Chronic non-obstructive bronchitis: causes and pathogenesis

In the emergence of chronic non-obstructive bronchitis, several factors are important, the main one of which, apparently, is the inhalation of tobacco smoke (active and passive smoking). Constant irritation of the bronchial mucosa with tobacco smoke leads to a reorganization of the secretory apparatus, hypercrinia and increased viscosity of the bronchial secretion, as well as damage to the ciliated epithelium of the mucosa, as a result of which mucociliary transport, purging and protective functions of the bronchi are disrupted, which contributes to the development of chronic inflammation of the mucosa. Thus, smoking tobacco reduces the natural resistance of the mucous membrane and facilitates the pathogenic action of the viral-bacterial infection.

Among patients with chronic non-obstructive bronchitis, approximately 80-90% are active smokers. And the number of cigarettes smoked per day and the total duration of smoking matter. It is believed that the most irritating effect on the mucous membrane is smoking cigarettes, and to a lesser extent - tubes or cigars.

The second most important risk factor for chronic non-obstructive bronchitis is the long-term effect on the bronchial mucosa of volatile substances (pollutants) related to industrial and domestic air pollutants (silicon, cadmium, NO2, SO2, etc.). The implementation of these harmful factors also depends on the duration of the pathogenic effect on the mucosa, i.e. From the length of service or the length of residence in unfavorable conditions.

The third factor contributing to the emergence and maintenance of chronic inflammation of the bronchial mucosa is a viral bacterial infection of the airways: repeated acute tracheobronchitis, acute respiratory infections, pneumonia and other bronchopulmonary infections.

The most common disease is caused by:

• respiratory viruses (respiratory syncytial virus, influenza viruses, adenoviruses, etc.);
• Pneumococcus;
• haemophilus influenzae;
• moraxella;
• mycoplasma;
• chlamydia, and others.

For smokers, the most common association is the hemophilic rod and morocell.

Of particular importance is the viral infection. Repeated exposure of respiratory viruses to the epithelium of the bronchial mucosa results in focal dystrophy and death of ciliated cells. As a result, the sections that do not contain ciliated epithelium (the so-called "bald spots") are formed on the bronchial mucosa. It is in these places that the movement of the bronchial secretion in the direction of the oropharynx is interrupted, the bronchial secret is accumulated and it becomes possible for the adhesion of opportunistic microorganisms (pneumococci, hemophilic rod, moraxella, etc.) to the damaged sections of the mucosa. Thus, a viral infection almost always promotes bacterial superinfection.

Infestation of bronchial mucosa by microorganisms generally having a relatively low virulence leads nevertheless to the formation of a cascade of humoral and cellular factors that initiate and maintain chronic inflammation of the mucosa.

As a result, a diffuse inflammatory process (endobronchitis) is formed in the mucosa of large and medium bronchi. In this case, the thickness of the walls of the bronchi becomes uneven: areas of mucosal hypertrophy alternate with areas of its atrophy. Mucous bronchus is edematous, a moderate amount of mucous, mucopurulent or purulent sputum accumulates in the lumen of the bronchi. In most cases, there is an increase in tracheobronchial and bronchopulmonary lymph nodes. Peribronchial tissue is densified, and in some cases loses airiness.

Changes in the bronchi with simple (non-obstructive) bronchitis differ in the following features:

• primary lesion of large and medium bronchi;
• in most cases, relatively low activity of the inflammatory process in the bronchial mucosa;
• absence of significant bronchial obstruction.

In addition to the listed main exogenous risk factors leading to the formation of chronic endobronchitis (smoking, exposure to volatile pollutants and viral-bacterial infection), the so-called endogenous factors play a role in the emergence of chronic non-obstructive bronchitis, including:

• male;
• age over 40 years;
• diseases of the nasopharynx with a violation of breathing through the nose;
• changes in hemodynamics of the small circle of blood circulation, mainly in the microcirculation system (for example, in chronic heart failure);
• insufficiency of the T-system of immunity and synthesis of IgA;
• hyperreactivity of bronchial mucosa;
• family propensity to bronchopulmonary diseases;
• disturbance of functional activity of alveolar macrophages and neutrophils

The listed "endogenous" risk factors, and possibly some other "biological defects", do not belong to the mandatory (obligate) mechanisms of the emergence of endobronchitis, appear to be important predisposing factors facilitating the pathogenic effect on the bronchial mucosa of tobacco smoke, volatile pollutants and viral-bacterial infection .

The main links of the pathogenesis of chronic non-obstructive bronchitis are:

1. Irritant and damaging effects on the mucosa of bronchial tubes of tobacco smoke, volatile pollutants of domestic or industrial nature, as well as repeated viral-bacterial infections.
2. Hyperplasia of goblet cells of bronchial glands, hyperproduction of bronchial secretion (hypercrinia) and deterioration of the rheological properties of mucus (discrinia).
3. Violation of mucociliary clearance, protective and purifying function of bronchial mucosa.
4. Focal dystrophy and death of ciliated cells with the formation of "bald spots".
5. Colonization of the damaged mucous membrane of the bronchi by microorganisms and initiation of a cascade of cellular and humoral factors of mucosal inflammation.
6. Inflammatory edema and the formation of areas of hypertrophy and atrophy of the mucosa.

[1], [2], [3], [4], [5], [6], [7], [8], [9],