1. Introduction

The effectiveness of cochlear implantation in the rehabilitation of patients with severe hearing loss and deafness has been proven by numerous studies [1,4,7,12]. The effectiveness of auditory-speech rehabilitation in terms of improving the quality of perceived acoustic information has been shown in a number of audiological studies [2,4,11].

Thus, most of the research in the field of cochlear implantation is concentrated in the field of audiology. However, CI affects not only the ability to distinguish sounds, products and intelligibility of syllables, words, phrases and sentences, but also affects such an important aspect of life as the social functioning of the individual. In order to objectively determine the impact of CI on the formation of social ties “man-society”, batteries of tests were proposed to determine the quality of life associated with the state of human health [3]. It should be emphasized that the focus should remain on the social and emotional status of patients after cochlear implantation [9]. The first studies on the quality of life in patients after CI were conducted in the late 1980s. through a written questionnaire, where adult users of cochlear implantation systems described its advantages and disadvantages [16].

2. Materials and Methods

The quality of life of a person (individual or society) is an evaluation category of a person’s life, which generally characterizes the parameters of all components of his life: life potential, life activity and living conditions (tools, resources and environment) in relation to some objective or subjective standard [8]. In practice, there are several approaches to assessing QoL: physiological, economic [7], sociological, psychological, and medical, which also includes the concept of quality of life associated with the state of human health. There are the following criteria for QoL [5]:

1) physical (vitality, energy, fatigue, pain, discomfort, sleep, rest, sexual activity);

2) psychological (positive and negative emotions, cognitive functions, self-esteem, appearance, mobility);

3) level of independence (working capacity, daily activities, dependence on drugs and treatment);

4) social life (personal relationships, social value of the subject);

5) environment (life, safety, well-being, availability and quality of medical and social care, security, ecology, learning opportunities, information availability);

6) spirituality (religion, personal beliefs).

The quality of life is determined by “the physical, social and emotional factors of the patient's life that are important for him to exist and directly affect him”. This formulation is based on the WHO tiered definition of health and represents health as “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”. There is a separation of the concepts of “quality of life” - QoL (Quality of Life) and "quality of life associated with the state of health" - HR-QoL (Heath Related Quality of Life). The active work of international research groups resulted in a consensus regarding the standardized study of patients' opinions about their health as a monitoring of the results of health care efforts [12].

The ultimate goal of any healthcare-related initiative today should be considered to be the achievement of a higher quality of life for patients, along with the preservation of their working capacity and well-being [13]. In order to standardize respondents' opinions about their own health, general and specific questionnaires were developed. Collecting standard responses to standard questions proved to be the most effective method for assessing health status. Carefully formulated questions and selected answers, compiled for calculation by the summation of ratings, formed the basis of modern QoL questionnaires. Today, more than 50 variants of questionnaires are used in the world to assess QoL. There are general and specific questionnaires to determine the quality of life of the population.

General questionnaires are aimed at assessing the health of the population as a whole, regardless of pathology, and specific questionnaires - for specific diseases. The advantage of general questionnaires is that their validity (significance, relevance, adequacy) has been established for a wide variety of nosologies, which allows for a comparative assessment of the impact of various medical programs on QoL of both individual subjects and the entire population. The disadvantage of such instruments is their inadequate sensitivity to changes in health status within a single disease. It is advisable to use general questionnaires to assess healthcare tactics in general and when conducting epidemiological studies. When using a general questionnaire, a selection indicator (preference based measures) can be determined. This indicator characterizes the combined influence of physical, emotional and social factors on QoL. Thus, the overall indicator correlates with the health status or level of well-being of the individual. The advantage of sample indicators is that they can be used to calculate the number of qualitatively saved years of life for pharmacoeconomic analysis (costeffectiveness, costutility).

Specific questionnaires focus on a specific nosology and its treatment. They make it possible to detect minimal changes in the QoL of patients that have occurred over a relatively short period of time, usually 2-4 weeks. Specific questionnaires are used to assess the effectiveness of a particular method of managing patients and treating a given disease, they are used in clinical trials of pharmacological drugs.

There are no uniform criteria and standard norms for QoL. Each questionnaire has its own criteria and rating scale. For various groups, regions and countries, it is possible to determine the conditional norm of QoL, and in the future to compare with this indicator. Questionnaires make it possible to identify only trends in changes in QoL in a particular group of respondents. Questionnaires are subject to strict requirements [14]. They should be:

1) universal (cover all health parameters);

2) reliable (fix individual health levels for different respondents);

3) sensitive to clinically significant changes in the health status of each respondent;

4) reproducible (test = retest);

5) easy to use and concise;

6) standardized (to offer a single version of standard questions and answers for all groups of respondents);

7) evaluation (to quantify health parameters).

There is a certain terminology used to describe questionnaires. Sensitivity - the ability of the method to determine clinically significant (relevant) changes even with a small severity of changes. Reliability - the ability of the method under the same conditions, with the same type of treatment to give the same results in repeated studies. The term “validity” (relevance, significance, adequacy) is used to determine the conformity of the results of the studied test with the results of a standard application (ie, an existing standard). There are several types of validity: external - obvious compliance with the standard (reference) quality, which is determined by existing ideas about it; meaningful - compliance of the composition and design of the applied test with the measured quality; distinctive - the ability of the test to distinguish between individuals and groups of people with distinctive qualities or in different states; criterion (diagnostic) - the ability of the test to measure the required property; interpretive - the degree of correctness of the conclusions; validity by simultaneity - comparison of the results on the test being studied with the reference estimates at the moment, i.e. without taking into account the initial differences of people and the individual different effect of training (training); validity by correspondence - comparison of the studied test with the results of a reference one, which has a previously known value; validity of a constructive whole, etc. The validity of a constructive whole is understood as the ability to display the studied qualities by a set of tests.

General and specific questionnaires are a tool for studying the quality of life associated with a state of health. In foreign literature, general questionnaires are distinguished: 36 Item Short Form Survey (SF-36) [15], Glasgow Benefit Inventory (GBI) - designed to identify changes in health as a result of treatment in the field of otorhinolaryngology [4], Glasgow Health Status Inventory (GHSI), reflecting the impact of health problems on a person's quality of life [11], Hearing Participation Scale (HPS) [6] - a simplified form of the GHSI questionnaire; Health Utilities Index (HUI), which is used to a greater extent to assess the material costs and economic benefits of various types of medical manipulations [6]; Assessment of Quality of Life (AQoL) [8].

Among the specific questionnaires for determining the quality of life associated with the state of health in patients after cochlear implantation, foreign literature mentions Patient Quality of Life Form (PQLF), Index Relative Questionnaire Form (IRQF), Performance Inventory for Profound Hearing Loss Answer Form (PIPHL) and Nijmegen Cochlear Implant Questionnaire (NCIQ). The PQLF and IRQF questionnaires were developed by the Ear Institute (Los Angeles, USA) [10]. The IRQF questionnaire reflects information received from relatives and (or) relatives regarding the patient's lifestyle, his social activity and adaptation to the cochlear implant. PIPHL shows the patient's attitude to communication situations in a daily setting and can also be used in patients suffering from hearing loss [5]. NCIQ at this stage is the main questionnaire of the quality of life of English-speaking patients after cochlear implantation; its validity, reliability and sensitivity were confirmed [16].

Today, two adapted general questionnaires for assessing the quality of life associated with the health status of people with hearing impairment are used in Russia - SF-36 and WHOQOL-100 (World Health Organization quality of life questionnaire).

One of the most common general questionnaires for assessing the quality of life is SF-36, which is used in many European countries and in the USA [9]. The Russian version of SF-36 was proposed by the International Center for Quality of Life Research [7]: the reliability, validity and sensitivity of the method were confirmed [1]. Among the advantages of this questionnaire, there is a comprehensive assessment of the quality of life of respondents, as well as the possibility of assessing the quality of life of patients with any nosology. SF-36 consists of 36 questions grouped into eight scales.

3. Result and Discussion

1. Physical Functioning - Physical Functioning (PF) - a scale that assesses physical activity, including self-care, walking, climbing stairs, carrying heavy loads, as well as performing significant physical exertion. The scale indicator reflects the volume of daily physical activity, which is not limited by the state of health: the higher it is, the more physical activity, according to the subject, he can perform. Low scores on this scale indicate that physical activity is significantly health-limited.

2. Role Physical Functioning - Role Functioning/Physical (RP) - a scale that reflects the role of physical problems in limiting life, reflects the degree to which health limits the performance of normal activities. Low scores on this scale indicate that daily activities are significantly limited by physical health.

3. Role emotional functioning - Role Functioning / Emotional (RE) - involves assessing the degree to which the patient's emotional state interferes with the performance of work or any other type of daily activity.

4. The scale of viability - Vitality (VT) - implies the respondent's own assessment of the feeling. Low scores indicate fatigue of the subjects, a decrease in their vital activity.

5. Emotional state - Emotional Well-being (EW) - characterizes mood, determines the presence of depression, anxiety, evaluates the overall indicator of positive emotions. Low rates indicate the presence of depressive, anxiety states, psychological distress.

6. The scale of social functioning - Social Functioning (SF) - assesses satisfaction with the level of social activity (communication with friends, family, neighbors and colleagues) and reflects the degree to which the respondent's physical or emotional state limits them. Low values of the scale correspond to a significant limitation of social contacts, a decrease in the level of communication due to a deterioration in health.

7. Pain Scale - Bodily Pain (BP) - assesses the intensity of pain syndrome and its impact on the ability to actively function, including housework and outside work during the last month. Low scale values indicate that pain significantly limits the physical activity of the subjects.

8. Scale "General health" - General Health (GH) - assesses the state of health at the moment, the prospects for treatment and disease resistance: the higher the score, the better the health of the respondent.

For all scales in the complete absence of restrictions or health disorders, the maximum value is 100. Before calculating the indicators of eight scales, the recoding is carried out, the summation of the answers according to the methodology presented by the authors of SF-36. Next, the average values for each scale are calculated. The higher the score on each of the scales, the better the quality of life for this parameter.

The WHO Quality of Life Measurement Tool (WQOL-100) is a self-administered questionnaire that asks questions about how they perceive various aspects of their lives [12].

WHOQOL-100 is the result of a five-year work of an international team of experts - physicians, psychologists, sociologists. It was developed simultaneously in the main languages of the world in 15 research centers in Europe, Australia, Asia and Africa.

North and Central America, in countries with different economic levels and different cultural traditions. Thanks to a unified development methodology (WHOQOL Group, 1993) and coordination of development centers at all stages, the tool is universal and allows for cross-cultural comparisons.

An additional tool in evaluating the effectiveness of auditory rehabilitation of cochlear implant users in various acoustic situations is the Cochlear Implant Function Index (CIFI) questionnaire, proposed by a team of American scientists in 2009 [12]. The IFCI questionnaire consists of 22 questions grouped into six scales: “use of visual reinforcement”, “the ability to communicate by phone”, “communication at work/study”, “speech perception in background noise”, “speech perception in a group of people”, “speech perception in large audiences”. From the proposed options “always”, “often”, “sometimes”, “rarely” and “never” the respondents were asked to choose the most optimal answer. The assessment of the results of the survey was carried out according to the Gutmann scale, or the cumulative scaling method [8].

Hearing loss is one of the most common congenital anomalies [3]. According to the 2nd International Conference on Newborn Hearing Screening Diagnosis and Intervention (2002), hearing impairment occurs in 2-3 out of 1000 newborns, which is twice as high as the incidence of non-union of the lip (sky), ten times - than the frequency of phenylketonuria. In the treatment of hearing loss, a large arsenal of surgical, medical and physiotherapeutic means is used. Insufficient efficiency and high cost of drug therapy for various forms of hearing loss predetermine the search for modern methods of treatment, the development of new approaches to the social adaptation of people with hearing loss. The first plan is the rehabilitation of such patients. In the case of bilateral sensorineural hearing loss of the IV degree and deafness, even multiply amplified sound does not create auditory sensations in a person, therefore, it is undeniable that cochlear implantation at the present stage is the method of choice in the rehabilitation of patients with a high degree of hearing loss and deafness. Hearing is an integral part of the adequate functioning of the individual: it is he who forms speech, and therefore participates in the development of intellectual abilities, social and emotional functioning in the world of hearing people [15]. In addition to the ability to perceive acoustic information through the CI system for deaf patients, it also achieves a sufficient level of communication skills, which positively affects the quality of life of patients.

4. Conclusions

Thus, it follows that among the global trends in the field of improving cochlear implantation systems, the use of electroacoustic stimulation in patients with residual perception of low-frequency sounds, a new approach that uses sparing surgery in order to minimize trauma to the apex of the cochlea, while maintaining hearing, comes to the fore. patient at low frequencies. In addition, the following areas in audiology, otosurgery and hearing and speech rehabilitation are promising: the introduction of fully implantable cochlear implantation systems; development of new strategies for speech coding, improvement of sound processing technologies with microphones, as well as the search for new surgical approaches when installing a cochlear implant.