Definition of bronchitis and its occupational form
Bronchitis is a diffuse inflammation of the bronchi of a non-allergic nature, the pathogenesis of which is based on bronchial obstruction. Occupational bronchitis is a specific variant of somatic bronchitis developing under the influence of occupational factors—toxic and irritant aerosols.
It is fundamentally important to understand the mechanism of ventilation impairment:
- Obstruction is difficulty in exhalation due to the rigidity of the bronchi and bronchioles, which lose their elastic recoil capacity.
- Restriction is difficulty in inhalation associated with a decrease in the compliance of the lung tissue.
Clinically, bronchitis is accompanied by sputum production of a dyscrinism type—both hypercrinia (excessive discharge) and hypocrinism (scanty viscous discharge). The disease tends to progress: acute bronchitis, if the etiological factor persists, naturally transitions into a chronic form.
COPD: key features and differences from bronchitis
Chronic obstructive pulmonary disease (COPD) and its occupational variant (OCOPD) are nosologies in which obstruction is also the leading link in pathogenesis. However, there are two fundamental differences from chronic bronchitis:
- Irreversibility of bronchial obstruction—the bronchial walls undergo persistent fibrotic changes and are incapable of relaxation.
- Etiological incurability—elimination of the causative factor no longer leads to regression of the disease; therapy is aimed exclusively at improving the quality of life.
A common misconception is to consider bronchitis and emphysema as specific cases of COPD. In reality, they are successive links of a single pathological process separated by a temporal and morphological boundary.
Pathogenetic sequence: from bronchitis to emphysema
The development of obstructive pulmonary pathology is a four-stage continuum:
- Acute bronchitis — inflammation of the bronchi under the influence of irritants.
- Chronic bronchitis — the result of failure to eliminate the etiological factor and ineffective therapy.
- COPD — the formation of persistent irreversible obstruction with bronchiolar fibrostenosis.
- Pulmonary emphysema — stretching of the terminal sections of the tracheobronchial tree.
Emphysema develops via a valve mechanism: rigid bronchi allow air in during inspiration, but prevent its exit during expiration. Air accumulates in the acini, leading to overdistension of the alveoli and destruction of the interalveolar septa.
Functional diagnostics and criteria
The key instrumental method for confirming COPD is spirometry with assessment of the forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC). During peak flowmetry, the patient cannot exhale with due force due to fixed obstruction.
Diagnostic criterion for COPD according to GOLD:
- Post-bronchodilator ratio of FEV1/FVC less than 70%, which indicates the retention of a significant volume of air in the lungs.
- Decrease in the partial pressure of oxygen in arterial blood due to impaired gas exchange.
- Development of hypoxia and spasm of the pulmonary arteries—clinically manifested by suffocation.
Body plethysmography is used for an in-depth assessment of lung volumes and the detection of "air trapping".
Clinical presentation and complications
Typical clinical manifestations of obstructive pathology:
- Progressive expiratory dyspnea and episodes of suffocation.
- Cough with sputum production, often purulent during exacerbation.
- Wheezing — a whistling exhalation detected by auscultation and often audible at a distance.
Main complications of COPD:
- Respiratory failure — the inevitable outcome of progressive obstruction.
- Cor pulmonale — dilation and hypertrophy of the right heart chambers due to pulmonary hypertension in the pulmonary circulation, progressing to right ventricular heart failure.
- Infectious complications — suppression of mucociliary clearance and the protective function of the bronchi paves the way for respiratory pathogens; tuberculosis may also develop.
- Pulmonary emphysema as the morphological outcome of prolonged bronchial obstruction.
Key points
- Bronchitis is a diffuse non-allergic inflammation of the bronchi with an obstructive mechanism and sputum production.
- Obstruction impairs exhalation, restriction impairs inhalation; in COPD, the obstructive pattern is dominant.
- The main differences between COPD and chronic bronchitis are the irreversibility of obstruction and etiological incurability.
- Pathological continuum: acute bronchitis → chronic bronchitis → COPD → pulmonary emphysema.
- Emphysema develops via a valve mechanism with air trapping in the terminal sections of the TBT.
- Diagnostic criterion for COPD according to GOLD is FEV1/FVC less than 70% after a bronchodilator.
- Main complications include respiratory failure, cor pulmonale, infections, and emphysema.
- Clinical triad: expiratory dyspnea, productive cough, and wheezing.