Restrictive and obstructive lung disease

Emphysema

Acinus is defined as cluster of alveoli ventilated by single respiratory bronchiole (distal to terminal bronchiole). There is dilatation of the acinus in emphysema.

Centriacinar emphysema: destruction of respiratory bronchiole elastic tissue, leading to dilatation; typically occurs in the upper lobes, due to smoking. Cigarette smoke is chemotactic to neutrophils, which release elastases. Free radicals generated by cigarette chemicals cause decrease in antioxidants and antielastases, so you have functional alpha-1-antitrypsin deficiency.

Panacinar emphysema: destruction of entire acinar elastic tissue; typically occurs in lower lobes. Associated with genetic (autosomal dominant) alpha-1-antitrypsin deficiency --> overactivity of elastase --> breakdown of elastin, therefore increased compliance and decreased elasticity.

In emphysema, you get early dyspnea and late decrease in PaO2. The late decline is associated with capillary destruction and pulmonary hypertension. You get hyperventilation and associated respiratory alkalosis. "Pink puffers."

Irregular emphysema: scar emphysema. Paraseptal emphysema: subpleural blebs, can rupture to give pneumothorax. Neither of these types of emphysema are associated with obstructive airway disease.

Chronic Bronchitis

Defined as productive cough at least 3 months for two consecutive years. It is associated very strongly with smoking and cystic fibrosis.

Is associated with mucus overproduction. In bronchi, hypertrophy of mucus-secreting glands (increase in Reid index >0.7), and loss of ciliated epithelium (squamous metaplasia).

In terminal bronchioles, there are mucus plugs, goblet cell metaplasia, hypertrophy of mucus-secreting glands, and fibrosis leading to narrowing of lumen.

You tend to see hypoxemia (decreased PaO2) earlier and dyspnea later. "Blue bloater." You see respiratory acidosis rather than alkalosis. The heart is horizontally oriented rather than vertically oriented on X-ray. These changes tend to distinguish chronic bronchitis from emphysema.

Bronchiectasis
Permanent dilation of bronchi and bronchioles due to destruction of supporting tissue by chronic necrotizing infections. May be secondary to cystic fibrosis, bronchial obstruction (bronchogenic carcinoma), or primary ciliary dyskinesia (Kartagener syndrome).

Restrictive lung disease

Stiffening of lung. Diffuse interstitial fibrosis. Decreased compliance, increased elasticity. Lower volumes overall, but FEV1/FRC preserved or high. Can be caused by pneumoconioses (coal dust, silicosis, asbestos, berylliosis) or granulomatous disorders (sarcoidosis), other immunological disease (SLE, RA -- Caplan syndrome, system sclerosis, Farmer's lung -- IgG and Type III reaction), drugs (amiodarone, bleomycin, cyclophosphamide, methotrexate), or idiopathic (according to Miyai, 2/3 of the time; Goljan says 15%).

Some kind of injury to alveoli. Adaptive increase of Type II pneumocytes, decrease in Type I pneumocytes. Interstitial fibrosis that limits lung expansion; airflow not impaired, as main site of damage is at level of alveoli, not bronchi/bronchioles. Can lead to "honeycomb" appearance. Can interfere with blood-gas exchange.