■ What is eustachian tube?  Why is it important?  ■

Eustachian tube

 An eustachian tube is a pipe which connects an ear and a nose, and there is about 3.5 cm by adult.
Although this is usually closed, when we swallow spit or yawn, it is opened, and has balanced the atmospheric pressure of the outside of the eardrum, and an inner side.

 The eardrum will be taut by work of an eustachian tube

The room of the space which has auditory ossicle by the inner side of the eardrum is called drum cavity. Since air has accumulated here, the eardrum vibrates and sound is transmitted. In order to vibrate well, it is necessary to stretch the eardrum taut.
For that purpose, according to change of outside pressure, pressure in a drum cavity needs to change similarly. It leads outside by an auditory tube.


Let’s think the time of taking an airplane.


If it becomes an altitude of 10,000 meters, atmospheric pressure will become low although it is the inside of an airplane. That is, although the outside of the eardrum has low atmospheric pressure, the inside of a drum cavity is still the same pressure as the time of being on the ground.
As it is on anime, the eardrum swells outward. Ear rings and it is hard to hear the sound.
Then if we swallow the spit or chew the gum, , an auditory tube will open, and the air in an airplane flows into a drum cavity from a mouth, and pressure of a drum cavity turns will be the same pressure as the outside of the eardrum. And we will be able to hear like before.


Animator   Prefectural Nichinan hospital  Clinical laboratory Chief engineer  Rika Yabuoshi

 Let’s imagine when you dive deeply by a submarine


If we dive into the sea 10 m, twice as much pressure as this will be received in the bod
If we dive into the sea 20 m, the pressure will increase three times. Power works toward a drum cavity from the outside of the eardrum, and it dents the eardrum inside. If we swallowed spit or it yawn, an auditory tube will open, the air in a submarine passes along an auditory tube, and it goes into a drum cavity. The eardrum returns to the initial position and we can hear the sound normally.

外耳道 :an external auditory canal,鼓膜 : an eardrum,鼓室 : a drum cavity,内耳 : an internal ear,耳管 : an auditory tube

There is a close relation to otitis media. Let’s think about it.

The origin of exudative otitis media

When a state in which pressure in a drum cavity is lower than the atmospheric pressure of the external world continues chronically, the exudative otitis media happens. The big cause is because the original work of an auditory tube of the eardrum making it easy to freshen the air in a drum cavity and to vibrate stops succeeding.
Those are the case that auditory tube has a problem itself, and the cases that an auditory tube may become narrow by the pressure from the auditory tube outside, or the opening of an auditory tube is closed.

 If the state where ventilation in a drum cavity cannot fully be performed continues for a long time, the air in a drum cavity will be absorbed by the surrounding membrane, and will become negative pressure gradually. As a result, the eardrum is pushed on the atmospheric pressure of the external world, and is dented inside.
With only this, hearing decreases, and we will be aware of feeling of fullness in the ear
And soon, the thick liquid (percolation liquid) will be secreted from the membrane of the drum cavity which fell into deficiency of oxygen someday
This accumulates in a drum cavity, and since a motion of the eardrum gets still worse, condition of being hard of hearing increases.


The concrete causes of exudative otitis media

Although there are many causes auditory tube does not pass well, mostly, it is because cilia, which discharges the accumulating liquid in the direction of a nasal cavity, does not work well.
As one cause which is often in a child term, the pharyngeal tonsil (generally called adenoids) in the end of a nasal cavity may enlarge, therefore it may plug up the entrance of an auditory tube.
(right figure)

And, in the case where there are chronic sinusitis, allergic rhinitis, etc. from the first, since the membrane of the circumference of an auditory tube becomes swollen, an auditory tube becomes thin, or by adult, the same condition happens in the tumor (it is sometimes malignancy) which occurred to the circumference of an auditory tube.

How is acute otitis media differed from?

Acute otitis media (correctly acute purulent otitis media) is that bacteria which are in the back and the throat of a nose in connection with cold (acute upper respiratory inflammation) go into a drum cavity through an auditory tube, breeds here, and causes inflammation to mucosa of tympanic cavity.
As a result, a lot of pus are accumulated, and this may stimulate the eardrum from an inner side, and a strong pain arises.
 Exudative Otitis media is not pus and it is that water (exudate) accumulates gradually as mentioned above, and it has the feature that makes no pain including a pain like acute otitis media.

But, although the bacteria in pus have become extinct with the antibiotic since an antibiotic came to be widely used for the medical treatment of acute otitis media in recent years, the state where the pus itself will change to a sterile liquid and it will remain in a drum cavity often came to be seen.
It is the same as the disease state of the exudative otitis media described so far, and  the imperfect medical treatment of acute otitis media results in exudative otitis media.


In reverse, if bacteria invade in a drum cavity from an auditory tube conversely owing to cold etc. when exudative otitis media exists from the first, bacteria will increase quickly in the percolation liquid which has accumulated in the drum cavity, and percolation liquid will change to pus. And, the situation of shifting to acute otitis media as a result is often seen.

That is, it can be said that they have a very close relation of sometimes shifting to a mutual state although acute otitis media and exudative otitis media are completely different disease condition.

Is prognosis of exudative otitis media?

The present condition is that the special-virtue medicine with the action which reduces exudate and makes an auditory tube function normalize is hardly developed yet, and it is only a subsidiary effect. And in the meantime, the medical treatment of exudative otitis media needs to perform combining with various kinds of cures.
Anyway, progress and medical treatment of exudative otitis media have many these things for a long period of time, and the perseverance of a doctor, a patient, and a guardian and their cooperation are indispensable.
However, for many most exudative otitis media diagnosed infants, the condition of disease is getting better by 10 or 12 years old, and hearing ability is stabilized and normalized.
Since the patients need not be hospitalized for a long time, we would like to ask especially guardians to understand and cooperation to work on the treatment slowly and carefully without not getting impatient but giving up on the way.