Impact Of Scuba Diving On The Human Ear
Equalising The Ears While Descending On A Scuba Dive
Jan 1, 2009
The ear has three sections:
Outer: lobes, external ear canal
Middle: separated from the outer ear by the eardrum and contains small auditory sound bones. It is connected to the throat by the eustachian tube.
Inner: semi-circular canals used for balance, and the nerve end that connects to the brain.
Sound waves enter the external ear canal, vibrate the eardrum and the small auditory bones. These bones vibrate against the inner ear which sends auditory signals to the brain.
Ear Squeeze
Ear squeeze is caused when a diver descends creating a pressure difference across the eardrum between the outer and middle ear. The pressure must be the same, or equalised.
Pressure difference forces the eardrum to bulge inwards from the higher pressure towards the lower pressure. This causes increasing pain until eventually the eardrum will burst; resulting in severe pain, ringing in the ears and possibly blood in the external ear canal.
Equalisation of pressure is achieved via the eustachian tube. The tube must open to allow the higher pressure (in the throat) to flow up the eustachian tube into the middle ear. This equalises pressure across the eardrum and is usually referred to as the ear “popping”.
Equalising
The eustachian tube is kept closed by small muscles in the throat. To open these muscles, the scuba diver must yawn, swallow or move the jaw.
Sometimes, opening the eustachian tube is not enough and a diver may need to force air up the tube. This is where the diver pinches the nose and blows against the closed nose and mouth. Called the “Valsalva” technique, it is named after a scientist in the 18th century.
It must not be forceful as the eardrum can rupture.
Problems With Not Equalising
A diver can have problems equalising if the small muscles in the end of the eustachian tube don’t open. The deeper the diver goes, the harder it is to open these small muscles as the pressure difference works to keep them closed. This is overcome by slowing the descent, or ascending slightly, and equalising often.
A diver should continually equalise during descent with the jaw movement, rather than waiting until the pressure is greater and needing the Valsalva technique.
Blocked Eustachian Tubes And Scuba Diving
The eustachian tubes can be blocked by mucus build-up from a cold or infection. In these situations, the diver should not attempt scuba diving as equalisation becomes difficult and damage could occur.
Medications such as nasal sprays can be used to clear minor mucus blockages, but should be used with caution. Some sprays may wear off quicker when under increased pressure. Tablet decongestants can lead to drowsiness.
Problems On Ascent
If the eustachian tube is closed during the ascent, a “reverse ear squeeze” can occur. The pressure in the inner ear is higher than the pressure in the throat, causing the eardrum to bulge outward.
The diver must perform a reverse Valsalva technique. Instead of blowing against the closed nose, the diver must inhale against the closed mouth. This should pull the air out of the inner ear and into the throat.
Experienced Divers
Equalising without pinching the nose can be a sign of an experienced diver. They are continually equalising by moving their jaw or forcing air up the eustachian tube by blowing against the mask without taking the specific action of holding the nose.
Like managing the risk of the Bends, equalising the ears is needed due to the pressure changes when descending on a scuba dive. Equalising must be done well and often to avoid injury, and for safe and enjoyable diving.
