Noise-induced hearing loss: clinical guidelines

List of Abbreviations

ACTH – adrenocorticotropic hormone

INR – international normalized ratio

URT – upper respiratory tract

ME – medical expert commission

OAE – otoacoustic emission

WHO – World Health Organization

TTS – temporary threshold shift

Hz – hertz (unit of sound frequency)

"D" – dispensary observation (active clinical monitoring)

dB – decibel (unit of sound intensity)

DPOAE – distortion product otoacoustic emission

HLS – healthy lifestyle

EU – European Union

IRP – individual rehabilitation program

HrC – hearing loss risk criterion

ABR – auditory brainstem responses

ICD-10 – International Classification of Diseases, 10th Revision

OAE – otoacoustic emission

DPOAE – distortion product otoacoustic emission

PNS – paranasal sinuses

MPC – maximum permissible concentration / maximum permissible level

PME – periodic medical examination

HT – hearing threshold

PTS – permanent threshold shift

AEP – auditory evoked potentials

OHD – occupational hygiene data sheet

PPE – personal protective equipment

SNHL – sensorineural hearing loss

WRA – workplace risk assessment

CSNHL – chronic sensorineural hearing loss

OCC – occupational pathology center

ECG – electrocardiography

Terms and Definitions

Occupational noise –– the combination of various noises generated during the production process.

Maximum permissible noise level (MPL of noise) – the legally established upper limit of the noise factor level, the periodic or lifelong exposure to which does not cause diseases or health status changes detectable by modern methods either immediately or in the long term for the current and future generations.

Occupational sensorineural hearing loss – a bilateral chronic disease of the inner ear characterized by impaired sound perception, occurring exclusively or predominantly as a result of exposure to industrial noise exceeding the maximum permissible level.

Occupational risk - the probability of damage (loss) of health or death of an insured person associated with the performance of their duties under an employment contract (agreement) and in other cases established by Federal Law:

• risk of death resulting from acute or chronic action (given an established occupational connection — regardless of the duration of the illness);

• risk of an occupational disease as any abnormal state or impairment (other than injuries) caused by exposure to occupational factors and occurring over a period of more than one working day or shift.

Assessment of workers' occupational risks - assessment of the probability of harm to health resulting from exposure to harmful and hazardous occupational factors while performing duties under an employment contract.

Risk analysis - qualitative characteristics of exposure (tropism, vector property, synergism, antagonism, etc.); quantitative characteristics of exposure (level, time, length-of-service risk zones); prognosis of the probability of occupational disease, possible impact on offspring; risk categorization — assessment of the degree of risk and urgency of mitigation measures.

Pure-tone audiometry (audiometry) – a psychoacoustic method for examining hearing based on the patient's subjective perception of acoustic stimuli of various intensities.

Otoacoustic emission (OAE) – weak acoustic oscillations generated by the outer hair cells of the organ of Corti, which can be recorded using a special probe in the external auditory canal.

Auditory brainstem responses (ABR) – indicators reflecting the electrophysiological activity of the auditory pathway structures, recorded from the surface of the head in response to acoustic stimulation. The test results are displayed as a complex of positive peaks (I-VII), the most stable of which is wave V.

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Noise-induced hearing loss (occupational bilateral chronic sensorineural hearing loss) – a slowly developing, chronic, bilateral hearing impairment caused by exposure to industrial noise exceeding the maximum permissible level (80 dBA), representing damage to the sound-perceiving part of the auditory analyzer (neuroepithelial structures of the inner ear), manifested clinically as chronic bilateral sensorineural hearing loss [1, 2].

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

The main cause of noise-induced hearing loss [1, 2] is exposure to industrial noise exceeding sanitary and hygienic standards (MPLs). In the Russian Federation, the MPL for industrial premises noise is regulated in accordance with the requirements of SP 2.5.3650-20 "Sanitary and epidemiological requirements for individual types of transport and transport infrastructure facilities" and SanPiN 1.2.3685-21 "Hygienic standards and requirements for ensuring the safety and (or) harmlessness of living environment factors for humans" (effective from 03.01.2021).

Noise levels up to 90 dBA increase the proportion of TTS cases developing after a work shift under noise exposure conditions, which is an indicator of the risk of negative noise effects on the hearing organ, but does not indicate the onset of occupational pathology. With continued noise exposure, changes may progress over time up to the development of PTS [1, 2].

Increased labor intensity and severity, as well as a heating microclimate at the workplace, can increase the negative effect of noise and exacerbate the development of occupational hearing loss. Somatic diseases (of the cardiovascular, nervous, endocrine, and immune systems), which are negatively affected by long-term noise exposure extra-aurally, also aggravate noise-induced hearing loss [1-4].

There is no unified theory of the pathogenesis of this disease. The morphological substrate of noise-induced hearing loss (SNHL) consists of degenerative-dystrophic changes in the outer and inner hair cells (HCs) of the peripheral auditory analyzer (organ of Corti); the pathological process has an ascending character from the spiral ganglion and the auditory pathways to the auditory center in the temporal lobe of the brain [1, 2].

Noise acting on the auditory organ does not cause specific pathological changes for a long time, as the auditory analyzer possesses a high degree of adaptation to external influences. Immediately after the onset of sound stimulation, auditory sensitivity decreases and returns to baseline after the cessation of acoustic exposure. The main cause of cochlear neuroepithelial cell death under noise exposure is considered to be the damaging effect on intracellular structures of reactive oxygen species (ROS) released as a result of excessive mitochondrial activity and oxidative stress. The reaction of free radicals with plasma membranes leads to the formation of phospholipid and aldehyde peroxidation products and, ultimately, apoptosis of the hair cells. The apoptotic processes of outer hair cells (OHCs) are clinically manifested by a temporary (reversible) increase in tonal hearing thresholds, while necrotic cell changes manifest as PTS and the development of SNHL [3-5].

The nature of cochlear pathology is determined by the histogenetic features of the sensory neuroepithelial tissue, since the HCs of the organ of Corti are interphase highly differentiated cells whose population remains unchanged since intrauterine development. Therefore, from a general pathological standpoint, SNHL is a "hearing deficiency" based on a quantitative deficit of sensorineural elements at any level of the auditory analyzer [6].

Of great importance in the pathogenesis of noise-induced SNHL is the overstrain of inhibitory processes in the cortical and subcortical structures of the brain, the auditory zone of which is the first to react to noise exposure, triggering subsequent changes in other links of the auditory analyzer. At the same time, maladaptive changes in cerebral homeostasis develop, characterized by decreased functional activity of the cerebral cortex, disruption of interhemispheric and cortico-subcortical interactions, indicating dysfunction of cortical and stem structures [6].

The pathological changes caused by noise exposure are based on a "sensory conflict," which consists in the formation of a persistent pathological focus of excitation in the diencephalic region that alters the impulses from mechanoreceptors and interoceptors of sensory systems, blocking their input into the central nervous system. This leads to inadequate response reactions and a persistent, prolonged course of the pathological process. The effect of noise on the body is also viewed from the standpoint of chronic stress, which leads to a disruption of adaptive mechanisms and causes a number of complex neuro-reflex and neurohumoral shifts. At the same time, hearing loss is a severe emotional trauma leading to the development of neuroses and a decreased quality of life. Patients with hearing loss exhibit changes in their psychoemotional status, characterized by increased anxiety, emotional disorders, and reduced tolerance to stress, which indicates a disruption of adaptation mechanisms to external and occupational environments. Neurotic and depressive states, in turn, cause the development of psychosomatic diseases, forming a "vicious circle" of pathological reactions. Occupational noise affects not only the peripheral, but also the central sections of the auditory analyzer, causing persistent pathological foci of excitation in the cerebral cortex structures [7, 8].

Theoretical, experimental, and clinical data accumulated to date suggest that vascular disorders are the primary link in the pathogenesis of occupational sensorineural hearing loss (SNHL) [9-11]. Cerebrovascular disorders typically precede hearing loss and are detected in individuals in "noise-hazardous" occupations even with normal auditory function. Hearing impairment coincides with a decrease in pulse blood filling in the vertebrobasilar system, an increase in the tone of small and medium arteries, an increased frequency of angiospasms, and hindered venous outflow. Hemodynamic disorders are the leading pathogenetic link in the development of SNHL, driven by the anatomical features of the blood supply to the inner labyrinth and the high sensitivity of cochlear receptors to hypoxia due to their terminal position with the absence of *a. labyrinthi* collaterals, and a direct dependence on the state of central and cerebral hemodynamics [12]. Alterations in the ratio of the main types of central hemodynamics in workers of "noise-hazardous" industries lead to cardiovascular dysfunction. Changes in the elastic and mechanical properties of major arteries (particularly brachiocephalic) have been established: a decrease in pulse wave velocity and linear blood flow velocity, and an increase in total peripheral vascular resistance [10, 11, 13].

Currently, the concept of extra-aural effects of the nonspecific action of noise has been adopted—namely, the development of work-related diseases—along with compelling evidence regarding the impact of noise on the cardiovascular system and its indicator role in the formation of the body's protective and adaptive reactions. Noise is considered an additional risk factor for arterial hypertension, coronary artery disease, cardioneuropathy, and autonomic regulation disorders of heart rate. The impact of noise on the development of these disorders is manifold enhanced when combined with other predisposing factors (overweight, burdened heredity) [10, 13, 14].

Disorders of the autonomic, central nervous, and cardiovascular systems typically precede the development of specific (aural) changes in the auditory analyzer and manifest as asthenovegetative syndrome, hypothalamic syndrome, neurocirculatory dystonia, and discirculatory encephalopathy. At the same time, extra-aural manifestations may influence the development of SNHL due to the polyetiological nature of this disease [13, 14].

Noise exposure is accompanied by lipid metabolism disorders (decreased high-density lipoproteins (HDL) and apolipoprotein E in peripheral blood), which is considered one of the risk factors for occupational SNHL [3].

In recent years, data have emerged regarding the immunological component in the formation of sound perception disorders caused by noise exposure, associated with disruptions in the neuroendocrine and immune systems. Impairments in immunity and nonspecific resistance in workers of noise-and-vibration industries manifest as dysglobulinemia, decreased phagocytic activity, suppressed functional activity of neutrophils, and an imbalance in the cytokine profile with a predominance of proinflammatory cytokines [15].

An important role in the predisposition to many diseases belongs to tissue antigens of the human major histocompatibility complex (HLA system). Individuals suffering from occupational SNHL exhibit genetic defects in proteins (connexin-26, cadherin-23, cochlin, claudin-14, otoancorin, stereocilin, etc.) [16,].

In most modern industries, noise acts simultaneously with other occupational factors that exacerbate its effects: vibration, infrasound, neuro-emotional and physical strain, heating microclimate, and toxic substances [1, 2, 17].

Thus, the formation of pathology in the bodies of workers in "noise-hazardous" professions is caused both by the direct impact of excess acoustic energy on the auditory analyzer and by nonspecific functional disorders of the body's main systems.

1.3 Epidemiology of the Disease or Condition

In the Russian Federation, every third worker is exposed to elevated noise levels. Hearing loss worldwide, including noise-induced hearing loss, is a common occupational disease [18], and in our country, it accounts for one-third of all occupational diseases among workers of the Russian Federation [19]. High noise levels are traditionally recorded in the mining, petroleum refining, and petrochemical industries, metallurgy, construction, transportation, and other spheres of economic activity [1, 2, 19].

1.4 Features of Coding the Disease or Condition

Z57.0 – Occupational noise exposure (signs of noise effect on the auditory organ).

H83.3 – Noise-induced hearing loss.

These clinical guidelines do not address the diagnosis and treatment of acoustic trauma—a condition caused by the adverse effects of occupational noise, which is also coded as H83.3, but should be classified as a consequence of an industrial accident.

1.5 Classification of the disease or condition

The basis for classifying occupational SNHL is the quantitative criteria for noise-induced hearing loss. The classification is developed taking into account occupational health and workplace safety requirements, acceptable clinical practice of otorhinolaryngologist-audiologists, domestic approaches to medical and social evaluation (MSE), priorities for the early diagnosis of occupational noise-induced hearing loss, and the foundation for the timely implementation of hearing conservation programs (Table 1).

The "age-correction" procedure is not applied when evaluating the audiometric curve. This recommendation is due to the fact that in older patients with high-frequency hearing loss exceeding 45–50 dB, it is not possible to differentiate between the effects of noise and aging.

Table 1.

Classification of noise-induced hearing loss¹

Physiological involution of the auditory analyzer, which begins to develop in individuals aged over 35-37 years and is characterized by impaired sound perception at 8000-4000 Hz, reaches hearing loss fluctuation limits of up to 10 dB at speech frequencies by the age of 40-49 years. This indicator does not affect social hearing and has no significant clinical and social importance; at the same time, it eliminates discrepancies when formulating the conclusion on the presence of diagnoses of "Presbycusis" or "Signs of noise-induced effects on the auditory organ". The magnitude of presbycusis should be taken into account only before the development of the stage of prenosological hearing changes — Z57.0 "Signs of noise-induced effects on the auditory organ". When hearing thresholds exceed presbycusis parameters, the degree of hearing loss is assessed from the audiometric zero [1, 2, 20].

1.6 Clinical presentation of the disease or condition

Occupational sensorineural hearing loss (SNHL) — noise-induced hearing loss (NIHL) or occupational hearing loss — is a slowly progressive hearing impairment caused by exposure to occupational noise exceeding the permissible sanitary and hygienic level (MAC of 80 dBA) [1, 2], representing damage to the sound-perceiving part of the auditory analyzer (neuroepithelial structures of the inner ear), and manifesting clinically as chronic bilateral SNHL. Occupational hearing loss is always acquired, chronic, bilateral, and symmetrical SNHL. Depending on the level of lesion — cochlear (receptor, peripheral). According to ICD-10, we distinguish [1, 2].

Z57.0 — Occupational exposure to noise (signs of noise-induced effects on the auditory organ)

H83.3 — Noise effects of inner ear (noise-induced hearing loss) — "Bilateral chronic sensorineural hearing loss".

Occupational SNHL usually develops after a long period of work under conditions of intensive continuous or intermittent exposure to occupational noise exceeding the MAC. The disease develops slowly, over several years, usually 10-14 years, although the first prenosological changes on the audiogram may appear after 5 years of work in "noise-hazardous" working conditions [1, 2].

Initial complaints upon noise exposure are complaints regarding certain extra-aural effects of noise: sleep disturbance, increased irritability, headache; at later stages, complaints of impaired speech intelligibility (especially in a noisy environment), tinnitus, and hearing loss are added.

The otoscopic picture in the development of occupational SNHL is characterized by changes in the tympanic membrane in the form of retraction, turbidity, injection of blood vessels in the malleus handle area, and shortening of the light reflex. These changes are more frequently diagnosed under the combined action of noise and vibration, the latter altering the condition of the middle ear ossicular chain and the tension of the tympanic membrane. In the initial stages of the disease, the perception of whispered speech, both for the bass and descant groups of words, is not impaired [1, 2].

The earliest changes in sound perception upon noise exposure are effectively detected by DPOAE recording, which includes the absence of TEOAE recording in more than 4 frequency bands in individuals with normal tonal hearing thresholds, serving as an unfavorable prognostic sign of the negative impact of intensive occupational noise on the receptor apparatus of the inner ear and an indication for follow-up and timely rehabilitation measures. Therefore, TEOAE recording is preferable for hearing screening in individuals exposed to intensive occupational noise compared to transient-evoked OAE recording. Transient-evoked OAE parameters, along with DPOAE parameters, can serve as additional objective information to refine the contour of the tonal audiogram when resolving expert issues in individuals exposed to intensive occupational noise [1, 2].

The audiological picture of occupational SNHL is characterized by a typical audiometric pattern. Early changes in the auditory organ resulting from noise exposure initially manifest as an increase in the hearing threshold at frequencies of 12, 14, 16 kHz, and later at 4000 Hz, less frequently at 3000 Hz (a "notch") with a tendency to recover at 8000 Hz, which does not affect the perception of whispered and conversational speech and is recorded only using audiological methods [1, 2] (Fig. 1).

Fig. 1. High-frequency characteristic "notch" on the audiogram typical of noise-induced hearing loss.

Hearing thresholds for both air conduction and bone conduction in noise-induced SNHL are impaired to the same extent across the entire sound frequency range, i.e., there is an absence of air-bone gap in hearing thresholds.

The "notch" with continued noise exposure gradually spreads to adjacent frequencies, changing the shape of the audiometric curve. The exact location of the "notch" on the audiogram depends on the frequency characteristics of the occupational noise, as well as the length, diameter, and shape of the worker's external auditory canal. At this stage of sound perception impairment, there are no complaints of hearing loss. Subjective sensations of hearing deterioration increase as hearing loss progresses in the conversational frequency perception range. The severity of hearing impairment progressively increases with length of service, i.e., the duration of the noise factor action.

The audiometric picture of occupational SNHL is characterized by a gently sloping downward curve with the greatest increase in hearing threshold at 4000 Hz and a gradual increase in hearing thresholds at 2000, 1000, and 500 Hz. In noise-induced hearing loss, the arithmetic mean of hearing thresholds at conversational frequencies (500, 1000, and 2000 Hz) is always lower than at high frequencies (3000, 4000, and 6000 Hz), and the difference between the mean hearing threshold values at conversational and high frequencies is at least 15 dB. Hearing thresholds at 3000, 4000, and 6000 Hz are always higher than at 8000 Hz, unlike presbycusis, which exhibits a sloping downward curve. Noise exposure to the auditory organ generally does not lead to hearing loss of more than 75 dB at high frequencies and more than 40 dB at conversational frequencies. When noise-induced hearing loss develops in older workers (over 50-55 years of age), the prominence of the "notch" may be smaller. Therefore, in elderly people, the initial signs of noise-induced effects on the auditory organ are difficult to distinguish from age-related hearing loss (presbycusis) without analyzing their previous audiogram indicators. When SNHL is formed not only by noise exposure but also by age-related hearing loss or other causes, a "basin" rather than a characteristic "notch" is formed on the audiogram (Fig. 2).

Thus, the typical clinical and audiological signs of occupational SNHL are: a gradual, over several years (at least 5) increase in hearing thresholds of the sound perception impairment type; bilateral localization of the pathological process; absence of an air-bone gap in hearing thresholds; a downward-sloping audiological curve with the greatest increase in hearing thresholds (a "notch") at 4000 or 3000 Hz; a gradual progression of hearing threshold elevation at 1000 and 2000 or 3000 Hz; with a work experience of 20 years or more, a more significant increase in hearing thresholds at speech sound frequencies and the presence of pronounced "notches" at 2000 and 4000 Hz are possible [1, 2].

Fig. 2. Audiological picture typical of noise-induced hearing loss combined with presbycusis [6]

Occupational sensorineural hearing loss is characterized by changes in the most typical indicators of additional auditory function tests: a positive SISI (short increment sensitivity index) test with low differential limen for intensity values (DLT 0.6–0.4 dB) in early noise-induced hearing impairment; an increase in DLT up to 1.5–3 dB as the degree of sensorineural hearing loss progresses; an increased ability to discriminate intensity increments of the presented tone (Si-Si test scores) as the degree of sensorineural hearing loss progresses, which can reach 100% when the hearing threshold increases by 40 dB; a narrowing of the auditory field (convergence of the discomfort threshold with hearing thresholds) down to 90 dB; loudness recruitment within 2–30 dB compared to the loudness level sufficient for normal hearing; the presence of hyperacusis (unpleasant painful sensations in the ears and a sharp decrease in speech intelligibility when perceived sound is amplified); damage to the sensorineural part of the auditory analyzer (elevated hearing thresholds at frequencies of 16, 14, and 12 kHz during extended high-frequency audiometry); a type "A" tympanometric curve; preservation of the acoustic reflex, which is typically 60–70 dB, whereas the reflex is absent in high-degree hearing loss; a decrease in the amplitude of the TEOAE (transient evoked otoacoustic emissions) curve, loss of recording at individual sound frequencies (primarily at 4000 or 3000 Hz); and the absence of TEOAE recording when hearing thresholds increase by more than 30 dB. [1, 2, 20].

Fig. 3, 4, 5 demonstrate audiograms with varying degrees of hearing loss in occupational sensorineural hearing loss.

Fig. 3 Example of an audiogram in mild (I degree) occupational sensorineural hearing loss

Fig. 4. Example of an audiogram in moderate (II degree) occupational sensorineural hearing loss

Fig. 5. Example of an audiogram in severe (III degree) occupational sensorineural hearing loss

The clinical presentation of occupational sensorineural hearing loss includes signs of noise exposure affecting other organs and systems (extra-aural effects), which are functional in nature at early stages. Patients may complain of frequent headaches, irritability, increased fatigue, sleep disturbances, tinnitus, dizziness with dark spots before the eyes and flickering floaters, pain in the cardiac region, palpitations, etc. Neurological examination reveals increased or decreased tendon-periosteal reflexes, finger tremor, bright and persistent dermographism, acrocyanosis, hyperhidrosis, and sometimes mild instability in the Romberg position.

The combined effect of noise and vibration causes changes associated with vestibular analyzer irritation that exceeds the limits of physiological capabilities in terms of exposure duration and intensity. When analyzing electroencephalograms, the most significant parameters are the angular velocity of the slow phase of nystagmus, the duration of the latent period, the duration of nystagmus, its amplitude and frequency, and the ratio between the velocities of the slow and fast phases of nystagmus, which make it possible to judge the degree and level of vestibular function disorders. The most prominent disorders include the "ocular drift" sign and dissociation of vestibulo-ocular disorders between caloric and rotational tests, which are more frequently observed under the combined action of noise and whole-body vibration. A decrease in the excitability of the vestibular analyzer is characteristic of workers in "noisy" professions.

2. Diagnostics, medical indications and contraindications for diagnostic methods

Stage one is the establishment of a preliminary diagnosis, which is made either during periodic medical examinations or upon the worker's initial visit to any healthcare facility. Stage two is the final diagnosis, which may only be established by an occupational health facility holding a license for activities in the fields of "Occupational Pathology", "Expertise of the Association between Disease and Profession", and "Expertise of Occupational Fitness".

Criteria for establishing the diagnosis/condition: the diagnosis of occupational sensorineural hearing loss is established on the basis of pathognomonic findings:

1) patient complaints: gradual hearing loss (more pronounced at high sound frequencies), low-frequency tinnitus in both ears or in the head, and impaired speech intelligibility in a noisy environment;

anamnestic data: absence of a history of cardiovascular diseases (hypertension, coronary artery disease, etc.), cerebral atherosclerosis, cervical-thoracic spinal osteochondrosis, lipid metabolism disorders, systemic diseases (syphilis, diabetes mellitus), inflammatory and recurrent diseases of the middle ear and nasopharynx, prior infectious and viral diseases, head injuries, hearing loss in close relatives, or treatment with aminoglycoside antibiotics;

2) occupational history data and production noise intensity parameters: a work history of 10 years or more under industrial noise exposure, with noise levels exceeding sanitary and hygienic standards (80 dBA).

3) physical examination: palpation of the external ear and mastoid process is painless, percussion of the retroauricular region is painless, the external auditory canal is patent, the tympanic membrane is usually dull and somewhat retracted, the light reflex is shortened, and vascular injection is present along the handle of the malleus;

3) laboratory tests: peripheral blood parameters are within normal limits; lipid profile parameters are altered: total cholesterol, HDL, LDL, triglycerides, and atherogenic index are elevated;

4) instrumental examination: a clinical and audiometric profile with a sloping, descending pattern of bilateral, symmetrical sensorineural hearing impairment, with the greatest elevation of hearing thresholds (a "notch") at 4000 Hz, a gradual progressive increase in hearing thresholds at frequencies of 1000 and 2000 or 3000 Hz; absence of an air-bone gap, a positive SISI test with low differential limen for intensity values (DLT 0.6–0.4 dB) in early stages and a negative SISI test (DLT up to 1.5–3 dB) as the degree of sensorineural hearing loss progresses; increased Si-Si test scores; narrowing of the auditory field (convergence of the discomfort threshold with hearing thresholds) down to 90 dB; loudness recruitment within 2–30 dB compared to the loudness level sufficient for normal hearing; the presence of hyperacusis (unpleasant painful sensations in the ears and a sharp decrease in speech intelligibility when perceived sound is amplified); damage to the sensorineural part of the auditory analyzer (elevation of hearing thresholds at frequencies of 16, 14, and 12 kHz during extended high-frequency audiometry); a type "A" tympanometric curve; preservation of the acoustic reflex (up to 60–70 dB), whereas the reflex is absent in high-degree hearing loss; a decrease in the amplitude of the TEOAE curve, loss of recording at individual sound frequencies (primarily at 4000 or 3000 Hz); and the absence of TEOAE recording when hearing thresholds increase by more than 30 dB (the absence of TEOAE recording at 4000 Hz is an early sign of noise impact on the auditory organ) [1, 2].

2.1 Complaints and Anamnesis

Comments: (See Section 1.6 "Clinical Presentation"). The medical history must be taken in a targeted manner, specifying the presence of concomitant pathology that may affect the onset time and severity of the disease (hypertensive reactions, arterial hypertension, diabetes mellitus, lipid metabolism disorders, etc.). The physician must ask questions about the nature of the work, clarify the presence of noise in the workplace, and determine the duration of exposure. In all cases, it is necessary to thoroughly question the worker about previous occupations and the duration of exposure to harmful occupational factors that could have caused an undiagnosed hearing impairment in a timely manner.

Characteristic features of noise-induced hearing loss include:

- absence of recent acute diseases (including Covid-19),

- onset of irritability and sleep disturbances,

- onset of tinnitus in both ears or in the head preceding hearing loss,

- absence of a history of concomitant pathology that could affect the onset time and severity of the disease (chronic inflammatory middle ear diseases, hypertensive reactions, arterial hypertension, diabetes mellitus, lipid metabolism disorders, etc.),

- absence of a hobby for noisy activities in everyday life (loud music, shooting, etc.),

- absence of hearing loss in close relatives,

- gradual nature of hearing loss,

- employment in a profession classified as a "noise-hazardous" job category

- Work experience in noise exceeding the maximum permissible level (MPL) for more than 8–10 years.

Complaints and anamnesis make it possible to clarify the nature of hearing impairment and draw up an individualized differential diagnosis plan.

2.2 Physical Examination

Comments: an otorhinolaryngologist at the initial consultation, in the presence of typical complaints and a typical clinical and audiometric picture, and a patient work history in a "noise-hazardous" profession of 10 years or more, has the right to establish a preliminary diagnosis of an occupational disease of the hearing organ.

Examination of ENT organs is carried out for workers in "noisy" professions in the standard sequence (See Section 1.6 "Clinical Picture of the Disease").

Comments: see Section 1.6

Comments: performed to identify diseases of the nasal cavity and paranasal sinuses as additional potential causes of hearing function impairment.

Comments: follow-up consultation is provided to patients with a preliminary diagnosis of noise-induced hearing loss at an occupational health medical institution during an advanced examination when resolving the issue of the final diagnosis of an occupational hearing disorder.

Comments: daily examination is carried out as part of an additional, advanced patient examination at an occupational health medical institution on an outpatient basis or in a hospital when addressing the issue of the final diagnosis of an occupational hearing disorder, future fitness for work, determination of the "D" follow-up group, and development of an individual hearing rehabilitation program.

Comments: the initial consultation with an audiologist-otorhinolaryngologist is carried out in a healthcare facility (audiology room or audiology center) when an advanced examination of hearing function is necessary in cases of difficult or differential diagnosis of hearing organ diseases.

Comments: a follow-up consultation with an audiologist-otorhinolaryngologist is performed for a worker with a preliminary diagnosis of an occupational hearing disorder during an additional, advanced examination of hearing function to resolve the issue of the final diagnosis and determine a hearing rehabilitation program, including the possibility of hearing aid fitting.

Comments: performed as part of preliminary (upon employment) and periodic OMEs to identify internal organ pathology; determine contraindications based on the condition of internal organs for working in noise conditions; and prescribe treatment for comorbid conditions.

Comments: performed at an occupational health medical institution on an outpatient basis or under conditions of an additional, advanced inpatient examination to identify internal organ pathology; determine contraindications based on the condition of internal organs for working in noise conditions; and prescribe treatment for comorbid conditions.

Comments: carried out as part of preliminary (upon employment) and periodic OME to identify extra-auditory effects of noise on the nervous system; determine contraindications based on the condition of the worker's nervous system for working in noise conditions; and prescribe treatment for comorbid conditions.

Comments: performed at an occupational health medical institution on an outpatient basis or under conditions of an additional, advanced inpatient examination to identify extra-auditory effects of noise on the nervous system; determine contraindications based on the condition of the worker's nervous system for working in noise conditions; and prescribe treatment for comorbid conditions.

Comments: the examination is carried out within a healthcare facility based on OME results; in the presence of indications for establishing a preliminary diagnosis of occupational sensorineural hearing loss; to prepare a request to the territorial body of Rospotrebnadzor regarding the sanitary and hygienic characteristics of the working conditions at the patient's workplace, followed by the preparation of documents for referral to an occupational health medical institution in order to establish the final diagnosis of an occupational hearing disorder.

Comments: the examination is performed within an occupational health medical facility during outpatient or inpatient additional, in-depth evaluation regarding the establishment of a definitive diagnosis of occupational sensorineural hearing loss.

2.3 Laboratory Diagnostics

Introduction. The diagnostic test plan (scope and sequence) is drawn up by the attending physician and agreed upon with the patient based on the clinical presentation, complaints, and medical history in accordance with the presumptive diagnosis.

The patient examination methods used are intended to complement the clinical presentation in order to establish the nature and cause of hearing loss and determine management tactics. A carefully conducted examination makes it possible to differentiate noise-induced hearing loss from sensorineural hearing loss of vascular, toxic, or viral origin associated with chronic suppurative middle ear diseases, head injuries, otosclerosis, Meniere's disease, etc.

An individualized approach to a patient with hearing loss requires identifying comorbid conditions, taking into account the characteristics of their emotional profile, determining the presence of harmful occupational and environmental factors (occupational noise and additional occupational factors exacerbating its effects (vibration, psycho-emotional stress, forced working posture, unfavorable microclimatic conditions, etc.), inappropriate use of acoustic equipment, the possibility of domestic and occupational intoxications, use of ototoxic medications), as well as identifying and treating concomitant diseases pathogenetically associated with inner ear pathology (cardiovascular pathology: arterial hypertension, anemia, metabolic, allergic, and autonomic disorders, diseases of the endocrine and nervous systems, etc.).

Comments: performed as part of periodic medical examinations and during evaluation in an occupational health medical facility in accordance with the regulations of Orders of the Russian Ministry of Health No. 29n dated January 28, 2021; No. 911n dated December 21, 2012;

Comments: performed as part of periodic medical examinations and during evaluation in an occupational health medical facility in accordance with the regulations of Orders of the Russian Ministry of Health No. 29n dated January 28, 2021; No. 911n dated December 21, 2012

Comments: performed as part of periodic medical examinations and during evaluation in an occupational health medical facility in accordance with the regulations of Orders of the Russian Ministry of Health No. 29n dated January 28, 2021; No. 911n dated December 21, 2012

Comments: evaluation of lipid metabolism disorders includes the study of the following parameters: total cholesterol, HDL and LDL cholesterol, triglycerides, atherogenic index, which are of pathogenetic importance in the development of occupational sensorineural hearing loss and are performed as part of periodic medical examinations and during evaluation in an occupational health medical facility.

2.4 Instrumental Diagnostics

Comments: performed as part of periodic medical examinations and during evaluation in an occupational health medical facility

Comments: Weber and Rinne tuning fork tests are performed, necessary for the differential diagnosis of hearing impairment using C_{128 tuning forks.}

Comments: is also performed in all patients with sensorineural hearing impairment as part of periodic medical examinations and during evaluation in an occupational health medical facility; it is the primary method for the diagnosis and differential diagnosis of auditory organ diseases. (see section 1.6).

Comments: is also performed in all patients with sensorineural hearing impairment as part of periodic medical examinations and during evaluation in an occupational health medical facility; the method allows for the detection of early hearing changes not registered by other techniques. This primarily concerns damage to the sensorineural part of the auditory analyzer at ultra-high frequencies (12, 14, 16 kHz).

Comments: are performed on an outpatient basis or in an otorhinolaryngological or occupational health medical facility during in-depth, additional evaluation for the differential diagnosis of auditory organ diseases and determination of the topography of the pathological process.

Comments: is used as indicated to determine the perception of speech signals and assess auditory occupational fitness in accordance with industry regulations for occupational selection, primarily in civil aviation of the Russian Federation.

Comments: is prescribed for the differential diagnosis of auditory organ diseases and determination of the topography of the pathological process in the auditory analyzer; it is performed on an outpatient basis or in an occupational health medical facility during in-depth, additional evaluation

Comments: indicated for the diagnosis of early sensorineural hearing disorders caused by noise exposure and diagnosis verification; confirmation of the degree of hearing loss; exclusion of aggravation or malingering; as additional objective information to clarify the tonal audiogram profile when addressing expert review issues. Recording of various classes of DPOAE allows for the detection of early preclinical signs of inner ear damage, including those caused by intense occupational noise [1, 2, 22]. Changes primarily affect the 4 kHz frequency band. The absence of DPOAE recording in more than 4 frequency bands in individuals exposed to intense occupational noise is an indication for an expanded audiological examination. TEOAE recording is preferable for hearing screening in individuals exposed to intense occupational noise compared to DPOAE recording. DPOAE parameters, along with TEOAE parameters, can serve as additional objective information to clarify the tonal audiogram profile when resolving expert review issues in individuals exposed to intense occupational noise. Suppression of DPOAE parameters at the 4 kHz frequency, with normal tonal hearing thresholds, should be considered as an adverse prognostic sign of the negative impact of intense occupational noise on the receptor apparatus of the inner ear and serves as an indication for dynamic follow-up aimed at timely rehabilitation measures.

Comments: preferred for hearing screening in individuals exposed to intense occupational noise.

Comments: indicated for the diagnosis of early sensorineural hearing disorders caused by noise exposure; diagnosis verification; confirmation of the degree of hearing loss; exclusion of aggravation or malingering; as additional objective information to clarify the tonal audiogram profile when addressing expert review issues.

Comments: performed in specialized otorhinolaryngological institutions, audiology centers, and occupational health medical facilities. Indicated for workers in noise-hazardous occupations for the diagnosis of early sensorineural hearing disorders caused by noise exposure; diagnosis verification; confirmation of the degree of hearing loss; exclusion of aggravation or malingering.

Comments: Performed in specialized otorhinolaryngological institutions, audiology centers, and occupational health medical facilities. Indicated for noise-induced hearing loss as clinically indicated to objectify hearing thresholds; diagnose early sensorineural hearing disorders caused by noise exposure; verify the diagnosis; confirm the degree of hearing loss; exclude aggravation or malingering. However, it must be remembered that the fundamental method for objective diagnosis of hearing thresholds is the recording of auditory brainstem responses (ABR) [2, 20, 21].

Comments: indicated in the presence of complaints of dizziness, gait instability, etc., as part of periodic medical examinations and during comprehensive evaluation in an otorhinolaryngological or occupational health medical facility to detect vestibular function disorders. As part of periodic medical examinations for workers in noise-hazardous occupations, spontaneous nystagmus is assessed; if equipment is available, vestibulometry (A03.25.001) is performed to identify contraindications for working under noise exposure conditions.

Comments: prescribed for patients with noise-induced hearing loss to determine hemodynamic parameters of extracranial brachiocephalic arteries and identify potential restriction of blood supply to the stria vascularis of the inner ear [1, 2].

Comments: performed in patients with noise-induced hearing loss to identify potential causes of impaired blood circulation in the vertebrobasilar region and potential restriction of blood supply to the stria vascularis of the inner ear [1, 2].

Comments: performed in patients with noise-induced hearing loss to determine the condition of the paranasal sinuses and identify comorbid causes of impairment in the auditory analyzer [1, 2].

Comments: performed in patients with noise-induced hearing loss for differential diagnosis; used in various projections (head, temporal bones, cerebellopontine angles) with or without contrast agents and is prescribed in consultation with a radiation therapist depending on the clinical picture and preliminary diagnosis (in unilateral cochleovestibular disorders, a bilateral pathological process such as neurofibromatosis type II may be present) [1, 2].

Comments: MRI in various projections, including with contrast enhancement, is performed in patients with noise-induced hearing loss for differential diagnosis; clarification of the localization and extent of the pathological process (areas of the internal acoustic meatuses, cerebellopontine angles, posterior cranial fossa); for the purpose of differential diagnosis of diseases of the organ of hearing, and determining the topography of the pathological process [1, 2].

2.5 Other Procedures

Comments: performed to determine indications (contraindications) for treatment using reflexotherapy

Comments: performed to determine indications (contraindications) for physiotherapy treatment methods

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

Introduction. The goal of therapeutic measures in occupational noise-induced hearing loss (NIHL) is the timely elimination or effective arrest of the pathogenetic mechanisms of the disease and their consequences, as well as the normalization of the functional state of the auditory analyzer. Improving hearing through conservative treatments when exposed to occupational noise is possible only in the early stages of the disease and provided that the primary causal factor—noise—is eliminated.

Treatment for noise-induced hearing loss should be regular, individualized, comprehensive, and pathogenetic, including therapy prescribed in accordance with existing standards and treatment regimens that reflect modern concepts of the pathogenesis of disorders, depending on the leading symptoms, clinical course features, and the presence of comorbid pathology in the patient.

3.1 Conservative Treatment

Considering that the pathogenesis of noise-induced hearing loss is based on microcirculation disorders in the vascular stria of the inner ear, leading to irreversible degenerative changes in the inner ear neuroepithelium, therapeutic measures for noise-induced hearing loss are effective only in the earliest stages of hearing function impairment due to noise exposure, i.e., with diagnoses of "Signs of noise effects on the auditory organ - ICD-10 Z57.0" and "Noise-induced hearing loss - chronic bilateral sensorineural hearing loss grade I (mild)."

3.1.1 Pharmacological methods

In accordance with modern concepts of pathogenesis, the treatment of noise-induced hearing loss does not differ from non-occupational sensorineural hearing loss and should aim to normalize inner ear microcirculation, improve cerebral vascular hemodynamics, and enrich the blood with oxygen to reduce oxygen starvation in the neuroepithelium of the peripheral auditory analyzer (Organ of Corti). Courses of therapy for noise-induced hearing loss should last at least 10 days, be conducted regularly at least twice a year, and once a year for the high-risk group for occupational sensorineural hearing loss [1, 2, 22-24, 45].

Comments: prescribed for signs of noise exposure to the auditory organ (ICD-10 Z57.0) and grade I (mild) noise-induced hearing loss (in accordance with Decree of the Government of the Russian Federation No. 1180-r dated May 16, 2022 (ed. August 1, 2023) "On approval of the list of diseases or conditions (groups of diseases or conditions) for which the use of a medicinal product is permitted in accordance with the product characteristics not specified in the instructions for use" ICD-10 - H83.3) etc.) [26, 27, 28].

In grade II and III occupational hearing loss (chronic sensorineural hearing loss), drug therapy has low efficacy [1, 2, 22-24, 45].

- vitamins (ATC-A11) - B-complex vitamins (A11EA).

GRC CLOE 5Grade of Recommendation – C (Level of Evidence 5)

Comments: prescribed to workers in "noise-hazardous" professions complaining of tinnitus and diagnosed with: "Signs of noise effects on the auditory organ" (ICD-10 - Z57.0), "Chronic bilateral sensorineural hearing loss" (ICD-10 - H83.3) grade I (mild); the dosage regimen must comply with the drug instructions. [1, 2, 22-24, 45].

Comments: prescriptions are coordinated with specialized experts. Treatment of comorbid conditions must comply with medical care standards, be prescribed by specialist physicians depending on the form and severity of the identified pathology, and aim, among other things, to prevent the progression of the pathological process in the auditory analyzer.

3.1.2 Physical (non-drug) methods

Physical (non-drug) treatment methods: significantly increase the efficacy of drug therapy for occupational sensorineural hearing loss [1, 2, 22].

Comments: prescribed in the absence of contraindications. Contributes to the stabilization of autonomic regulation, enhancement of the sedative effect on the central nervous system, normalization of the activity of receptor structures in the inner ear (improving microcirculation and metabolism), reduction of subjective tinnitus, and improvement of the patient's overall well-being.

Comments: prescribed in the absence of contraindications. Contributes to the stabilization of autonomic regulation, enhancement of the sedative effect on the central nervous system, normalization of the activity of receptor structures in the inner ear (improving microcirculation and metabolism), reduction of subjective tinnitus, and improvement of the patient's overall well-being.

Comments: prescribed in the absence of contraindications. Contributes to the stabilization of autonomic regulation, enhancement of the sedative effect on the central nervous system, normalization of the activity of receptor structures in the inner ear (improving microcirculation and metabolism), reduction of subjective tinnitus, and improvement of the patient's overall well-being.

Comments: in the absence of contraindications, prescribed to patients with any severity of noise-induced hearing loss; complaining of tinnitus or head noise. Contributes to the stabilization of autonomic regulation, enhancement of the sedative effect on the central nervous system, normalization of the activity of receptor structures in the inner ear (improving microcirculation and metabolism), reduction of subjective tinnitus, and improvement of the patient's overall well-being.

Comments: magnetotherapy directed at the cervical spine and mastoid processes is prescribed to patients with clinically pronounced hearing loss due to noise (ICD-10: H83.3, grade I-II); presenting with complaints of tinnitus and head noise, in the absence of contraindications.  It is used to stabilize autonomic regulation, enhance the sedative effect on the central nervous system, normalize the activity of receptor structures in the inner ear (improving microcirculation and metabolism), reduce subjective tinnitus, and improve the patient's general well-being

Comments: in the absence of contraindications it is prescribed to patients with clinically pronounced forms of sound perception impairment, presenting with complaints of tinnitus and head noise. It helps stabilize autonomic regulation, enhances the sedative effect on the central nervous system, normalizes the activity of receptor structures in the inner ear (improving microcirculation and metabolism), reduces subjective tinnitus, and improves the patient's general well-being.

Comments: in the absence of contraindications it is prescribed to patients with various stages of sound perception impairment and degrees of noise-induced hearing loss, presenting with complaints of tinnitus and head noise. It helps stabilize autonomic regulation, enhances the sedative effect on the central nervous system, normalizes the activity of receptor structures in the inner ear (improving microcirculation and metabolism), reduces subjective tinnitus, and improves the patient's general well-being.

Comments: in the absence of contraindications it is prescribed to patients with various stages of sound perception impairment and degrees of noise-induced hearing loss, presenting with complaints of tinnitus and head noise. It helps stabilize autonomic regulation, enhances the sedative effect on the central nervous system, normalizes the activity of receptor structures in the inner ear (improving microcirculation and metabolism), reduces subjective tinnitus, and improves the patient's general well-being

Comments: in the absence of contraindications, it is prescribed to patients with various stages of sound perception impairment and degrees of noise-induced hearing loss; with complaints of tinnitus and head noise. It helps stabilize autonomic regulation, enhance the sedative effect on the central nervous system; normalize the activity of the receptor structures of the inner ear (improve microcirculation and metabolism), reduce subjective tinnitus; and improve the patient's general well-being

Comments: in the absence of contraindications, it is prescribed to patients with various stages of sound perception impairment and degrees of noise-induced hearing loss, with complaints of tinnitus and head noise. It helps stabilize autonomic regulation; enhance the sedative effect on the central nervous system, normalize the activity of the receptor structures of the inner ear (improve microcirculation and metabolism; reduce subjective tinnitus; improve the patient's general well-being; promote detoxification; increase the body's immune defenses; normalize the interaction between the oxidant and antioxidant systems; improve hemorheological properties; repair inner ear structures and reduce hypoxia in the stria vascularis of the spiral organ.

Comments: in the absence of contraindications, it is prescribed to patients with any degree of noise-induced hearing loss, with complaints of tinnitus and head noise. It helps stabilize autonomic regulation; enhance the sedative effect on the central nervous system, normalize the activity of the receptor structures of the inner ear (improve microcirculation and metabolism; reduce subjective tinnitus; improve the patient's general well-being; promote detoxification; increase the body's immune defenses; normalize the interaction between the oxidant and antioxidant systems; improve hemorheological properties; repair inner ear structures and reduce hypoxia in the stria vascularis of the spiral organ.

Comments: in the absence of contraindications, it is prescribed to patients with any degree of noise-induced hearing loss; with complaints of tinnitus and head noise. It helps stabilize autonomic regulation; enhance the sedative effect on the central nervous system, normalize the activity of the receptor structures of the inner ear (improve microcirculation and metabolism; reduce subjective tinnitus; improve the patient's general well-being; promote detoxification; increase the body's immune defenses; normalize the interaction between the oxidant and antioxidant systems; improve hemorheological properties; repair inner ear structures and reduce hypoxia in the stria vascularis of the spiral organ.

Comments: recommended for all patients with impaired auditory function; massage (classical, vacuum, hydrojet, and other types) has a beneficial effect on the body as a whole and the hearing organ in particular. General massage reduces psycho-emotional tension and the severity of psycho-emotional disorders; improves trophic processes; activates metabolism; improves blood flow and lymph circulation; reduces muscle spasm and improves muscle tone and elasticity.

Comments: medical neck massage is recommended for all patients with impaired auditory function, helps normalize blood circulation in the cervical zone; eliminates hypoxia phenomena in the inner ear; improves oxygenation and restores the function of the neuroepithelium of the spiral organ.

Comments: collar zone massage is recommended for all patients with impaired sound perception, helps normalize blood circulation in the vertebrobasilar basin; eliminates hypoxia phenomena in the inner ear; improves oxygenation and restores the function of the neuroepithelium of the spiral organ.

Comments: prescribed to all patients with initial signs of sound perception impairment to enhance the effect of baseline therapy; improves blood flow in the vertebrobasilar region; restores metabolism in inner ear cells; delivers oxygen and biologically active substances necessary for the normal functioning of the hair cells of the spiral organ.

Comments: recommended for all patients with initial manifestations of auditory function impairment; the medicinal substance, deposited in close proximity to the inner ear structures, improves cellular and tissue metabolism, tones and improves the conduction of nerve impulses in the receptor apparatus of the inner ear.

Comments: binaural or monaural digital hearing aid fitting is performed in combination with the therapeutic and rehabilitation measures listed above.

3.2 Surgical Treatment

Comments: in noise-induced hearing loss, surgical treatment is not indicated [1, 2].

3.3 Other Treatment

Comments: helps reduce the negative effects of noise exposure on the body, normalize the emotional sphere, correct stress, and relieve fatigue, the development of which is inevitable when working in noisy industrial environments.

Comments: the significance of lipid metabolism disorders in the pathogenesis of sensorineural hearing loss is taken into account; dietary nutrition is prescribed individually, depending on indications; if no indications are found for other therapeutic diets, diet table No. 10 or 15 is used.

4. Medical Rehabilitation and Sanatorium-Resort Treatment

Introduction. Medical rehabilitation and sanatorium-resort treatment play a major role in the system of measures to reduce occupational and production risks of noise-induced hearing loss. From the standpoint of preventive medicine, all workers in "hazardous" professions should be regarded as workers of occupational risk categories, based on the degree of influence of which individuals should be selected for rehabilitation or sanatorium-resort treatment. For "apparently healthy" individuals exposed to occupational noise, sanatorium-resort rehabilitation (treatment) is considered as the prevention of risk factors for occupational and work-related (somatic) diseases, which can be carried out not only in sanatoriums, but also in recreation facilities (boarding houses, recreation centers), and sanatorium-preventoria. The frequency of sanatorium-resort rehabilitation for "apparently healthy" workers exposed to occupational noise should be justified by the intensity level and nature of the noise factor, as well as the average timeframes for the development of negative effects of noise exposure on the body [2, 29].

The principles of rehabilitation and recreation for individuals working under industrial noise exposure conditions are based on taking into account the negative impact of working conditions on workers' bodies, necessary primary and secondary prevention measures, and the possibilities of restorative treatment and health improvement. Specific decisions on protective, preventive, health-improving, and therapeutic measures are based on: hygienic assessment indicators of workplace working conditions; i.e., assessment of probable causes that led to the disease depending on the level, duration, and dose of noise exposure, gender, age, and length of service (occupational risk indicators); results of direct medical observations and examinations [2, 29, 30].

Comments: attention is paid to discussions on the causes and methods of preventing diseases caused by noise exposure; the importance of using hearing protection equipment (HPE); and adherence to a healthy lifestyle.

Comments: treatment is carried out during the vacation period, including wellness activities and non-pharmacological therapy to normalize the emotional sphere, correct stress, and relieve fatigue. Indications and the scope of therapeutic and wellness measures must be determined by the results of comprehensive examinations by a general practitioner (physician), neurologist, surgeon, medical psychologist (psychiatrist), ophthalmologist, otorhinolaryngologist, and, if necessary, other specialists. Treatment is prescribed taking into account strict adherence to the therapeutic and wellness regimen; combating risk factors for somatic diseases that can worsen hearing function (arterial hypertension, dyslipidemia, aortic atherosclerosis, cerebral vessel atherosclerosis, cervical osteochondrosis, etc.). The measures are implemented during the worker's stay in a sanatorium or in a day hospital setting (during vacation) at least once a year; sanatorium-resort rehabilitation can be carried out not only in sanatoriums, but also in recreation facilities (boarding houses, holiday camps), and sanatorium-profilactoriums. The frequency of sanatorium-resort rehabilitation for "practically healthy" workers exposed to occupational noise is justified by the intensity level and nature of the noise factor, as well as the average timeframes for the development of negative effects of noise on the worker's body, including the hearing organ.

Comments: programs and standards should be compiled depending on: the nature, level of action, and exposure of occupational noise and associated other risk factors; the class of working conditions by the degree of hazard and harmfulness (i.e., the level of occupational and professional risk); the worker's health level; the characteristics of clinical forms and the severity of hearing impairment.

Comments: the results of rehabilitation should be considered: elimination of hearing loss manifestations or significant improvement in hearing acuity, positive dynamics according to instrumental examination data (audiometry), and improvement in the general well-being and psycho-emotional state of the worker's body.

Comments: therapeutic massage (classical, acupressure, vacuum) is performed: medical neck massage, collar zone massage, daily, up to 10 procedures per course.

Comments: auditory training is recommended as an adjunctive treatment method in individuals with mild chronic sensorineural hearing loss and in individuals with hidden hearing loss. Auditory training is conducted on the basis of virtual reality using various audiovisual scenarios in a virtual reality headset. Sessions are held daily, one procedure per day for 7 days, with the duration of each session being 15 minutes with a single 2-minute break.

Comments: a course of metered physical loads is recommended for training balance and equilibrium, including the use of virtual reality, daily or every other day, for 30 minutes, with a course of 20 procedures.

5. Prevention and Dispensary Observation

Introduction. The modern concept of personalized medicine is based on the principles of preventive medicine, including the principles of systems medicine - the "4P" model: ("predictiveness" – prediction of a disease before its symptomatic manifestation; "personalization" – taking into account the individual characteristics of the patient; "preventiveness" – prevention of the disease; "participatory" – patient participation, implying the active involvement of the patient in identifying their individual characteristics and implementing preventive measures) [31, 32].

Depending on the state of health, the presence of disease risk factors, or pronounced pathology, the WHO distinguishes 3 types of disease prevention: primary, secondary, and tertiary. Noise-induced hearing loss can be prevented through primary and secondary prevention, the implementation of which is extremely important due to the lack of effective treatments for occupational sensorineural hearing loss [32].

5.1 Primary prevention

Introduction. The main areas of primary prevention are: environmental and socio-hygienic monitoring of the environment and working conditions; formation of a healthy lifestyle, sanitary and hygienic education, including the reduction of tobacco and alcohol consumption, prevention of drug addiction, and involvement of workers in "noise-hazardous" professions in physical culture; medical examinations of workers in order to reduce the impact of harmful occupational risk factors, including noise; early detection and prevention of the development of occupational diseases of the hearing organ. Measures for the primary prevention of hearing disorders in workers of "noise-hazardous" professions must include three main areas – technical, organizational, and medical measures [29, 31, 32].

Comments: Measures to comply with occupational health and safety standards to reduce occupational risks include the monitoring of working conditions, which is carried out on the basis of the special assessment of working conditions (SAWC) to establish classes (subclasses) of working conditions at workstations, identify areas, workstations, and equipment with industrial noise levels exceeding established sanitary and hygienic parameters; an assessment of the degree of room sound insulation, the degree of noise and vibration hazard of equipment and technological processes is carried out; measures are determined and developed to improve working conditions, reduce industrial noise levels and factors potentiating its harmful effects (vibration, psycho-emotional stress, forced working posture) to established sanitary and hygienic standards; the introduction of rational work activity regimens and health promotion of the workforce.

Technical measures include changing production technologies with the replacement or exclusion of processes accompanied by the induction of high industrial noise levels; the development and implementation of collective and individual noise protection measures; information on the risk of hearing impairment; information on the need to use hearing protection devices; training in special occupational safety schools for workers in "noise-hazardous" professions.

Collective noise protection measures include noise-absorbing panels, partitions, ceilings, etc. Personal hearing protection devices against noise include anti-noise helmets, earplugs, and ear inserts («earplugs»), which should be used in cases where the permissible noise levels are exceeded, as well as when technical means and methods of noise reduction cannot be applied, or when they fail to ensure noise reduction to standard parameters.

Comments: the method allows to estimate the probability of noise-induced hearing loss, determines the attributable or excess risk of hearing loss, which is numerically equal to the difference in absolute risks in homogeneous population groups of individuals exposed and unexposed to noise.

Comments: the list of hearing protection devices includes anti-noise earplugs, anti-noise ear inserts, anti-noise helmets, and suits. Hearing protection devices should be used only if it is impossible to limit hazards/risks by means of collective protection and other preventive measures. At the same time, the employer must provide PPE free of charge to employees and take measures to ensure their proper use and mandatory maintenance.

Comments: the regimens consist in reducing the time spent under noise and vibration exposure and alternating with short rest breaks outside the noise—intra-shift work and rest regimens. The development of intra-shift work and rest regimens is based on determining the severity of the work performed, the total amount of time for rest, the optimal duration of individual rest intervals, and establishing their rational distribution throughout the entire work shift.

For operator work during the work shift, depending on the production load, 10-minute regulated breaks should be provided, backed by worker replacement. With a high production load - every 2 hours of work; with an average level of production load - at least every four hours of work. For this purpose, specially developed work regimens are used, which provide for regulated breaks (limiting the time of work with vibration or noise to no more than 2/3 of the work shift; introduction of technological processes providing for micro-pauses during the performance of "noise-hazardous" operations; work in a multidisciplinary team with a periodic change of a "noise-hazardous" profession to a "noise-safe" profession, etc.).

Comments: these measures are of auxiliary importance, serving as a complement to the complex of sanitary, technical, and hygienic measures for the health protection of workers in "noise-hazardous" professions. They significantly improve the adaptation process to the industrial environment, increase labor productivity, and enhance the immunobiological and protective properties of the body. Such measures include: occupational gymnastics, ultraviolet irradiation, inhalations, vitaminization, balanced nutrition, provision of vitamins, adaptogens, etc.

Comments: periodic medical examinations are carried out in compliance with all necessary medical regulations defined by the requirements of the current legislation of the Russian Federation and the Order of the Russian Ministry of Health dated January 28, 2021, No. 29n

5.2 Secondary prevention

Introduction. The priority measures of secondary prevention are: targeted sanitary and hygienic education of the population, including working population; follow-up (dispensary) medical examinations to assess health status, including for targeted population groups, determination of measures and programs for health improvement, rehabilitation, and treatment; courses of preventive treatment and targeted health improvement; medical and psychological adaptation to changes in the health status situation; reduction of the influence of environmental and occupational risk factors, preservation of residual working capacity, as well as the possibility of adaptation in the professional and social environment to create conditions for optimal life support and improved quality of life.

Comments: dispensary observation of workers exposed to industrial noise above established sanitary and hygienic parameters is a set of measures, including mandatory preliminary (upon employment) and periodic medical examinations carried out in accordance with federal and industry regulations.

Comments: follow-up groups are formed based on the results of periodic medical examinations.

Comments: group I "A" should include practically healthy workers exposed to industrial noise not exceeding 90 dBA, regardless of work experience, as well as practically healthy workers exposed to industrial noise exceeding 90 dBA with a work experience of up to 10 years, and they are subject to a dispensary examination (periodic medical examination) once a year. Dynamic follow-up includes identifying risk factors, comprehensive primary prevention and treatment of existing chronic somatic diseases, counseling on occupational health, safety and hygiene, ergonomics, selection, correct use, storage, and sanitary processing of hearing protection devices.

Comments: group I "B" should include apparently healthy individuals working under conditions of noise exposure exceeding 90 dBA with a work experience of over 10 years. Preventive measures are the same as for group I "A", supplemented by recommendations for collar-zone massage (A21.01.003.001) 2 times a year, and reflexology for ear diseases (A21.25.001) 1 time a year.

Comments: group II should include workers in whom clinical and audiological examination during PME reveals "Signs of noise effects on the auditory organ" (ICD-10 Z57.0). Preventive measures are the same as for group I "B", supplemented by recommendations for hyperbaric oxygenation for diseases of the auditory organ (A20.25.001) and prescription of medications for diseases of the auditory organ (A25.25.001); sanatorium-resort rehabilitation 1 time a year.

Comments: group III "A" should include workers with an established diagnosis of noise-induced hearing loss (ICD-10 H83.3) – "Chronic bilateral sensorineural hearing loss, degree I "A" hearing impairment." Workers are able to work in their profession; referral to an occupational pathology medical institution 1 time a year is indicated; development of a hearing IRP. Preventive measures are the same as for group II, supplemented by recommendations for expanded prescription of medications for diseases of the auditory organ (A25.25.001), application of complex non-drug treatment (See section 3.2), and sanatorium-resort treatment 1 time a year.

Comments: group III "B" should include workers with an established diagnosis of noise-induced hearing loss (ICD-10 H83.3) – "Chronic bilateral sensorineural/ sensorineural hearing loss of the first I "B" degree" combined with hypertension stage 2 or higher, chronic cerebral ischemia stage 2 or higher. Preventive measures are the same as for group III "A", supplemented by the treatment of combined vascular pathology. The course of treatment is 2 times a year. Workers are fit for their profession provided they undergo dynamic follow-up at an occupational pathology medical institution 2 times a year, and they must be informed about the increased health risk if they continue working in noise conditions. A hearing IRP must be developed for the employee.

Comments: group III "C" should include workers with an established diagnosis of hearing loss (ICD-10 H83.3; H90.3) – "Chronic bilateral sensorineural hearing loss" of the second or higher degree of hearing impairment of any etiology. The worker is recognized as unfit to continue working under conditions of occupational noise exposure and is referred to the ITU to determine the degree of disability and material compensation for health loss due to an occupational disease; development and implementation of a hearing IRP. Preventive measures are the same as for group III "B", carried out at the place of territorial affiliation to a healthcare institution 2 times a year.

Comments: the development of a hearing IRP and monitoring of its implementation are carried out by an otorhinolaryngologist or an audiologist-otorhinolaryngologist.

6. Organization of Medical Care

Introduction. The procedure for organizing medical care for occupational diseases, including noise-induced hearing loss, is determined by the Decree of the Government of the Russian Federation "On Approval of the Regulation on Investigation and Registration of Occupational Diseases" dated December 15, 2000, No. 967 and the Decree of the Government of the RF dated July 5, 2022, No. 1206 "On the procedure for investigating and recording cases of occupational diseases of workers (effective from March 1, 2023) and orders of the Ministry of Health of the RF: dated May 28, 2001, No. 176 "On improving the system of investigation and registration of occupational diseases in the Russian Federation"; dated November 13, 2012, No. 911n "On approval of the procedure for providing medical care for acute and chronic occupational diseases."

The diagnosis of an occupational disease is established in two stages: establishing a preliminary and a final occupational disease.

6.1 Medical care delivery procedure

- A preliminary diagnosis of occupational sensorineural hearing loss (SNHL) can be established by an otorhinolaryngologist or an audiologist-otorhinolaryngologist of any medical organization (healthcare institution) at the place of contact in an outpatient setting.

- A physician of the medical organization (healthcare institution), upon establishing a preliminary diagnosis of occupational SNHL, refers the patient within 24 hours to an occupational pathologist of the medical organization (at the place of residence or stay) to confirm (or not confirm) the preliminary diagnosis of occupational SNHL.

- The occupational pathologist of the medical organization establishes (confirms/does not confirm) the preliminary diagnosis of occupational SNHL and, upon confirmation, sends a notification of the preliminary diagnosis of occupational SNHL to the Rospotrebnadzor center within a 3-day period.

- Rospotrebnadzor specialists draw up a sanitary and hygienic characteristic (SHC) of the worker's working conditions within a 2-week period and send it to the occupational pathologist of the medical organization.

- The occupational pathologist of the medical organization analyzes the SHC and, within a month, refers the patient with the preliminary diagnosis of occupational SNHL to an occupational pathology medical institution to resolve the issue of establishing the final diagnosis of occupational SNHL.

- When referring a patient to an occupational pathology medical organization, the following must be provided: a copy of the work record book from the place of work, an extract from the results of the pre-employment and periodic PMEs, examination results from other medical organizations, copies of audiograms for the entire period of work under noise exposure conditions, and the SHC. All documents must be certified by the seals of the institutions.

- An occupational pathology medical organization holding a license to provide medical care in the specialties: "Occupational Pathology", "Expertise of the Link Between Disease and Profession", "Expertise of Professional Fitness", at a medical commission meeting, taking into account all the information provided, establishes (or does not establish) the final diagnosis of occupational SNHL.

- The decision on the final diagnosis of occupational SNHL can be made on an outpatient basis based on clinical health data and all submitted documents, or after an inpatient examination at an occupational pathology medical institution, taking into account the results of an additional, in-depth health examination, including that of the auditory organ.

- The occupational pathology medical organization, after establishing the final diagnosis of occupational SNHL, sends a notification of the final diagnosis of occupational SNHL to 4 addresses within a 3-day period: the Rospotrebnadzor center, the employer, the insurer, and the medical organization that referred the patient.

6.2 Indications for hospital admission

Indications for hospitalization in a medical organization when establishing a preliminary diagnosis of occupational SNHL are absent.

The indication for hospitalization in an occupational pathology medical organization is the need for an additional, in-depth examination of the patient's health status and auditory system in order to establish a definitive diagnosis of occupational sensorineural hearing loss.

6.3 Criteria for discharge from a medical organization

The grounds for discharging a patient from an occupational pathology medical organization are the resolution of the issue regarding the establishment or exclusion of a definitive diagnosis of occupational sensorineural hearing loss.

7. Additional Information

Extraaural pathology (cardiovascular diseases, lipid metabolism disorders, etc.) potentiates the effect of noise on the auditory organ and increases the risk of hearing loss. Against the background of vascular pathology, occupational sensorineural hearing loss is characterized by a shorter development time, an additional increase in high-frequency hearing thresholds, and the gradual disappearance of audiological signs specific to noise-induced damage. Noise can cause the development of somatized depressive disorder [2].

The negative effect of noise on the body is significantly increased by noisy everyday activities (hobbies involving shooting, hunting, loud music, especially through headphones), alcohol abuse, tobacco smoking, and drug use. An unfavorable background for the impact of industrial noise on a worker includes a history of treatment with aminoglycoside antibiotics, deafness in close relatives, and a history of head trauma [1, 2, 31].

Criteria for Evaluating the Quality of Medical Care

References

Appendix A1. Working Group Composition

Daikhes Nikolay Arkadyevich ^{1, 2} – Corresponding Member of the RAS, DSc (Medicine), Professor, Vice-President of the National Medical Association of Otorhinolaryngologists, Chairman of the Healthcare Commission of the Civic Chamber of the Russian Federation, Chief freelance Otorhinolaryngologist of the Russian Ministry of Health, Honored Scientist of the Russian Federation, Honored Healthcare Worker of the Russian Federation. No conflict of interest.

Bukhtiyarov Igor Valentinovich ^{3, 4} – Academician of the RAS, DSc (Medicine), Professor, President of the Association of Physicians and Specialists in Occupational Health, Member of the International Commission on Occupational Health (ICOH), Chief freelance Occupational Health Physician of the Russian Ministry of Health, Honored Scientist of the Russian Federation. No conflict of interest.

Pankova Vera Borisovna ^{1, 5, 6} – DSc (Medicine), Professor, Member of the Russian MTA, Member of the Presidium of the National Medical Association of Audiologists, Member of the National Medical Association of Otorhinolaryngologists, Member of the Association of Physicians and Specialists in Occupational Health. No conflict of interest.

Bushmanov Andrey Yuryevich ⁷ – DSc (Medicine), Professor, Member of the Association of Physicians and Specialists in Occupational Health, Chief freelance Occupational Health Physician of the FMBA of Russia. No conflict of interest.

Fedina Irina Nikolaevna ^{1, 3} – DSc (Medicine), Professor, Member of the Association of Physicians and Specialists in Occupational Health, Member of the National Medical Association of Otorhinolaryngologists, Member of the International Commission on Occupational Health (ICOH). No conflict of interest.

Serebryakov Pavel Valentinovich ^{1, 3, 5} - DSc (Medicine), Professor, Member of the Association of Physicians and Specialists in Occupational Health. No conflict of interest.

Machalov Anton Sergeevich ^{1, 2, 5} – DSc (Medicine), Associate Professor, Member of the National Medical Association of Otorhinolaryngologists. No conflict of interest.

Tavartkiladze George Abelovich ⁵ - DSc (Medicine), Professor, Member of the Russian MTA, Academician of the National Academy of Sciences of Georgia, President of the National Medical Association of Audiologists, Member of the National Medical Association of Otorhinolaryngologists, President of the International Academy of Otorhinolaryngology – Head and Neck Surgery, Secretary-General of the International Society of Audiology. No conflict of interest.

Shigan Evgeny Evgenyevich ^{2, 3} – PhD (Medicine), Executive Director of the Association of Physicians and Specialists in Occupational Health, National Secretary of the International Commission on Occupational Health (ICOH) in the Russian Federation. No conflict of interest.

Nikitin Mikhail Vladimirovich ⁹ – DSc (Medicine), Chief freelance specialist in sanatorium-resort treatment of the Ministry of Health of the Russian Federation. No conflict of interest.

Bomshtein Nataliya Gennadievna ¹ - Member of the National Medical Association of Otorhinolaryngologists. No conflict of interest.

Evgenia R. Tsygankova ⁵ - PhD in Medicine, Associate Professor, Member of the National Medical Association of Audiologists, Member of the National Medical Association of Otorhinolaryngologists. There is no conflict of interest.

Volokhov Leonid Leonidovich ¹ - Member of the National Medical Association of Otorhinolaryngologists. No conflict of interest.

Skryabina Larisa Yuryevna ⁸ - PhD (Medicine), Member of the National Medical Association of Otorhinolaryngologists. No conflict of interest.

Kuryerov Nikolay Nikolaevich ³ - PhD (Biology), Member of the Association of Physicians and Specialists in Occupational Health. No conflict of interest.

Prokopenko Lyudmila Viktorovna ³ - DSc (Medicine), Professor, Member of the Association of Physicians and Specialists in Occupational Health. No conflict of interest.

Developing institutions:

1. National Medical Research Center for Otorhinolaryngology of the FMBA of Russia.

2. Pirogov Russian National Research Medical University of the Russian Ministry of Health.

3. Izmerov Research Institute of Occupational Health.

4. I.M. Sechenov First Moscow State Medical University of the Russian Ministry of Health (Sechenov University).

5. Russian Medical Academy of Continuous Professional Education of the Russian Ministry of Health.

6. State Scientific Center - Burnasyan Federal Medical Biophysical Center of FMBA of Russia.

7. All-Russian Research Institute of Railway Hygiene of Rospotrebnadzor.

8. Sverжевsky Research Clinical Institute of Otorhinolaryngology of the Moscow Healthcare Department.

9. National Medical Research Center for Rehabilitation and Balneology of the Russian Ministry of Health.

Appendix A2. Methodology for Developing Clinical Guidelines

In modern international practice, it is standard to align approaches to the diagnosis, treatment, and rehabilitation of diseases with the ICD-10 classification to ensure the highest possible quality of care. The basis is formed by Order No. 103n of the Russian Ministry of Health dated February 28, 2019, «On Approval of the Procedure and Timelines for the Development and Revision of Clinical Guidelines, Their Standard Form, and Requirements for Their Structure, Content, and Scientific Validity of Information Included Therein» (as amended), and the Clinical Guidelines «Noise-Induced Hearing Loss», reviewed and approved at the meeting of the National Medical Association of Otorhinolaryngologists and the Association for Occupational Medicine, and included in the Rubricator of Clinical Guidelines of the Russian Ministry of Health, 2018 (ID: KR609). As modern approaches to the diagnosis, treatment, and rehabilitation of noise-induced hearing loss develop and are implemented, the clinical guidelines are updated. New information emerges at scientific and practical conferences, national and international symposia, which members of the working group monitor and analyze as it becomes available. Given the need for an interdisciplinary approach, specialists in other fields may be included in the working group.

Target audience for these clinical guidelines:

1. otorhinolaryngologist

2. aviation and space medicine specialist

3. diving medicine specialist

4. occupational health physician

5. medical and social appraisal specialist

6. medical prevention physician

7. medical rehabilitation physician

8. general hygiene physician

9. sanitary and hygienic laboratory testing specialist

10. occupational pathologist

11. otologist-audiologist / otorhinolaryngologist-audiologist

12. hearing aid specialist / audiologist-prosthetist

13. forensic medical expert

14. medical prevention physician;

15. general practitioner (family physician)

16. medical psychologist

17. health education instructor

18. healthcare organization and public health specialist

Table 1. Levels of Evidence (LoE) grading scale for diagnostic methods (diagnostic interventions)

Table 2. Scale for assessing the levels of evidence (LE) for prevention, treatment, and rehabilitation methods (preventive, therapeutic, and rehabilitative interventions)

Table 3. Scale for grading grades of recommendation (GR) for prevention, diagnostic, treatment, and rehabilitation methods (preventive, diagnostic, therapeutic, and rehabilitative interventions)

Procedure for updating clinical guidelines.

The mechanism for updating clinical guidelines provides for their systematic revision at least once every three years, as well as upon the emergence of new evidence-based medicine data on the diagnosis, treatment, prevention, and rehabilitation of specific diseases, or in the presence of justified additions/comments to previously approved clinical guidelines, but no more frequently than once every 6 months.

Appendix A3. Reference Materials

• Federal Law No. 52-FZ «On the Sanitary and Epidemiological Welfare of the Population» dated March 30, 1999 (latest edition)

• Federal Law No. 323-FZ «On the Fundamentals of Protecting the Health of Citizens in the Russian Federation» dated November 21, 2011

• Decree of the Government of the Russian Federation No. 555 dated May 5, 2018, «On the Unified State Health Information System».

• Letter of the Ministry of Health of the Russian Federation No. 18-2/0579 dated April 9, 2018, «On the Procedure for Organizing and Providing Medical Care Using Telemedicine Technologies

• Decree of the Government of the Russian Federation No. 789 dated October 16, 2000, «On Approval of the Rules for Determining the Degree of Loss of Professional Working Capacity Resulting from Industrial Accidents and Occupational Diseases».

• Order of the Ministry of Health of the Russian Federation No. 905n dated November 12, 2012, «On Approval of the Procedure for Providing Medical Care to the Population in the Profile "Otorhinolaryngology"";

• Order of the Ministry of Health of the Russian Federation No. 205n dated May 2, 2023, «On Approval of the Nomenclature of Positions for Medical and Pharmaceutical Workers».

• Order of the Ministry of Health of the Russian Federation No. 911n dated December 21, 2012, «On Approval of the Procedure for Providing Medical Care for Acute and Chronic Occupational Diseases».

• Order of the Ministry of Health of the Russian Federation No. 417n dated April 27, 2012, «On Approval of the List of Occupational Diseases».

• Federal Law No. 426-FZ «On Special Assessment of Working Conditions» dated December 28, 2013 (latest edition, 2016).

• Order of the Ministry of Health of the Russian Federation No. 178n dated April 9, 2015, «On Approval of the Procedure for Providing Medical Care to the Population in the Profile "Audiology and Otorhinolaryngology"".

• Order of the Ministry of Health of the Russian Federation No. 282n dated May 5, 2016, «On Approval of the Procedure for Conducting Expert Examination of Professional Suitability and the Form of the Medical Certificate on Fitness or Unfitness for Specific Types of Work».

• Order of the Ministry of Health of the Russian Federation No. 804n dated October 13, 2017, «On Approval of the Nomenclature of Medical Services». As amended on April 16, 2019, March 5, and September 24, 2020.

• Federal Law No. 489-FZ dated December 25, 2018, «On Amending Article 40 of the Federal Law "On Compulsory Medical Insurance in the Russian Federation" and the Federal Law "On the Fundamentals of Protecting the Health of Citizens in the Russian Federation" Regarding Clinical Guidelines»

• Federal Law No. 323-FZ dated November 21, 2011 (as amended on December 27, 2018) «On the Fundamentals of Protecting the Health of Citizens in the Russian Federation» (with amendments and additions, entered into force on January 31, 2019).

• Order of the Ministry of Labor and Social Protection of the Russian Federation No. 585n dated August 27, 2019, «On Classifications and Criteria Used in Carrying out Medical and Social Appraisal of Citizens by Federal State Medical and Social Appraisal Institutions».

• Directive of the Government of the Russian Federation No. 833-r dated April 26, 2019, «Complex of Measures to Encourage Employers and Employees to Improve Working Conditions and Preserve Workers' Health, as Well as to Motivate Citizens to Maintain a Healthy Lifestyle».

• Order of the Ministry of Health of the Russian Federation No. 36n dated January 31, 2019, «On Approval of the Procedure for Conducting Expert Examination of the Causation of a Disease with the Occupation and the Form of the Medical Certificate on the Presence or Absence of an Occupational Disease».

• Order of the Ministry of Health of the Russian Federation No. 104n dated February 28, 2019, «On Approval of the Procedure and Timelines for the Development and Revision of Clinical Guidelines, Their Standard Form, and Requirements for Their Structure, Content, and Scientific Validity of Information Included Therein» (as amended).

• Order of the Ministry of Health of the Russian Federation No. 103n dated February 28, 2019, «On Approval of the Procedure and Timelines for the Development and Revision of Clinical Guidelines, Their Standard Form, and Requirements for Their Structure, Content, and Scientific Validity of Information Included Therein»

• GOST ISO 9612-2016 Acoustics. Determination of occupational noise exposure. Engineering method. - Moscow: Standartinform. 2019. – 40 p.

• Order of the Ministry of Labor of Russia No. 687n dated September 30, 2020, «On Approval of the Criteria for Determining the Degree of Loss of Professional Working Capacity Resulting from Industrial Accidents and Occupational Diseases»

• Order of the Ministry of Labor of Russia No. 982n dated December 30, 2020, «On Approval of the Form of the Rehabilitation Program for Victims of Industrial Accidents and Occupational Diseases and the Procedure for Its Compilation»

• Order of the Ministry of Health of the Russian Federation No. 788n dated July 31, 2020, «On Approval of the Procedure for Organizing Medical Rehabilitation for Adults».

• Order of the Ministry of Health of the Russian Federation No. 1029n dated September 28, 2020, «On Approval of Lists of Medical Indications and Contraindications for Sanatorium-Resort Treatment».

• Order of the Ministry of Health of the Russian Federation No. 788n dated July 31, 2020, «On Approval of the Procedure for Organizing Medical Rehabilitation for Adults.

• Joint Order of the Ministry of Labor and Social Protection of the Russian Federation No. 988n and the Ministry of Health of the Russian Federation No. 1420n dated December 31, 2020, «On Approval of the List of Harmful and (or) Hazardous Production Factors and Jobs in Performing Which Mandatory Preliminary Medical Examinations upon Hiring and Periodic Medical Examinations Are Carried Out».

• Sanitary Rules 2.5.3650-20 «Sanitary and Epidemiological Requirements for Certain Types of Transport and Transport Infrastructure Facilities» (SP 2.5.3650-20).

• Hygienic Standards and Requirements for Ensuring Safety and (or) Harmlessness of Human Living Environment Factors. SanPiN 1.2.3685-21.

• Order of the Ministry of Health of the Russian Federation No. 29n dated January 28, 2021, «On Approval of the Procedure for Conducting Mandatory Preliminary and Periodic Medical Examinations of Workers Provided for by Part Four of Article 213 of the Labor Code of the Russian Federation, the List of Medical Contraindications to Carrying out Work with Harmful and (or) Hazardous Production Factors, as Well as Jobs for Which Mandatory Preliminary and Periodic Medical Examinations Are Carried Out».

• State Register of Medicines of the Ministry of Health of the Russian Federation. Edition of February 20, 2021.

• Interim Methodological Guidelines «Prevention, Diagnosis, and Treatment of the Novel Coronavirus Infection (COVID-19). Version 16 (August 18, 2022).

• Decree of the Government of the Russian Federation No. 1206 dated July 5, 2022, «On the Procedure for Investigating and Recording Cases of Occupational Diseases in Workers.

Appendix B. Physician Action Algorithms

Fig. 6 Algorithm for establishing a preliminary diagnosis of an occupational auditory system disease

Notes to Appendix B1:

The preliminary diagnosis of noise-induced hearing loss is initiated during periodic medical examinations (PME) and/or when a worker independently consults an otorhinolaryngologist at any medical institution. During the PME, the medical commission's otorhinolaryngologist must review the information on workplace hazards indicated in the worker's medical examination referral. Based on the information contained in the nominal list, the physician must determine whether the worker is exposed to occupational noise exceeding the maximum permissible concentration (MPC), as well as the occupation and duration of the examinee's occupational tenure. The probability of developing noise-induced hearing loss exists if the worker has been exposed to noise levels exceeding the MPC for a prolonged period (at least 8–10 years). During the employee's PME and/or patient consultation, the otorhinolaryngologist must collect complaints, inquire about the nature of the work, clarify the presence of noise at the current workplace, and determine the duration of noise exposure throughout the entire employment history. In all cases, it is necessary to thoroughly interview the worker about previous occupations and determine the duration of occupational noise exposure (in total, or—in case of work interruptions—the duration of the last continuous period of work in noise). In addition, it is necessary to clarify the presence of vibration, ototoxic harmful agents, a heating microclimate, and psycho-emotional stress at the workplace. During routine ENT examination (rhino-, pharyngo-, laryngoscopy, otoscopy), special attention should be paid to the condition of the tympanic membrane (to exclude inflammatory and sclerotic changes in middle ear structures). All individuals working under conditions of occupational noise exposure or being hired for jobs involving noise exposure—both during the PME and upon independent consultation with a physician—undergo tone audiometry and, when indicated, vestibular function testing. Audiometric testing for individuals working under occupational noise conditions is performed no earlier than 14 hours after cessation of noise exposure to exclude the effect of temporary threshold shift (TTS) on the test results. Since standard pure-tone audiometry indicators serve as the starting point for determining the direction of further examination, establishing a diagnosis, and resolving the issue of the worker's occupational fitness, it is extremely important to ensure the reliability of the study. The medical commission's otorhinolaryngologist draws up a conclusion based on the audiogram protocol, formulates a diagnosis in accordance with ICD-10, indicates the disease code, and evaluates the presence of medical contraindications for work specified in the current PME regulations. Differential diagnosis is not performed during the PME due to the lack of comprehensive information at the medical examination regarding working conditions, medical history, past illnesses, disease development and progression, and the possibility of performing additional audiological tests. Based on the PME results, groups for further dynamic (dispensary) follow-up are formed. When signs of noise effects on the hearing organ are recorded on audiometry, the conclusion is formulated as follows: ICD-10 (Z57.0) – "Occupational noise exposure (signs of noise effects on the hearing organ)." In this case, the worker has no occupational fitness restrictions. They are included in the high-risk group for occupational disease development, and an individual hearing rehabilitation program should be developed for them. Signs of noise effects on the hearing organ, in the strict sense of the word, represent a prenosological condition and do not constitute a disease in the full sense of the word. The otorhinolaryngologist should classify workers with bilateral chronic sensorineural hearing loss featuring an audiometric pattern typical of an occupational disease among individuals with suspected occupational disease ("Noise-induced hearing loss") if the following requirements are met: at a workplace noise level up to 90 dBA – a work tenure of 15 years or more; at a workplace noise level exceeding 90 dBA – a work tenure of 10 years or more. The occupational health physician, acting as the chairman of the medical commission, analyzes the information and makes a decision to submit a notification of a preliminary diagnosis of a chronic occupational disease to the territorial Rospotrebnadzor institution. Example of preliminary diagnosis formulations:

1. «Adverse effects of occupational noise (signs of noise impact on the auditory system» ICD-10 (Z57.0

2. Noise-induced hearing loss (chronic bilateral sensorineural hearing loss, grade ______) – preliminary diagnosis of an occupational disease (notification dated "__" ______ 20__, ref. no. ___), ICD-10 (H83.3).

Upon establishing a preliminary diagnosis of an occupational hearing disorder, the worker must be referred within 30 days for outpatient or inpatient examination to a territorial or departmental occupational pathology center (OPC) or another specialized occupational health medical organization licensed to perform activities in "Occupational Pathology", "Expertise of the causal link between the disease and profession", and "Expertise of occupational fitness", to provide specialized occupational health care, conduct an expertise on the causal link between the hearing disorder and the profession, establish a final diagnosis, and develop an individual rehabilitation program (IRP) for hearing. The expertise of occupational fitness is carried out in accordance with regulatory documents defining the procedure for this type of expertise. The establishment of a preliminary diagnosis of occupational sensorineural hearing loss concludes with the submission of a notification of the preliminary diagnosis of a chronic occupational hearing disorder to the Rospotrebnadzor authority and the referral of the patient to the OPC.

Fig. 7 Flowchart of the algorithm for establishing a final diagnosis of an occupational hearing disorder

Explanations to algorithm B II

The final diagnosis of an occupational hearing disorder is established at the Occupational Pathology Center (OPC). The initial patient examination at the OPC begins with an analysis of the occupational route and working conditions based on the information provided in the worker's sanitary and hygienic characteristics (SHC) of working conditions. The priority criterion determining the development of noise-induced hearing loss is the noise level at the workplace. The higher it is, the greater the probability of disease development. The next important criterion is the duration of continuous work tenure in contact with noise levels exceeding the MPC. The presence of work interruptions, especially prolonged ones, reduces the likelihood of disease progression. Consideration of the link between the hearing disorder and the profession in the post-exposure period (after cessation of work in noise) is possible only if there is documentary confirmation of hearing loss development during the period of work under noise exposure. The onset or progression of chronic sensorineural hearing loss in the post-exposure period of noise is not a grounds for considering the occupational nature of the disease. When analyzing the SHC, the occupational health physician must also evaluate the completeness and quality of the information presented therein. Expert assessment of the occupational origin of a disease is not permitted if the SHC contains incorrect, incomplete, or erroneous information. In this case, the OPC occupational health physician requests additional information on working conditions from the territorial Rospotrebnadzor authorities. Clinical examination of a worker in a "noise-hazardous" profession at the OPC begins with reviewing the medical and occupational history. First, it is necessary to clarify the potential link between hearing loss and past acute or chronic inflammatory ear diseases, infectious diseases, intoxications, head or ear injuries, treatment with ototoxic drugs, and the presence of other (non-occupational) risk factors. Second, important information is the rate of hearing loss progression: if the disease is caused by occupational noise exposure, it progresses slowly, or—having developed to the first degree of hearing loss—may not progress, and hearing thresholds remain stable for a long time. Third, it is necessary to determine the presence of comorbid pathology that may be one of the causes or even the sole cause of hearing loss (arterial hypertension, diabetes mellitus, lipid metabolism disorders, overweight, cervical spine osteoarthrosis, etc.). For these purposes, consultations with a general practitioner, neurologist, ophthalmologist, and endocrinologist are carried out. During the OPC examination, a general clinical assessment is performed: general (clinical) urinalysis, complete blood count with differential, general clinical blood biochemistry, biochemical analysis for lipid metabolism disorders (total cholesterol, HDL and LDL cholesterol, triglycerides, atherogenic coefficient), and ECG. When necessary – radiography of the cervical spine and paranasal sinuses, duplex/triplex scanning of extracerebral branches of brachiocephalic arteries, temporal bone CT and temporal bone CT with intravenous bolus contrast enhancement, skull bone MRI, and MRI of the vestibulocochlear organ for differential diagnosis and determination of the topography of the pathological process.

Hearing tests with tuning forks are performed using generally accepted methods. Tuning fork test data are primarily necessary for the differential diagnosis between conductive and sensorineural hearing loss. They cannot be used to determine the degree of hearing loss and work capacity in workers of "noise-hazardous" professions with hearing impairments. The main diagnostic method for occupational hearing loss is pure-tone threshold audiometry in the conventional frequency range, the advantages of which include strict dosing of the delivered signal, allowing the test results to be compared with previously obtained data. Pure-tone threshold audiometry provides a qualitative and quantitative assessment of auditory function across the entire frequency range, for both air conduction and bone conduction. Suprathreshold audiometry methods complement the results of pure-tone audiometry and serve as supportive indicators in the differential diagnosis of the type of hearing loss. Typically, the following tests are used: measurement of the difference limen for intensity (Lüscher test), determination of the uncomfortable loudness level, and the SISI test. Extended high-frequency pure-tone audiometry allows for the detection of early hearing changes not captured by other methods, primarily affecting the sensorineural part of the auditory analyzer. Speech audiometry using complex sound stimuli with continuously varying acoustic parameters is used to determine the speech reception threshold in certain professions; however, due to the subjectivity of evaluation, it does not hold major expert significance and is used to determine fitness for work, for example, in civil aviation. When assessing the occupational causality of a disease, acoustic immittance testing is mandatory, as it helps differentiate various forms of hearing loss, thereby increasing the reliability of topical diagnosis within the auditory analyzer. Two types of acoustic immittance are used: tympanometry and acoustic reflexometry. All patients undergo otoacoustic emissions testing: DPOAE and TEOAE. The information obtained from otoacoustic emissions reflects the functional state of outer hair cells from the base to the apex of the cochlea, although it is not an audiogram in the conventional sense. In complex diagnostic cases, additional test methods are used (ABR and ASSR tests). ABR and ASSR testing are objective diagnostic methods used in cases of difficult differential diagnosis, including to resolve discrepancies between subjective and objective data during expert evaluations. All test results regarding auditory function are evaluated by an otorhinolaryngologist-audiologist. If differential diagnosis requires it, a vestibular examination is performed to assess vestibular function. The results are evaluated based on the characteristics of nystagmus and autonomic bodily reactions. Based on the obtained examination results, a clinical diagnosis is formulated in accordance with the classification presented in section 1.5. Upon establishing that an employee has bilateral chronic sensorineural hearing loss of any severity, an otorhinolaryngologist or otorhinolaryngologist-audiologist holding a valid certification in occupational medicine shall prepare the documents in the prescribed manner for review by the medical commission (MC) to establish the final diagnosis and conduct the expert assessment of the causal relationship between the auditory organ disorder and the occupation. If no causal link is found between the occupational noise affecting the employee and the state of their auditory organ, the MC issues a decision stating that the patient does not have an occupational hearing disorder. When assessing the occupational causality of an auditory organ disorder, the final diagnosis of an occupational hearing disorder must be formulated as follows:

1. ICD-10 (Z57.0) - Adverse effects of occupational noise (signs of noise effects on the hearing organ): "Fit for work without restrictions." - ICD-10 (H83.3).

2. Noise-induced hearing loss (chronic bilateral sensorineural hearing loss, grade 1 "A"). Occupational disease, newly established (confirmed or modified). "Fit for the profession subject to dynamic monitoring at the occupational pathology center once a year." - ICD-10 (H83.3). Hearing IRP developed.

3. Noise-induced hearing loss (chronic bilateral sensorineural hearing loss, grade 1 "B"). Occupational disease, newly established (confirmed or modified). "Fit for the profession subject to dynamic monitoring at the occupational pathology center twice a year. The worker is informed about the increased health risk if they continue working in noise conditions exceeding the maximum permissible level (80 dBA)." - ICD-10 (H83.3). Hearing IRP developed.

4. Noise-induced hearing loss (chronic bilateral sensorineural hearing loss, grade 2 or higher). Occupational disease, newly established (confirmed or modified). Work in contact with noise levels exceeding the maximum permissible level (80 dBA) is contraindicated. Referral for ITU (medical and social expertise) is indicated. Further monitoring and treatment at the place of residence or affiliation.

The Medical Commission (MC) decision is formalized as a protocol indicating the newly established (confirmed or modified) final diagnosis of the occupational disease of the hearing organ. The commission is obliged to draw up a reasoned justification for the decision made. Regardless of the decision made, the MC protocol indicates the therapeutic and preventive measures necessary to prevent the progression of hearing impairment, draws up a hearing IRP, and provides labor recommendations. When establishing a final diagnosis of an occupational hearing disorder, a notification is sent to the territorial Rospotrebnadzor institution, the employer, the insurer, and the healthcare institution that referred the patient. Issues of further occupational fitness and the amount of financial compensation for the occupational disease are resolved within the framework of ITU institutions.

Appendix C. Patient Information

At the first presentation of a patient complaining of tinnitus, head noise, or hearing loss, they must be informed of the importance of a comprehensive diagnostic stage, as these complaints can be a manifestation of a wide variety of diseases. Persistent treatment without differential diagnostic measures can be erroneous (for example, in the treatment of certain conditions accompanied by tinnitus or hearing loss [acoustic neuroma], the use of vitamins, nootropics, and physiotherapy can provoke accelerated tumor growth). An examination plan is drawn up involving various specialists based on the collection of complaints and medical history. Following a comprehensive audiological examination, if a lesion of a specific level of the auditory system is identified, additional research methods are prescribed to verify the diagnosis. In accordance with the established nosological form, a treatment and rehabilitation plan is proposed. The use of visualization methods (primarily CT and MRI of the temporal bones and brain) makes it possible to exclude the development of diseases requiring treatment by specialists of another profile (neurosurgeons, neurologists). The results of the examination and consultations with related specialists determine the indications for medical treatment of the developing pathology of the auditory analyzer, and a discussion is held on adopting individual measures to reduce the risk of noise exposure on the body. Treatment prospects, potential side effects, and the importance of implementing the hearing IRP are also discussed with the patient.

Appendix G. Assessment Scales, Questionnaires, and Other Evaluation Tools

Appendix G1. Method for determining the group excess risk of noise-induced hearing loss to justify preventive measures

Sources: 41-44

Type

Calculation method for determining the group excess risk of noise-induced hearing loss based on the following initial data:

- gender,

- age,

- length of service,

- occupational noise exposure (equivalent A-weighted sound level).

Indication

Determination of the group excess risk of hearing loss from noise exposure to justify specific measures for the primary prevention of hearing function disorders.

Content (template):

The application of mathematical models for predicting the effect of occupational vibroacoustic factors on the health of workers in "noise-hazardous" industries allows assessing the risk of hearing impairment from noise exposure and timely implementing preventive measures aimed at preserving and strengthening workers' health.

The probability of noise-induced hearing loss determines the attributable or excess risk of damage to the hearing organ, which is numerically equal to the difference in absolute risks in homogeneous population groups of individuals exposed and unexposed to noise [41, 42].

The magnitude of the excess risk of noise-induced hearing loss in a homogeneous population group (gender, age, length of service, occupational noise exposure) according to specified indicators and hearing loss criteria is calculated using mathematical models based on the provisions of international standards ISO 7029 and ISO 1999 [43, 44].

Key (interpretation:

To determine the excess risk of noise-induced hearing loss, an indicator in the form of the mean binaural hearing threshold at audiometric frequencies of 0.5, 1.0, 2.0, and 3.0 kHz at a 30 dB criterion should be used (Fig. 8).

To determine the excess risk of early signs of noise effects on the hearing organ, an indicator in the form of the mean binaural hearing threshold at audiometric frequencies of 4.0 and 6.0 kHz at a 20 dB criterion should be used (Fig. 9).

Explanations

Methods for calculating age-related changes in hearing thresholds and noise-induced hearing loss are based on many years of audiological and epidemiological studies reflected in international standards ISO 7029 and ISO 1999 starting from 1974, which are periodically updated (the latest editions are ISO 7029:2017 and ISO 1999:2013). The accuracy of the method and its operating range are determined by a number of normal distribution coefficients (the mentioned standards use a range of coefficients from 5 to 95% with a 1% step).

The choice of the indicator for determining the excess risk of hearing loss in the form of the mean binaural hearing threshold at audiometric frequencies of 0.5, 1.0, 2.0, and 3.0 kHz is based on the provisions of the ILO Guidelines for Maritime Seafarers' Medical Examination, and the 30 dB criterion is determined by studies [37].

The choice of the indicator for determining the excess risk of early signs of noise effects on the hearing organ in the form of the mean binaural hearing threshold at audiometric frequencies of 4.0 and 6.0 kHz at a 20 dB criterion is determined by studies [37].

Fig. 8 Determination of the excess risk of hearing loss for 60-year-old men with 40 years of work in noise at 90 dBA, based on the mean binaural hearing threshold at audiometric frequencies of 0.5, 1.0, 2.0, and 3.0 kHz (HTLA(m) – distribution of probable hearing thresholds for 60-year-old men; HTLAN(m) – distribution of probable hearing thresholds for 60-year-old men with 40 years of work in noise at 90 dBA; HILC-30 [КрПС-30] – hearing loss risk criterion of 30 dB; ER – magnitude of excess risk – 8%).

Fig. 9. Determination of the excess risk of early signs of noise-induced hearing loss for 25-year-old males with 20 years of noise exposure at 90 dBA, based on the mean binaural hearing threshold at audiometric frequencies of 4.0 and 6.0 kHz (HTLA (m) – distribution of probable hearing thresholds for 25-year-old males; HTLAN (m) – distribution of probable hearing thresholds for 25-year-old males with 20 years of noise exposure at 90 dBA; HTR-20 – criterion for determining the risk of early signs of noise-induced hearing loss of 20 dB; ER – excess risk value of 41%).