Travel Reference
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Figure 8-2. Anatomy of the ear and eustachian tube
1
Occasionally a traumatic injury causes a blood clot beneath the skin of the external por-
tion of the ear. If the clot is large enough to cover one-third or more of the ear, it can cause
a permanent cauliflower ear if allowed to persist. Such clots should be drained to avoid
this type of scarring. The skin should be cleaned and swabbed with an antiseptic. Then one
or more one-eighth-inch (3 mm) incisions should be made and the blood expressed with
gentle pressure. Removal of all the blood is not necessary and would probably aggravate
the underlying injury.
Barotrauma
The middle ear and the paranasal sinuses are lined by thin mucous membranes and are
filled with air. These chambers have narrow openings to the nose or throat through which
air moves to equalize the pressure within the chamber with atmospheric pressure. The
opening into the middle ear, the eustachian tube, is much longer than the openings into the
sinusesandismoreeasilyobstructed(
Fig.8-2
).Asaresultbarotraumaismorecommonin
the ear.
As atmospheric pressure decreases during an ascent to altitude, air usually leaves these
chambers without difficulty. However, increasing atmospheric pressure during a descent to
lowerelevationstendstoclosethechamberopenings.Activemeasuressuchasswallowing
or yawning may be required to open the eustachian tube. A light “pop” is often heard as
the pressure is suddenly equalized. However, when the difference in pressure between the
middle ear and the atmosphere is 90 mm Hg or more, the eustachian tube can no longer be
openedbyswallowing.Inairthispressuredifferentialrequiresachangeinaltitudeofabout
3750 feet (1150 m) near sea level and can only develop when descent is rapid, as occurs
in aircraft or rarely in automobiles on steep mountain roads. However, under water, such
pressuredifferencescandevelopwithadescentofonlyafewfeet,particularlynearthesur-
face. Colds or nasal allergies cause swelling of the mucosa around the eustachian tube or
the ducts into the nasal sinuses, which can partially obstruct the openings and hinder pres-
sure equalization.
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