What is included in the group of obstructive diseases
The collective group of chronic obstructive pulmonary diseases traditionally includes five pathologies:
- Chronic obstructive bronchitis;
- Bronchiectasis;
- Chronic obstructive pulmonary emphysema;
- Chronic bronchiolitis;
- Bronchial asthma.
The main characteristic of the entire group is a decrease in airway patency and an increase in resistive (non-elastic) resistance to airflow. At the core is an impairment of bronchial drainage function, when an obstruction arises (from the Latin obstructio — hindrance). Partial or complete obstruction can be localized at any level of the respiratory tract: from the trachea to the smallest respiratory bronchioles.
Physiology of resistance and lung volumes
Normally, 80–85% of airflow resistance is created by the upper respiratory tract, with half of this load falling on the nose. Upper airway obstruction can occur for many reasons: due to rhinitis, tumor growth, tongue drop (in a coma, anesthesia, or during sleep), aspiration of fluid and foreign bodies. The lumen can also be blocked by thick sputum, thickened mucous membrane, edema, or laryngeal spasm (against the background of hysteria or inhalation of irritating gases).
In chronic obstruction, the load on the respiratory muscles increases sharply, leading to rapid muscle fatigue. Vital capacity (VC) — the maximum exhale volume after a maximum inhale — is usually reduced. And the standard tidal volume (inhale volume during quiet breathing) shifts toward the inspiratory reserve volume.
Morphology and forms of chronic bronchitis
The morphological substrate is chronic inflammation of the bronchial wall. The key process is hyperplasia of goblet cells and mucous glands, which begin to produce an excessive amount of secretion. Clinically, this manifests as constant sputum production.
Chronic bronchitis is divided into simple and obstructive forms. In the obstructive variant, inflammation captures the peripheral sections (chronic bronchiolitis develops). According to prevalence, diffuse and local bronchitis are distinguished. The local form most often affects the right lung, specifically the bronchi of the 2nd, 4th, 8th, 9th, and 10th segments.
Relationship between bronchitis and emphysema
Chronic bronchitis and emphysema have clear anatomical and diagnostic differences. Bronchitis is distinguished on the basis of clinical features and affects the entire bronchial tree. Emphysema is determined by morphological changes, and its localization is strictly limited to the acinus.
These pathologies can exist in isolation (for example, pure emphysema in hereditary $\alpha_1$-antitrypsin deficiency). However, in practice, they almost always coexist. The process of their formation consists of the interaction of risk factors and cellular-molecular mechanisms. That is why clinicians combine them into a single nosology — COPD.
Briefly: answers to topical questions
What microscopic changes in the bronchial wall are characteristic of chronic bronchitis?
Microscopic changes in the bronchial wall in chronic bronchitis are associated with the development of chronic mucous or purulent catarrhal inflammation.
The following abnormalities are distinguished:
- Epithelial changes — metaplasia of the covering epithelium, hyperplasia of goblet cells and bronchial mucous glands.
- Structural changes — pronounced inflammatory infiltration, proliferation of granulation tissue with the possible formation of inflammatory mucosal polyps, as well as sclerosis and atrophy of the muscular layer.
What macroscopic lung changes are characteristic of chronic obstructive emphysema?
Macroscopically, in chronic obstructive emphysema, the lungs are significantly increased in size and cover the anterior mediastinum with their edges.
The following signs are characteristic:
- Condition of the tissue — the lung tissue becomes bloated, pale, and soft.
- Behavior during autopsy — the lungs do not collapse when the chest is opened.
- Sound phenomena — a characteristic crunch is heard when the tissue is cut.
- Changes in the bronchi — mucopurulent exudate is released from the bronchial lumens when pressed.
What morphological types of pulmonary emphysema are distinguished depending on acinar involvement?
Depending on the involvement of the acinus, the following morphological types of emphysema are distinguished in sources:
- Panacinar emphysema — both central and peripheral parts of the acinus are involved, i.e., the entire acinus suffers.
- Paraseptal emphysema — only the distal part of the acinus is altered, while the proximal part remains unchanged.
- Centriacinar emphysema — distinguished as a separate type in the classification according to the acinar lesion zone.
- Irregular emphysema — characterized by uneven involvement of the acinus.
What pulmonary and extrapulmonary complications are most characteristic of COPD?
Chronic obstructive pulmonary disease is characterized by a progressive course with the development of severe pulmonary and cardiovascular complications.
The main complications include:
- Respiratory failure — progressive impairment of pulmonary ventilation and gas exchange.
- Hemodynamic disorders — pulmonary arterial hypertension and right ventricular hypertrophy.
- Cardiac pathology — development of cor pulmonale (cor pulmonale) and progressive cardiopulmonary failure.
- Bulla complications — in the presence of bullous emphysema, pneumothorax, bleeding from the bulla, and its infection are possible.
To avoid confusing COPD and asthma, remember a simple rule: COPD is a Chronic and Irreversible obstruction, and Asthma is an Attack with Reversible spasm.
Class and exam questions
What is the main difference between COPD and bronchial asthma?
In COPD, airway obstruction is primary and irreversible. For bronchial asthma, in contrast, reversible obstruction is typical.
What genetic factors contribute to the development of COPD?
The disease can develop against the background of hereditary pathologies. Classic examples are cystic fibrosis and immotile cilia syndrome (Kartagener syndrome).
What is the epidemiological picture of the disease?
This is the most common chronic lung disease, affecting about 20% of men. There is an increase in incidence among women due to tobacco smoking, and mortality in the Russian Federation is comparable to mortality from lung cancer.
What else to study on this topic
- Cellular and molecular mechanisms of COPD morphogenesis
- Isolated emphysema in alpha-1 antitrypsin deficiency
- The role of respiratory viral infections in the etiology of the disease
- Pathophysiology of respiratory muscle fatigue in obstruction
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