / vomiting , and difficulty with balance . Often , the diver will lie down and hold their head still to try to
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minimise this . As stated previously , these symptoms may not be evident immediately and will generally appear , on average , 40 minutes after surfacing . If you recognise these symptoms in yourself or another diver , it is important to start oxygen straight away and to call for medical assistance . Seek advice from a dive-doctor as soon as possible .
EXAMINATION : The patient ’ s neurological system including their eye movements , balance , coordination , and hearing will be examined .
Treatment : If an inner ear DCI is diagnosed then the diver will be treated in a hyperbaric chamber to reduce the size of the nitrogen bubbles . Subsequent hyperbaric oxygen treatments allow any damaged tissue to repair and will be continued daily until the symptoms improve or stabilise .
Following treatment , the diver must refrain from diving for three months and will need to be reviewed by a dive doctor for a fitness to dive assessment prior to returning to the water . It is likely that they will be offered a referral for a PFO ( hole in the heart ) check to screen for this underlying risk factor ( especially if the incident occurred with a relatively conservative dive profile , or if there is a history of migraines with aura ).
Returning to diving
Both an inner ear barotrauma and inner ear DCI can leave the diver with permanent symptoms , which could affect their career or stop them from diving again . They may need to be seen by an ear , nose , and throat ( ENT ) specialist for further input . Keeping your dives conservative and controlled will reduce the risk of a dive injury and will protect your ears . It is much easier to prevent damage than to treat it ! �
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