DISEASES OF RESPIRATORY SYSTEM

There are a lot of diseases of the respiratory system as well as the etiologic factors, which cause these diseases. Acute and chronic bronchitis, pneumonia, destructive processes (abscess and gangrene), chronic non-specific pulmonary diseases and cancer of the lungs are the most common.

ACUTE BRONCHITIS

Acute inflammation of the larger bronchi, which lie outside the lung lobules, is called acute bronchitis and that of the small interlobular bronchi and bronchioles is called acute bronchiolitis. As a rule acute bronchitis develops due to bacterial and virus invasion. Acute bronchitis may be catarrhal, membranous and putrid.

PNEUMONIA

Pneumonia is acute inflammation of the lung parenchyma distal to the terminal bronchioles, which consist of the respiratory bronchiole, alveoles ducts, alveolar sacs and alveoli.

Etiologic classification of pneumonia:

1. Bacterial pneumonia:

a) lobar pneumonia;

b) bronchopneumonia (lobular pneumonia);

2. Viral and mycoplasmal pneumonia;

3. Other types of pneumonias:

a) Pneumocystis carini pneumonia;

b) legionella pneumonia;

c) aspiration pneumonia;

d) hypostatic pneumonia;

e) lipid pneumonia.

According to the anatomic part of the lung parenchyma involved pneumonias are classified into 3 types:

1. Lobar pneumonia;

2. Bronchopneumonia (lobular pneumonia);

3. Interstitial pneumonia.

Lobar pneumonia (crupous) is an acute bacterial infection of a part of a lobe, the entire lobe, or even two lobes of one or both the lungs.

Etiology. More than 90% of this are caused by pneumococcus.

Pathology. There are 4 pathologic phases in the morphogenesis of lobar pneumonia. Stage of congestion (initial phase); red hepatisation (early consolidation); grey hepatisation (late consolidation) and resolution. The term hepatisation refers to liver-like consistency of the affected lobe on cut section. In red hepatisation macroscopically the affected lobe is

red, firm and consolidated. The cut surface of it is airless, red-pink, dry, granular and has liver-like consistency. This stage is often accompanied by serofibrinous pleurisy. In the stage of grey hepatisation macroscopically the lobe is firm and heavy. The cut surface is dry, grey in appearance with liver-like consistency. Fibrinous pleurisy is prominent.

Complications. There are pulmonary and non-pulmonary complications of the lobar pneumonia.

The pulmonary complications:

1. Organization when carnification develops. This is ingrowth of fibroblasts from the alveolar septa resulting in fibrosed, tough, airless leathery lung tissue.

2. Pleural effusion.

3. Empyema.

4. Lung abscess and gangrene. Non-pulmonary complications. Infection in the

lungs may extend into the pericardium and the heart causing purulent pericarditis, bacterial endocarditis and myocarditis. Besides, otitis media, mastoiditis, meningitis, brain abscess may develop.

Bronchopneumonia (lobular pneumonia) is infection of the terminal bronchioles that extends into the surrounding alveoli resulting in patchy consolidation of the lung.

Etiology. Staphylococci, streptococci, pneumo-cocci, Klebsiella pneumoniae, Haemophilus influenzae, etc. cause this kind of pneumonia.

Macroscopically. There are areas of red or grey consolidation in one or more lobes. On cut surface, these patchy consolidated lesions are dry, granular, firm, red or grey in colour, 3 to 4 cm in diameter, slightly elevated over the surface and are often centered around a bronchiole.

Complications: lung abscess, chronic pneumonia, bronchiectasis, sepsis, pleurisy.

Aspiration pneumonia. Aspiration pneumonia results from inhaling different agents into the lungs. These substances include food, gastric contents, infected material from oral cavity, etc.

Hypostatic pneumonia. Hypostatic pneumonia is the term used for the collection of edema fluid and secretions in the dependent parts of the lungs in bedridden patients.

Lung abscess

Lung abscess is a localized area of necrosis of lung tissue with suppuration. There are 2 types of lung abscesses: primary and secondary lung abscess.

Primary lung abscess develops in an otherwise normal lung as a result of aspiration of infected material.

Secondary lung abscess develops as a complication of some other disease of the lung.