Throughout life, our senses can let us down: hearing loss, vision, smell. Sometimes it happens very early, sometimes it’s quite late, but somehow we get to the doctor’s appointment. One of such specialists is an otorhinolaryngologist. It will be he who will understand the causes of the ailment.
Impedanceometry: what is it?
Impedansometry is an instrumental diagnostic method that helps determine the location and nature of hearing impairment. With it, you can get information about the condition of the auditory tube, cochlea, middle ear, as well as the nerves that innervate them.
This method allows you to identify diseases such as perforation of the eardrum, tympanosclerosis, obstruction of the auditory tubes, otitis media, otosclerosis and others.
Acoustic impedancemetry is an automatic measurement of the shear of acoustic conductivity in the middle ear when the pressure of the air column and the influence of sound change. The main value studied is acoustic admittance, or the conductivity of the structures of the outer and middle ear and their resistance to sound.
Tympanometry
Acoustic impedancemetry includes the measurement of sound conductivity after a change in air pressure. This is called tympanometry. The equipment registers a change in admittance when the pressure rises to two hundred millimeters of water and decreases below -400 millimeters.
Admittance depends on how large the difference is between the pressure in the external auditory meatus and the middle ear. The highest value of this indicator is recorded when the pressure is the same. On the timpogram, this moment is shown as the highest peak. An increase or decrease in pressure gives characteristic changes in the curve. Normally, it should look like the letter "L". A dysfunction of the middle ear changes the amplitude and shape of the tympanogram.
Study of the ventilation function of the auditory tube
Impedanceometry - what is it? This is a way to comprehensively examine the organ of hearing for its reduction or distortion. One of the reasons may be a violation of the functions of the auditory tube. Its overlap is caused by the growth of adenoid vegetation, splitting of the plate of the hard palate, cancer of the nose and mouth, and swelling of the mucous membrane. In children, violations of the patency of the auditory tubes are sometimes observed due to a decrease in tissue elasticity or impaired muscle function of the palatine curtain.
Ear impedanometry to determine the patency of the auditory tube is divided into three stages:
- Verification check. It is produced at normal pressure on both sides of the eardrum.
- The Valsalva Experience. An increased pressure is artificially created in the nasopharynx, and the patient is asked to close his mouth and nose. With normal pipe traffic, the highest value on the tympathogram (peak) will coincide with the moment of greatest pressure.
- Toynbee Experience. Fixing the ventilation capabilities of Eustachian tubes at low pressure. For this patient, they are asked to take a sip, having previously closed their mouth and nose.
Reflexometry
In order to check if there is a contraction of the stirrup muscle (it stretches the eardrum) after exposure to sounds, acoustic impedancemetry is used. How is this procedure carried out? The ear is exposed to noise of varying intensity and volume to check for the presence of an acoustic reflex.
In healthy people, the threshold of this reflex is in the range from sixty to ninety decibels. The change in the tension of the eardrum is recorded on both sides, even if the sound came in only one ear. This reflex is unconditional.
There are two ways to carry out this procedure:
- Ipsilaterally when sound is isolated in the ear that needs to be examined.
- Contlaterally, if the noise is directed to the ear, which is not currently being examined.
For reflexometry, sounds with a frequency of five hundred, one thousand, two thousand and four thousand hertz are used, as well as broadband noise.
Diagnostic value of the procedure
Why is impedancemetry necessary? What is it and why is it carried out? This relatively simple procedure allows the patient to detect conductive and sensorineural hearing loss, damage to the seventh or eighth pair of cranial nerves, and the brain stem. The study is non-invasive, painless and accessible to any patient, regardless of his age and well-being.
Diagnostic criteria for sensorineural hearing loss are the following situations:
- the acoustic reflex is observed at a noise level of less than fifty decibels;
- from fifty to eighty decibels the reflex is recorded in proportion to the amplification of sound;
- after eighty decibels, the reflex is absent.
Acoustic reflexometry does not give results with conductive hearing loss, which allows you to use this feature to differentiate it from sensorineural. The defeat of the facial nerve gives a reflex on the contralateral side, but its absence - on the affected. And in case of dysfunction of the auditory nerve, there is no reflex from either the affected ear or the healthy side.
Esophagus impedanometry
Esophageal impedanometry: what is it? This is a way to determine muscle contractions of the walls of the esophagus, as well as the passage of fluid and gases through it. It is based on measuring the resistance between two electrodes, which are introduced into different sections of the digestive tube. Along with this study, acidity is measured.
The procedure allows you to determine the type of reflux disease (acidic, neutral or alkaline) and its structure (gas or liquid). Diagnostic criteria for GERD (gastroesophageal reflux disease) is a decrease in pH to four or lower, but modern studies refute this theory. Therefore, daily impedancemetry of the esophagus was of great importance.
To do this, a thin probe is inserted through the nose through the nose, on which the sensors are located at the same interval. This device allows you to register the motility of the esophagus and the acidity of the contents that fall into it from the stomach.