Bronchial Asthma in Children of Chita: Prevalence and the Role of Autonomic Dysregulation in Its Development

The study is devoted to the analysis of the prevalence of bronchial asthma among the child population of the city of Chita and the assessment of the role of autonomic dysregulation in the pathogenesis of this disease. The methodology of the international program "ISAAC" (International Study of Asthma and Allergy in Childhood), which allows standardized assessment of the prevalence of bronchial asthma, allergic rhinitis, and atopic dermatitis in children living in various regions and ecological conditions, was used in the work. Comprehensive examination included spirometry, peak flowmetry with an exercise challenge, and cardiointervalography, which made it possible to assess the state of lung ventilation function and the autonomic nervous system in healthy children, the risk group, and patients with bronchial asthma.

It was established that the true prevalence of bronchial asthma among children of Chita is 3.6%, which significantly exceeds the data of statistical reporting. Mild forms of the disease course predominate in the structure of the pathology. A connection between bronchial asthma and allergic rhinitis and atopic dermatitis was identified. The results indicate the presence of autonomic dysfunction in children at risk, characterized by impaired adaptive mechanisms of the cardiovascular system to stress impacts, which points to the role of autonomic dysregulation in the formation of bronchial asthma at early stages of disease development.

Relevance. Allergic diseases are among the leading problems of modern pediatrics. Bronchial asthma occupies the first place in terms of prevalence, severity, potential disability, and danger to life [51]. According to official statistics, the number of children suffering from this pathology has increased almost threefold over the last ten years [97]. Studies conducted in recent years in various regions of Russia have shown that official statistics do not always reflect the true picture of the prevalence of allergic diseases in our country [30, 33, 45]. Late diagnosis leads to increasing severity of the disease course, disability, and ineffectiveness of therapy. Conducting an epidemiological study according to the standardized international program "ISAAC" ("International Study of Asthma and Allergy in Childhood") makes it possible to determine the true prevalence not only of bronchial asthma, but also of allergic rhinitis and atopic dermatitis in children living in various regions and ecological conditions. This is of great importance in forming risk groups and determining the strategy for preventing these diseases [107]. Preliminary studies in Zabaykalye were conducted according to the "ISAAC" program [34a]. They showed the need for in-depth clinical-functional examination of children in order to early diagnosis of bronchial asthma and timely detection of symptoms of allergic rhinitis and atopic dermatitis. This will make it possible to begin adequate therapy, significantly reduce the number of severe forms, their socio-economic consequences, and lead to an improvement in the quality of life of patients. The basis of bronchial asthma in children is chronic allergic inflammation of the bronchial mucosa caused by an immune response to the action of an exogenous allergen [20]. However, it is well known that immune reactions in the human body are closely linked with the functioning of the nervous and endocrine systems. The emergence of dysregulation in these systems is one of the most important pathological conditions [41].

Pathogenetic Mechanisms of Development. Clinical observations and scientific research testify to the significant role of autonomic nervous system dysfunction in the formation and course of bronchial asthma. The autonomic contour of the nervous system ensures the adaptation of the organism to the action of environmental factors through direct control of the function of various organs and systems. It is known that in children suffering from bronchial asthma, functional impairments of this system exist, manifesting as dysregulation of both the local and central contours [24, 26, 78, 79, 109, 121]. This contributes to the formation of a pathological system that has maladaptive significance. Clinically, this manifests as impaired function not only of the respiratory, but also of the cardiovascular systems. Most studies are devoted to the study of dysregulatory impairments of the autonomic nervous system exclusively in children with an established diagnosis of asthma [78, 79, 109, 121]. However, processes of maladaptation of the organism can arise under the influence of a number of factors at various stages of bronchial asthma development. There are isolated data on the role of autonomic dysregulation in this process [108, 175]. Studying the state of the autonomic nervous system in healthy children and children at risk will make it possible to create a more complete picture of the mechanisms of disease development. In this regard, a comprehensive study of lung ventilation indicators, bronchial hyperreactivity in relation to the functional activity of the autonomic nervous system in children at various stages of bronchial asthma formation contributes to a deeper understanding of the role of dysregulatory mechanisms in the pathogenesis of this disease.

Goal: to determine the prevalence of bronchial asthma among the child population of Chita and, based on a comprehensive study of the ventilation function of the lungs and the autonomic nervous system, to determine the significance of dysregulatory mechanisms in the formation of this disease.

Tasks:

1. To determine the prevalence of bronchial asthma with symptoms of allergic rhinitis and atopic dermatitis among children of Chita.

2. To study the state of external respiration function and bronchial reactivity in healthy children, the risk group, and patients with bronchial asthma.

3. To determine the main dysregulatory mechanisms of functioning of the autonomic nervous system in children at risk and patients with bronchial asthma.

4. To identify and assess the nature of correlational relationships between cardiointervalography indicators and lung ventilation function in healthy children, the risk group, and patients with bronchial asthma.

Theses for Defense:

1. The prevalence of bronchial asthma among children of Chita, according to the epidemiological study conducted according to the "ISAAC" program, is 3.6%. In the structure of the pathology, mild forms of the disease course predominate. A combination of bronchial asthma symptoms with symptoms of allergic rhinitis was identified in 7.6% of cases, and symptoms of atopic dermatitis in 3.3% of children.

2. Signs of initial bronchial hyperreactivity are detected in 10% of healthy children by peak flowmetry with an exercise challenge. The study of external respiration function by the "flow-volume" method in the risk group and in sick children confirms that a decrease in FEV1 and MEF50 is the most significant for diagnosing bronchial asthma in children at early stages of disease development.

3. The state of the autonomic nervous system in children at risk is characterized by tension of the regulatory mechanisms of cardiovascular system activity. With the development of bronchial asthma, initial transient vagotonia with subsequent sympathotonic disruption of the recovery processes of cardiovascular system function.

Scientific Novelty:

For the first time in the city of Chita, the prevalence of symptoms of bronchial asthma, allergic rhinitis, and atopic dermatitis was investigated in accordance with the requirements of the international program for the study of asthma and allergy "ISAAC". The true prevalence of bronchial asthma in children was established at 3.6%, which is seven times higher than the statistical reporting data of 2002 (0.48%). Underdiagnosis is predominantly associated with insufficient detection of mild forms of the disease course. On the basis of a comprehensive approach, the presence of autonomic dysfunction in children at risk and patients with bronchial asthma was established. It is characterized by an inadequate response to stress impacts and is compensated by adequate recovery in the pre-disease stage. Priority in the work was given to a comprehensive assessment of cardiointervalography indicators and external respiration function in patients with bronchial asthma, which showed the presence in them of interrelated disorders in the activity of the cardiovascular and respiratory systems at the level of the peripheral contour of autonomic function regulation.

Theoretical and Practical Significance:

The epidemiological study conducted according to the "ISAAC" program made it possible to determine the true prevalence of bronchial asthma among the child population of the city of Chita, which provides the opportunity to timely identify previously undiagnosed diseases and conduct prophylaxis and etiopathogenetic therapy of the pathological process. Determining the prevalence of allergic rhinitis and atopic dermatitis makes it possible to form a risk group in which the conduct of preventive measures contributes to preventing the progression of atopic diseases. The peak flowmetry method combined with physical exercise, due to high specificity, can be used for identifying individuals with bronchial hyperreactivity in the healthy population during comprehensive examination. The study of the state of the autonomic nervous system in children at risk makes it possible to identify children with inadequate adaptation of the cardiovascular system to irritating factors of the external environment and to conduct preventive measures to prevent the development of bronchial asthma. The conducted research expanded the knowledge of the pathogenesis of bronchial asthma. Disorders of the regulatory autonomic contour of the nervous system are formed in the risk group and are associated with impaired adaptive capabilities of the child's organism to the action of stress factors. Moreover, with the development of the disease, medium-strength correlations between the cardiovascular and respiratory systems are formed at the level of the peripheral contour of the autonomic nervous system. This shows that the cardiovascular system is involved in the pathological process in bronchial asthma at early stages of the disease.

Implementation in Practice:

The results of the epidemiological study were implemented in the work of the City Children's Polyclinic No. 3, in the educational process of the Department of Pediatric Diseases of the Chita State Medical Academy.

10 Presentation of the Dissertation:

The dissertation materials were presented at the First Regional Scientific-Methodological Conference "Practice of Teaching Ecology in Schools, Colleges, and Universities of the Chita Oblast and the Aginsky Buryat Autonomous Okrug", Chita, 2002; at the XVII World Congress on Asthma, St. Petersburg, 2003; at the All-Russian Scientific-Practical Conference dedicated to the 50th anniversary of the formation of the Chita State Medical Academy "Actual Problems of Clinical and Experimental Medicine", Chita, 2003; at the 13th National Congress on Diseases of the Respiratory Organs, St. Petersburg, 2003; at the 14th National Congress on Diseases of the Respiratory Organs, Moscow, 2004; at the Second All-Russian Conference "Healthy Child", Chita, 2004; at the IX, X Congresses of Pediatricians of Russia, Moscow, 2004, 2005.

Structure and Volume of the Dissertation:

The dissertation consists of an introduction, 3 chapters, conclusion, theses, practical recommendations, appendices, and a bibliography including 134 domestic and 69 foreign sources. The work is presented on 123 pages of typed text, contains 21 tables, 7 figures, appendices. 11