There are 3 main parts to the human ear. The outer ear
is the part you see including the hole that goes into the head to the ear
drum (tympanic membrane). The middle ear starts on the other side of the
ear drum and is a hollow space that is about 1/2" in diameter. The inner
ear consists of fluids and solids. Since the outer ear is open to the water
there is little concern for pressure-related injuries in it. There is no
gas in the inner ear usually so the same is true for that. The middle ear
is a gas space and is subject to compression and expansion in accord with
Boyle's law.
On one side of the middle ear is the ear drum. It is
a flexible membrane. On the other side is a small tube, the eustachian tube,
which connects to the throat above where the back of the mouth is. So, there
you have it: Go down in the water and the middle ear tries to contract. The
ear drum is pushed inward by the high pressure of the water in the outer
ear. The discomfort turns to pain as the ear is being damaged.. As the pain
increases more damage is done. If the situation does not change the ear drum
could rupture allowing cool water to enter the middle ear. That will cool
down the inner ear's semicircular canals. They provide you with orientation.
The diver gets dizzy and loses the ability to distinguish between going up
and down. This is not a pleasant experience underwater!
It is important to keep the pressure
inside the middle ear the same as the ambient water
pressure! This will prevent ear barotrauma
(baro=pressure-related; trauma= injury). It is also known as, "Middle Ear
Squeeze." The eustachian tube is the key. Before the diver descends air should
be forced up the eustachian tube to open it up and add pressure to the middle
ear. It is best to descend feet first (head up). As the diver descends more
air should be forced up the eustachian tube as water pressure is
added to the outer ear. This may not always be easy because the eustachian
is not totally open in the throat. Air has to be gently forced up the tube.
That is best done with a valsalva maneuver: Block the nose, put the tongue
against the roof of the mouth, and GENTLY blow into the nose.
With a mask the nose may be blocked using
both thumbs at the bottom, or, if there is a nose piece, just pinch the
nostrils. After the valsalva the ears should feel normal.
If they don't "clear" stop descending. Go up a little and try the valsalva
again. Do not descend unless the ears are clear.
When you feel pain, damage is being done! If you feel pain you have gone
too deep and should ascend immediately.
The
eustachian tube
is almost closed where it joins the throat. That is why it is difficult to
get air to go into it and then up into the middle ear. If the pressure in
the throat gets too great, and the pressure in the middle ear has not been
increased the eustachian
tube may close completely and not allow any air to enter it.
That is why it is important to push air into the middle ear before going
down even a few feet. But this has to be gentle. Trying too hard to force
air into the middle ear may have the same affect as going too deep before
trying to "clear the ears." Some divers are so persistent in trying to force
air into the middle ear they actually shut down the entrance of the
eustachian tube,
just as if they went too deep before trying to clear the ears. The valsalva
MUST BE GENTLE! If you hear a crackling sound that indicates the eustachian
tube has opened.
A Case in Point: A diver did a
back roll off a boat in the Caribbean. He had too much weight on his belt
and no air in his BC. His descent was rapid and he could not clear his ears.
There was a lot of pain in both ears. Finally at about 25 feet he was
able to do a forceful valsalva. Either the stirrup bone in the middle ear,
or the greater pressure in the inner ear caused the round window to rupture.
Inner ear fluid flowed into the middle ear. The diver was dizzy for years
and orientation was hampered.
Many divers resort to decongestants
prior to diving to reduce any mucus covering the eustachian tube, and to
shrink the membranes around the tube to open it up. It usually works. However,
if the decongestant wears off during the dive it is possible for mucus to
build up again. This could lead to a reverse block, which is explained
below. It is also not wise to use nasal decongestants day after day.
There are other methods in getting
air to go up the eustachian tube. Yawning and swallowing, not so easy to
do underwater, and not as successful with most divers as the valsalva is,
can stretch the muscles in the throat which will open the end of the eustachian
tube allowing high pressure air to enter the middle ear. Chewing gum on an
airplane accomplishes the same thing. Holding the nostrils and making the
sound of the letter "K" sometimes works.
Reverse blocks occur when air gets
into a space on the descent but cannot get out on the ascent. It can happen
in the ear, lung, tooth, sinus, and stomach. In the ear it might happen if
mucus is in (or forced into) the middle ear. The air might pass freely by
the mucus on the way down , but when the diver ascends the mucus could act
as a plug. If the diver continues to ascend the ear drum could rupture outward.
In this case, prevention would be to not forcefully do a valsalva that could
send mucus up the eustachian tube. Treatment would be to descend if pain
is felt on the way up, and then ascend very slowly to allow the air to escape
without pain. Some divers have found that if a valsalva is done it sometimes
pushes the mucus block aside. All of this is good reason to avoid running
low on air in your scuba tank!
It has been thought an ear plug,
similar to those worn by swimmers, could be inserted in the outer ear in
order to prevent pressure on the ear drum. This is foolish. As a diver descended
with an ear plug it would be forced into the ear by the water pressure. That
would be a serious problem! Since the plug would move into the ear the pressure
would still increase so the middle ear squeeze would not have been
avoided.
On occasion divers experience a lightheaded, dizzy feeling
while ascending. It is caused by the ears not decompressing equally. One
ear may clear easily as the diver goes up and the other may be partially
blocked. This ascent vertigo usually goes away in less than 1 minute after
the diver stops ascending or reaches the surface.
In
the unlikely event the diver has serious barotrauma to one or both ears it
is imperative professional medical advice is obtained in order to prevent
possible permanent damage resulting in hearing loss!
Ear infections
are one further consideration in diving. For that matter, whenever you get
water in your ears there is a chance an infection may occur. The water can
be as clean as distilled or from a filthy sewer pipe. It's the water that
causes the problem, not the quality of the water.
Water causes
the wax in the outer ear to be removed. The more wax, the more water it will
take to remove it. If you keep your ears very clean then it does not take
too much water to cause an infection. When the wax is removed the pH of the
skin will be changed by water contact and it will support bacteria that are
just waiting to make you miserable. If the pH becomes too high (alkaline)
bacteria will multiply and create the infection known as "Swimmer's Ear."
Once this happens it's time to visit the doctor, go on antibiotics, and stay
out of diving for at least 2 weeks!
Divers and
swimmers MUST prevent Swimmer's Ear. Religiously, it is important to keep
the bacteria from gaining hold. There are at least 2 methods to do that.
After each day of swimming, diving, showering, etc. either alcohol or acid
must be put in the outer ear. Rubbing (Isopropyl) alcohol will do 2 things:
Dry out the ear and kill bacteria. Boric acid, or dilute acetic acid, will
keep the skin acidic and that will prevent the ear from becoming infected.
THIS MUST BE DONE AFTER EVERY DAY OF WATER ACTIVITIES! If you do not have
either the alcohol or the acetic acid use white wine. It contains both. If
an infection begins neither the alcohol or the acids will do anything to
stop it unless you follow a regimen that I cannot publish in this on-line
book
