Functional examination of the larynx

In clinical examination of laryngeal functions, changes in breathing and voice formation are considered first and foremost, as well as the use of a number of laboratory and functional methods. A number of special methods are used in phoniatrics - a section of laryngology that studies pathological conditions of the vocal function.

The examination of the voice function begins already during the conversation with the patient when assessing his voice and sound phenomena that arise when the respiratory function of the larynx is impaired. Aphonia or dysphonia, stridor or noisy breathing, distorted timbre of the voice and other phenomena may indicate the nature of the pathological process. Thus, with volumetric processes in the larynx, the voice is compressed, muffled, its characteristic individual timbre is lost, and the conversation is often interrupted by a slow, deep breath. On the contrary, in the "fresh" paralysis of the glottis constrictors, the voice seems to be exhaled almost soundlessly through the gaping glottis, the patient does not have enough air to pronounce a whole phrase, so his speech is interrupted by frequent breaths, the phrase is fragmented into separate words, hyperventilation of the lungs with respiratory pauses occurs during the conversation. In a chronic process, when compensation of the vocal function occurs due to other formations of the larynx, and in particular the vestibular folds, the voice becomes rough, low, with a tinge of hoarseness. In the presence of a polyp, fibroma or papilloma on the vocal fold, the voice becomes as if fragmented, trembling with admixtures of additional sounds arising as a result of the trembling of the formations located on the vocal fold. Laryngeal stenosis is recognized by the stridor sound that occurs during inhalation.

Special studies of the phonatory function become necessary only in cases when the subject of examination is a person whose larynx is the "working organ", and the "product" of this organ is the voice and speech. In this case, the objects of study are the dynamic indicators of external respiration (pneumography), phonatory excursions of the vocal folds ( laryngostroboscopy, electroglottagraphy, etc.). Using special methods, the kinematic parameters of the articulatory apparatus that forms speech sounds are studied. With the help of special sensors, the aerodynamic indicators of exhalation during singing and talking are studied. In addition, in special laboratories, spectrographic studies of the tonal structure of the voice of professional singers are carried out, the characteristics of the timbre coloring of their voices are determined, such phenomena as the flight of the voice, singing formants, voice noise immunity, etc. are studied.

Methods of visualization of the motor function of the larynx

As noted above, with the invention of the indirect laryngoscopy method, almost all the most common disorders of the larynx motor function were identified in a short period of time. However, as it turned out, this method could only identify the most severe disorders of vocal fold mobility, while the researcher missed those disorders that could not be recorded with the naked eye. Later, various devices began to be used to study the larynx motor function, first light-technical devices based on stroboscopy, then with the development of electronics - rheoglottography, electronic stroboscopy, etc. The disadvantage of laryngostrobosconia is the need to insert a recording optical system into the supraglottic space, which makes it impossible to record vocal fold vibrations during speech articulation, free singing, etc. Methods that record laryngeal vibration or changes in resistance to high-frequency electric current (rheoglottography) during phonation are free of these disadvantages.

Vibrometry is one of the most effective methods for studying the phonatory function of the larynx. Accelerometers are used for this, in particular, the so-called maximum accelerometer, which measures the moment when the measured section of the vibrating body reaches a given sound frequency or maximum acceleration in the range of phonated frequencies, i.e. vibration parameters. When registering larynx vibration, a piezoelectric sensor is used, generating an electric voltage with a frequency of its constriction equal to the frequency of oscillations of the vocal folds. The sensor is attached to the outer surface of the larynx and allows measuring accelerations from 1 cm/s2 ^to 30 km/s2 ^, i.e. within 0.001-3000 g (g is the acceleration of gravity of a body, equal to 9.81 m/s2 ⁾.

Laryngeal rheography

Rheography of the larynx was first performed by the French scientist Philippe Fabre in 1957. He called it glotography and it was widely used in the study of various functional disorders of the larynx in the 1960s and 1970s. This method is based on the same principle as REG and is designed to measure changes in resistance to metric current that occur in living tissues under the influence of biophysical processes occurring in them. If REG measures changes in resistance to electric current that occur when a pulse wave passes through brain tissue (changes in blood filling of the brain), then glotography measures the resistance to electric current of the vocal folds, which change their length and thickness during phonation. Therefore, during rheolaryngography, the change in resistance to electric current occurs synchronously with the phonatory vibration of the vocal folds, during which they come into contact with the frequency of the emitted sound, and their thickness and length change. The rheogram is recorded using a rheograph consisting of a power supply, a low-current generator (10-20 mA) of high frequency (16-300 kHz), an amplifier that amplifies the current passed through the larynx, a recording device, and electrodes placed on the larynx. The electrodes are placed so that the tissues being examined are between them, i.e. in the electric current field. In glottography, according to Fabre, two electrodes with a diameter of 10 mm, lubricated with electrode paste or covered with a thin felt pad soaked in isotonic sodium chloride solution, are fixed with an elastic bandage on the skin on both sides of the larynx in the area of the projection of the thyroid cartilage plates.

The shape of the rheolaryngogram reflects the state of the motor function of the vocal folds. During calm breathing, the rheogram has the form of a straight line, slightly undulating in time with the respiratory excursions of the vocal folds. During phonation, glottogram oscillations occur, close in shape to a sinusoid, the amplitude of which correlates with the loudness of the emitted sound, and the frequency is equal to the frequency of this sound. Normally, the parameters of the glottogram are highly regular (constant) and resemble oscillations of the microphone effect of the cochlea. Often, the glottogram is recorded together with the phonogram. Such a study is called phonoglotography.

In diseases of the laryngeal motor apparatus, manifested by non-closure of the vocal folds, their stiffness, paresis or mechanical impact on them of fibromas, papillomas and other formations, corresponding changes in the glottogram are recorded, to one degree or another correlating with the existing lesion. When analyzing the results of a glottographic study, it should be borne in mind that the parameters of the glottogram depend not only on the degree and time of closure of the vocal folds, but also on changes in their length and thickness.

Functional X-ray tomography

It is the method of choice in studying the motor function of the larynx. The essence of the method lies in layered frontal images of the larynx during pronunciation and singing of vowel sounds of different tones. The method allows studying the motor function of the vocal folds in the norm and in voice disorders associated with overfatigue of the vocal apparatus, as well as in various organic diseases of the larynx. The symmetry of the position of the right and left halves of the larynx, the uniformity of convergence or divergence of the vocal folds, the width of the glottis, etc. are taken into account. Thus, in the norm, during phonation of the sound "and", the greatest convergence of the vocal folds and symmetry of the excursion of radiopaque formations of the larynx are observed.

A type of functional radiography of the larynx is radiokymography, which involves frame-by-frame shooting of excursions of the mobile elements of the larynx with subsequent analysis of all criteria of these excursions. The advantage of this method is that it allows observation of the "work" of the vocal apparatus in dynamics and at the same time obtaining information about the larynx as a whole, visualization of its deep structures, the degree and symmetry of their participation in the phonatory and respiratory processes.