Inner ear decompression sickness

Inner ear decompression sickness, (IEDCS) or audiovestibular decompression sickness is a medical condition of the inner ear caused by the formation of gas bubbles in the tissues or blood vessels of the inner ear. Generally referred to as a form of decompression sickness, it can also occur at constant pressure due to inert gas counterdiffusion effects.^[1]

Usually only one side is affected, and the most common symptoms are vertigo with nystagmus, loss of balance, and nausea. The symptoms are similar to those caused by some other diving injuries and differential diagnosis can be complicated and uncertain if several possible causes for the symptoms coexist.

First aid is breathing the highest practicable concentration of normobaric oxygen. Definitive treatment is recompression with hyperbaric oxygen therapy. Anti-vertigo and anti-nausea drugs are usually effective at suppressing symptoms, but do not reduce the tissue damage. Hyperbaric oxygen may be effective for reducing oedema and ischaemia even after the most effective period for reducing the injury has passed.

IEDCS is often associated with relatively deep diving, relatively long periods of decompression obligation, and breathing gas switches involving changes in inert gas type and concentration. Onset may occur during the dive or afterwards. IEDCS is a relatively uncommon manifestation of decompression sickness, occurring in about 5 to 6% of cases. The most commonly used decompression models do not appear to accurately model IEDCS, and therefore dive computers based on those models alone are not particularly effective at predicting it, or avoiding it. There are a few rule of thumb methods which have been reasonably effective for avoidance,^[2] but they have not been tested under controlled conditions.