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Audiometric examination

In clinical otorhinolaryngology, subjective and objective methods of audiometric diagnosis of hearing loss are used.

Subjective ones include threshold tonal audiometry and determination of auditory sensitivity to ultrasounds, as well as suprathreshold tests, speech, noise audiometry, research of noise immunity of the auditory system, spatial hearing, determination of the spectrum and intensity of subjective ear noise.

Threshold tone audiometry can be performed in an extended frequency range, including with the determination of the lower boundary of perceived sound frequencies (UHF).

At suprathreshold tonal audiometry, the following are studied: the differential threshold for the perception of strength (DPS) and frequency (DFH) of sound, the time of reverse adaptation (VOA), the level of uncomfortable volume (UDG), the dynamic range of the auditory field (DSP). One of the tasks of suprathreshold audiometry is the identification of the phenomenon of accelerated increase in volume (FUNG), which is characteristic for damage to receptor cells of the Corti organ.

Objective methods of audiological diagnosis of hearing loss include: impedance audiometry, audiometry for auditory evoked potentials and otoacoustic emission.

Threshold tone audiometry is the most common method of audiological diagnosis. All audiological studies begin with tonal audiometry, so each otolaryngologist must know its methodology and evaluate the results.

Tonal threshold audiometry is carried out using audiometers, which differ from each other in functionality and control (Fig. 1.2.6). They provide a set of frequencies (pure tones) 125, 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000, 8000 and 10000 Hz (in some audiometers there are also frequencies 12000 and 16000 Hz). The sound stimulus of the auditory system is pure tones or noises (narrow-band and broad-band), which are formed in the audiometer using a sound generator. In most audiometers, the stimulus intensity is switched in steps of 5 dB from 0 to 110 - 120 dB by means of an attenuator (intensity regulator).

Fig. 1.2.6.

Audiometers are equipped with a headband with two air telephones, a bone vibrator, a patient button, a microphone and a low-frequency input for connecting a tape recorder (or CD player) for voice audiometry.

An ideal condition for audiometry is a soundproofed room (sound chamber), with a noise background of up to 30 dB. Currently, many portable sound cameras are being produced. In practice, it is possible to conduct audiometry in a normal room, which is not affected by external noise (walking, talking in the corridors, transport on the street, etc.).

The threshold of perception of tone is the minimum sound pressure at which an auditory sensation appears. Research begins with a better hearing ear, and in the absence of asymmetry of hearing, from the right ear. In healthy people, the response time to acoustic signals is 0.1 s, while in older people and the deaf, it increases.

The examinee receives a short, accurate and understandable briefing, and in the process of audiometry, the researcher constantly communicates with the patient through the microphone, making sure that the technique is correctly performed.

First, the sensitivity of the tone is measured at 1000 Hz, then higher tones, and the measurement ends by determining the thresholds of low-frequency tones. Signals are given from 0 dB to a threshold above the threshold for the patient to evaluate the nature of the presented signal. Then the sound volume immediately decreases to an inaudible level, after which a threshold is determined at the level of a weakly audible tone, which is confirmed three times in 5 dB steps using the tone chopper button to exclude adaptation. The values ​​of each sound threshold are plotted on the audiogram.

With asymmetric hearing and listening to the tone with a better hearing ear, clinical masking is performed using narrow-band noise. The term "disguise" means the supply of masking noise to a better-hearing ear in order to turn it off. Many masking methods have been proposed. With the sliding variant of masking (Lehnhardt E., 1987) of air conduction, it is shown when the difference between the thresholds of air conduction worse than the hearing ear and the thresholds of bone conduction better than the hearing ear is 50 dB or more. Bone conduction is masked if the difference between the thresholds of bone and air conduction worse than the hearing ear is 15 dB or more, and the thresholds of bone conduction of this ear are 10 dB or more higher than the opposite. For the initial masking of air conduction, the threshold noise intensity is increased by 20 dB, and for bone conduction, by 10 dB. With continued listening to the tone, the noise intensity increases in steps of 10 dB for air and bone conduction until the tone is perceived worse by the hearing ear. If this does not happen, then it is considered that the tone at the studied frequency is not perceived.

The technique for determining thresholds for bone conduction is similar to that described above. First, lateralization of sounds in the forehead or crown is noted (Weber's experiment) when signals are exceeded by 10-15 dB exceeding the thresholds of bone audibility. The ear is examined first, towards which lateralization of the tone is directed. The bone vibrator, when wearing headphones, is applied with a mass of 500-700 g to the mastoid process. The need for masking with bone audiometry arises much more often than with air.

On tonal audiograms, the vertical lines (ordinates) reflect the intensity in dB, and the horizontal (abscissa) reflect the frequencies in Hz or kHz. It is generally accepted that the threshold curve of air conduction is indicated by a solid line and bone conduction by a dotted line. Data for the right ear is marked in red, and for the left ear, in blue. Masking the air conduction of a better hearing ear is indicated by a thick line, and bone conduction by a zigzag icon. These signs are written in color worse than the hearing ear at the corresponding frequencies and intensities of masking noise on the side of the better hearing ear (Fig. 1.2.7).

Fig. 1.2.7

Deviation of tonal thresholds by an average of ± 10 dB at each frequency is considered normal if air and bone conduction are adjacent and there are no complaints of hearing impairment. With normal visual acuity, the tonal curves of air and bone conduction pass near the zero line or are superimposed on it (Fig. 1.2.8).

? en. 1.2.8

Hearing loss is characterized by a number of typical audiological signs, allowing differential diagnosis between sound-conducting (conductive), sound-perceiving (sensorineural or perceptual) and its mixed forms.

The “ainoiayuay” e? Eaay of air conduction is characteristic of the dysfunction of the sound-conducting apparatus (Fig. 1.2.9), which is the result of the worst audibility of low tones and satisfactory perception of high tones. In this case, the curve at low frequencies drops to 30-50 dB. The bone conduction curve is located close to the threshold zero line and does not fall at low frequencies more than 20 dB, and at high frequencies more than 10 dB. There is a bone-air interval of more than 20 dB.

Fig. 1.2.9

The progression of conductive hearing loss leads to a further increase in the tonal thresholds of air conduction at high frequencies, as a result of which the curve becomes almost horizontal, but does not exceed 60 dB. Mixed hearing loss develops, in which bone thresholds increase to 40 dB at both low and high frequencies, but bone conduction remains satisfactory over the entire frequency range. Between the bone and air conduction curves, a gap of up to 15 dB remains (Fig. 1.2.10).

Fig. 1.2.10

The “ienoiayuay” e? Eaay aicaooiie i? Iaiaeiinoe, yaey? Uayny? Acoeuoaoii ooaoaai aini? Eyoey aunieeo oiiia is characteristic of dysfunction of the sound-receiving apparatus. Ienoiayuay e? Eaay einoiie i? Iaiaeiinoe i? Eea? Eo ee? Eaie aicaooiie i? Iaiaeiinoe. A iaeanoe ieceeo? Anoio ii? Ao iaae? Aaouny einoii-aicaooiue eioa? Aae ai 10 aA. Ia n? Aaieo e aunieeo? Anoioao e? Eaua einoiie e aicaooiie i? Iaiaeiinoe iiaoo neeaaouny eee ia? Anaeaouny (? En. 1.2.11).

? en. 1.2.11

When analyzing tonal audiograms, an age-related increase in hearing thresholds (presbycusis) in air and bone-tissue conductivity is taken into account.

Speech audiometry is performed using an audiometer and a tape recorder connected to it or a special speech audiometer. Various authors have developed tables of different frequency words (Voyachek V.I., Grinberg G.I. et al.), Which are fed into the patient's ear via air phones, a bone vibrator or speakers in a free sound field.

The purpose of the study is to determine the thresholds of sensitivity (discrimination) and speech intelligibility. Speech intelligibility refers to the percentage of correctly named words by the patient to the number transmitted to him along the test path (at least 30 words are transmitted). The intensity of speech recorded on tape is controlled using an audiometer.

There are three main thresholds for speech intelligibility. The threshold of sensitivity corresponding to the lowest intensity of speech at which a person begins to hear a conversation, but does not understand a single word and cannot repeat it. With an increase in the volume of words, speech intelligibility thresholds of 50% and 100% are determined when the patient correctly repeats half the words or all words.

On the speech audiogram (Fig. 1.2.12), levels of speech intensity from 0 to 120 dB with an interval of 10 dB are marked on the abscissa axis, and its intelligibility percentage from 0 to 100% with an interval of 10% on the ordinate axis. On forms, a curve of normal speech intelligibility is necessarily plotted after calibrating a speech audiometer by identifying the above thresholds in at least ten young people (20-30 years old) with normal tonal hearing.

Fig.
1.2.12

With conductive hearing loss, the speech intelligibility curve runs parallel to the normal curve. The threshold of speech sensitivity is separated from that by comparison with the norm by no more than 40-50 dB. The remaining thresholds are separated from the corresponding thresholds of the normal curve by the same decibel as the sensitivity threshold. Speech intelligibility reaches 100%.

With sensorineural hearing loss, the sensitivity threshold is more than 50-60 dB off the norm. The audiogram curve is not parallel to the normal curve, deviated to the right, or has a hook shape. 100% speech intelligibility is often not achieved.

Above-threshold tonal audiometry in the clinic is mainly intended to identify the phenomenon of accelerated increase in volume - FUNG, which consists in the fact that with pathology of the receptor of the auditory system, along with hearing loss, there is an increased sensitivity to loud sounds and a quick spasmodic perception of them. For example, a person hears a sound of 65 dB with his right ear and 15 dB with his left ear. With an increase in the intensity of sound in both ears stepwise by the same amount, a moment comes when the signal is perceived equally loud with both ears, that is, the volume is equalized. However, for a better hearing ear, you have to amplify the sound, for example, by 65 dB, and for a worse hearing one, only 30 dB.

FUNG is detected using the following supra-threshold tests: aeooa? Aioeaeuiiai threshold of sound power (DPS), level of uncomfortable volume (UDG), dynamic range of the auditory field (DSP), volume balance according to Fowler, SISI test - index of sensitivity to short sound rise, etc. FUNG is more often observed with high thresholds of bone conduction (40 dB or more), normal or reduced level of uncomfortable volume and a decrease in the dynamic range of the auditory field, 0.2-0.7 DPS and 70-100% SISI test. It indicates a lesion in the cochlear receptor and is noted for sensorineural and less commonly mixed hearing loss. FUNG, as a sign of receptor hearing loss, is considered in combination with other audiological indicators.

Impedance audiometry is a method of measuring the acoustic impedance of a sound-conducting apparatus of the auditory system (from Latin impedire - to interfere). It allows for differential diagnosis of middle ear pathology (serous otitis media, adhesive otitis media, otitis media, otosclerosis, rupture of the auditory ossicle chain), as well as an idea of ​​the function of pairs VII and VIII of the cranial nerves and brainstem auditory pathways.

Using an impedance audiometer (Fig. 1.2.13), the compliance of a sound-conducting apparatus is studied under the influence of sound wave pressure or a hardware change in air pressure in the ear canal. There are two methods for this: tympanometry and measuring the acoustic reflection of the stapes. Results are recorded on the printer of the device or visually manually. Using the impedance method, the ventilation function of the auditory tube, the stapes mobility in the oval window (Jelle air experiment) and the pressure in the tympanic cavity are also evaluated.

Fig. 1.2.13

Tympanometry consists in recording the compliance of a sound-conducting apparatus with a change in air pressure in the ear canal from 0 to + 300 - 300 mm H2O. On tympanograms, compliance is indicated in arbitrary units - ml or cm3 and the top of the curve is directed upwards. There are 4 main types of tympanograms (Fig. 1.2.14): A, B, C and D, and in the normal tympanogram (A), there are varieties (A1 and A2), the vertices of which are reduced to 3 and 2 ml. The normal tympanogram (A) is characterized by full compliance of the eardrum (conditionally complement up to 5 ml), a high peak of the curve and zero pressure. Type B is characterized by low flexibility of the membrane (complement up to 1-1.5 ml) with a flat top or lack of it, negative pressure or the inability to determine it in the tympanic cavity (secretory, mucous, adhesive otitis, tympanosclerosis, glomus tumor, etc.). Tympanogram C is characterized by almost normal compliance of the sound-conducting apparatus, but its apex is always shifted towards negative pressure (tubootitis, adenoids, etc.). Type D is distinguished by hypersensitivity of the eardrum (complement of more than 5 ml), when the tympanogram apex is not fixed and a plateau is formed due to a decrease in the rigidity of the membrane due to the formation of extensive malleable scars, atrophy of the eardrum, or a break in the chain of auditory ossicles after inflammation and injury.

Fig. 1.2.14

Tympanograms A1 and A2 are noted with otosclerosis. With sensorineural hearing loss, the tympanogram is normal.

The study of the Acoustic reflex is based on recording the contraction of the stapes muscle under the influence of a sound wave coming from an audiometer built into the impedance meter. The nerve impulses caused by the sound stimulus reach the superior olives through the auditory tract, where they switch to the motor core of the facial nerve and reach the stapes muscle. Muscle contraction occurs on both sides. It is possible to register the acoustic reflex of stapes in the stimulated ear (ipsilaterally) or in the opposite - contralaterally. Normally, the threshold of the acoustic reflection of the stapes is about 80 dB above the individual threshold of sensitivity.

With conductive hearing loss, pathology of the nuclei or the trunk of the facial nerve, the acoustic reflex of the stapes is absent on the side of the lesion. With neuroma of the VIII nerve, ipsi and contralateral acoustic reflexes of the stapes fall out during stimulation of the affected side. Pathology of the brain stem at the level of the trapezoidal body leads to the loss of both contralateral reflexes. Volumetric processes that capture both cross paths and one of the non-cross paths are characterized by the absence of all reflexes except the ipsilateral on the healthy side. For the differential diagnosis of retrolabyrinth damage of the auditory tract, the decay of the acoustic reflex is of great importance.

Audiometry for auditory evoked potentials. Auditory evoked potentials of the brain are recorded in response to a series of short sound stimuli (clicks, tonal messages) that individually give a response of only a few microvolts and do not exceed the noise background of physiological processes in the brain. ? Regular responses (evoked potentials) are amplified by a computer by the summation method 100,000 times, and an irregular “interference” in the form of a background EEG is destroyed. Oae eae aey auaaeaiey neaiaea ec ooia eniieucoaony iee? Ii? Ioanni ?, then among doctors this method of hearing research was called computer audiometry.

For audiometry by evoked potentials, a device block is used (Fig. 1.2.15), which includes 2 electrodes, an EEG amplifier, a sound generator that generates short signals of 200 ms, a time sensor, a key, an adder (microprocessor with memory) and a recorder.

Fig. 1.2.15

Distinguish between cortical long-latent auditory evoked potentials (DSWP), stem short-latency auditory evoked potentials (VSWP) and mid-latent auditory evoked potentials (SSEP), presented in Fig. 1.2.16.

Fig. 1.2.16

DSWP reflect the function of the auditory centers of the temporal cortex. The study is conducted with a high degree of hearing loss, more often in children. It lasts more than an hour, in a shielded chamber, in a patient’s stationary state (in a dream after administration of chloral hydrate in an enema or other means).

VSWPs are associated with the stem function of the auditory system: I - with the auditory nerve; II - with a cochlear nucleus; III - with top olive; IV - с боковой петлёй, где происходит перекрест слуховых путей и V - с буграми четверохолмия. Отсюда делают вывод, на каком уровне поражена слуховая система. Исследование КСВП можно осуществлять в обычной обстановке без экранированной камеры, в состоянии бодрствования ребёнка или физиологического сна. К недостаткам исследования этого класса слуховых вызванных потенциалов относится невысокая частотная специфичность.

Источником ССВП некоторые авторы считают первичную слуховую кору, а другие расценивают это, как результат мышечных движений скальпа черепа и глаз. Исследование проводится у бодрствующих детей или в состоянии сна. ССВП обладают выраженной частотной специфичностью, что позволяет исследовать слуховые пороги в диапазоне от 500 до 4000 Гц с достаточной достоверностью.

Отоакустическая эмиссия (ОАЭ) представляет собой постоянную генерацию звуковых сигналов в рецепторе улитки. Это чрезвычайно слабые звуковые колебания, которые регистрируются в наружном слуховом проходе с помощью высокочувствительного низкошумящего микрофона. Колебания являются результатом активных механических процессов в наружных волосковых клетках,которые усиливаются за счёт положительной обратной связи, передаются базилярной мембране, индуцируя обратно бегущие волны, достигающие подножной пластинки стремени, приводящие в колебание слуховые косточки, барабанную перепонку и воздух в наружном слуховом проходе.

Различают спонтанную и вызванную ОАЭ. Спонтанная ОАЭ регистрируется в отсутствии звуковой стимуляции. Вызванная ОАЭ отмечается в ответ на звуковую стимуляцию. Реально при регистрации вызванной ОАЭ измеряются не движения барабанной перепонки, а звуковое давление после обтурации наружного слухового прохода. Для регистрации задержанной ОАЭ используют вводимый в наружный слуховой проход зонд, в корпусе которого размещены миниатюрные телефон и микрофон. Стимулами служат широкополосные акустические щелчки. Отводимый микрофоном ответный сигнал усиливается и напрвляется в компьютер через аналого-цифровой преобразователь.

У лиц с нормальным слухом пороги вызванной ОАЭ близки к субъективным порогам слышимости, а при патологии слуховой системы результаты исследования изменяются. ОАЭ может быть зарегистрирована у детей уже на 3-4 день после рождения, поэтому метод более популярен среди детей младшего и дошкольного возрастов при тугоухости и глухоте.
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Аудиометрическое обследование

  1. Подготовка к обследованию
    В соответствии с поставленной целью и задачами, контролирующие лица должны подготовиться к обследованию, изучив необходимые санитарные правила и нормы, гигиенические нормативы, методические рекомендации и др. При обследовании ПОП необходимо руководствоваться СП 2.3.6.1079-01 «Санитарно-эпидемиологические требования к организациям общественного питания, изготовлению и оборотоспособности в них
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    В каждом конкретном случае врач должен стремиться к тому, чтобы наименьшим числом исследований подтвердить правильность нозологического диагноза. План обследования больного, составленный лечащим врачом в соответствии с диагнозом заболевания, должен отличаться конкретностью, выбором наиболее информативных методов в нужной последовательности с минимумом инвазивности и с учетом переносимости
  3. Предоперационное обследование
    Как станет ясно из последующих глав, стандартной методики анестезии не существует. Вместе с тем перед операцией необходимо составить план анестезии (табл. 1-2), которая будет наилучшим образом соответствовать больному — его соматическому и психологическому состоянию, планируемой операции, заболеваниям, чувствительности к лекарственным средствам и опыту предыдущей анестезии. ТАБЛИЦА 1-2. Plan
  4. Survey methods.
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    With the onset of labor, the pregnant woman enters the admission department of the maternity hospital, where she is examined and a birth plan is drawn up. When examining a woman in childbirth, her medical history, physical examination, laboratory data, and assessment of the condition of the fetus are taken into account. Anamnesis for the course of this pregnancy, previous pregnancies, chronic diseases
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    Тактики лечения пациента при острой и хронической боли различаются. Если при острой боли можно приступать к лечению практически сразу, то при хронической боли часто бывают необходимы дополнительные исследования. Например, больные с послеоперационными болями нуждаются в гораздо меньшем объеме обследования, чем больные с 10-летними хроническими болями в пояснице, по поводу которых они многократно
  8. Examination of patients
    Examination of patients with extrasystolic arrhythmia should include methods that diagnose cardiac arrhythmias, determine the clinical and prognostic value of arrhythmia, select a treatment, and evaluate its effectiveness. Anamnesis. When interviewing a patient, they find out the following information: 1. Subjective manifestations of arrhythmia (palpitations, heart failure, tremors, or “fading”
  9. Patient Examination System
    The examination of the patient has its own system: a survey (history), examination, palpation, auscultation, laboratory and instrumental methods
  10. Sanitary and epidemiological examination of public catering establishments
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  12. Objective examination
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