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  • AutorenbildMichael Mutter

Pressure equalisation in fresh and saltwater

Middle ear problems often lead to difficulties in pressure equalisation, are the most common reasons why dives are cancelled or aborted, and can lead to middle ear barotrauma (MEBt) causing symptoms such as ear pain, hearing loss and vertigo. Understanding the effects of repetitive diving on pressure equalisation and Eustachian tube (ET) function is critical to improving diving safety. Two studies compared the effects of diving in warm salt water with those in cold fresh water.

Elphinstone. Foto: Patrick Oswald

The Eustachian tube function test (ETFT) is a diagnostic tool for assessing the function of the ET. By inserting a probe into the ear canal that changes the air pressure in the ear canal, it measures how the eardrum reacts to changes in pressure. The measurements are taken before and after a pressure equalisation (Valsalva) manoeuvre and after swallowing. This involves measuring how much the eardrum moves at a certain pressure. If the mobility of the eardrum improves after pressure equalisation, this signifies good function of the ET. Conversely, a decline in the mobility of the eardrum after a Valsalva maneuver means that the function of the ET is impaired.


The studies

Study 1 investigated the influence of repeated diving in freshwater on pressure equalisation. It was conducted in two freshwater lakes in Nordhausen, Germany, and involved 23 recreational divers over three consecutive days. The divers performed 144 dives. The function of the ET was assessed with the ETFT.


There was a significant decrease in ET function over the three days of diving, indicating increasing difficulty in pressure equalisation of the middle ear. Less experienced divers had more difficulty equalising pressure and suffered more MEBt than experienced divers.


In warm salt water, pressure equalisation improved within days.

Study 2 investigated the same in warm salt water. It was conducted with 28 recreational divers on six consecutive days in the Red Sea. The divers completed 437 dives.


Here, ET function improved in the first 3 days, indicating improved pressure equalisation during these repetitive dives. In this study, less experienced divers were also more likely to suffer MEBt.


Equalise the pressure in small depth intervals - especially in cold water

Conclusion

Warm salt water seems to have less of an adverse effect on pressure equalisation in the middle ear than cold fresh water. It even improved during the first days of the diving holiday. The results clearly show how important it is to take into account environmental factors in diver´s training. Equalising pressure frequently, in small depth increments and taking time for the descent and ascent are the most important precautions to prevent middle ear barotrauma. This is particularly true for diving in cold fresh water.

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