Obstructive Lung Diseases

·         Patients generally have no problems getting air into the lungs, but do have problems getting air out of the lungs

·         There are 4 types of obstructive lung diseases:

                     I.      Chronic Bronchitis

                   II.      Emphysema

                  III.      Bronchiectasis

                IV.      Asthma

1. Chronic Bronchitis

·         Definition: excess secretion of mucus into the bronchial tree occurring on most days for three months in the year, for at least two successive years

o        This diagnosis is based primarily on clinical findings, not pathological findings

o        Note: other lecturers/sources have different durations for diagnosis of chronic bronchitis.  The main point is that this diagnosis requires an extended duration with symptoms.

·         Pathological findings:

o        Mucus gland hypertrophy within the tracheobronchial tree

o        Constant production of sputum

o        Inflammation within the respiratory system (i.e., increased lymphocytes, eosinophils, PMNs)

§         Also see hyperemia, mucoid plugs within bronchi

o        No relationship exists between extent of mucus gland hypertrophy and extent of inflammation.  So the disease is treated based on clinical findings, not pathological findings

o        Presence of Curschmann’s spirals: mucus plug that blocks bronchioles; indicative of obstructive lung disease

2. Emphysema

Definition: abnormal dilation of any part of the acinus, accompanied by destruction of respiratory tissue

o        Alveolar destruction leads to decreased oxygen diffusion capacity

·         Following inspiration in a normal patient, expiration involves passive elastic recoil.  In emphysema patients, the destruction of lung tissue leads to reduced elasticity; therefore, the lung does not recoil properly.

·         Typically hear expiratory wheeze in these patients

Two Types of Emphysema:

o        Centrilobular emphysema

§         Smoking-related

§         Most common form of emphysema

§         Initially, respiratory bronchioles are dilated more than alveolar sacs.  Eventually, alveolar sacs become dilated as well as the disease progresses

§         Patchy dilation is seen (i.e., not the entire lung)

§         Bullous emphysema results from extension of the dilation into the pleural space; rupture of these “bullae” can lead to pneumothorax

§         See flattened diaphragm via chest x-ray due to lung dilation

o        Pan-acinar emphysema (a.k.a., panlobular)

§         Seen in patients with a-1 antitrypsin deficiency (patients have unopposed protease activity that results in elastin/collagen destruction); patients will present at a younger age

§         Uniform distribution of dilation and tissue destruction is seen (i.e., the entire lung)

3. Bronchiectasis

·         Definition: abnormal, permanent dilation of bronchi (can include lobes, or parts of lobes)

·         Bronchiectasis occurs after bronchial obstruction (via tumor, foreign body, mucus impaction, asthma), and frequently involves an infectious process in the lungs

o        Another way to look at it: if you have a blockage, infections distal to that blockage accumulate and cannot be coughed up

o        Anaerobic organisms are most frequently involved with bronchiectasis, so the patients have foul-smelling secretions (Dr. Aisner emphasized that this smell is something you never forget)

·         Frequently see hyperemia and inflammatory cells (PMNs) in bronchiectasis

·         Clinical manifestations: recurrent cough with purulent sputum, hemoptysis, and obstructive lung disease

4. Asthma

·         Definition: paroxysmal (sudden, often recurrent) airflow obstruction; airways are hyperresponsive

·         Asthma is the most common disease affecting the respiratory tract, and is especially common in children, and those in urban areas

·         Asthma involves paroxysmal breathlessness and wheezing, which are relieved by bronchodilators

·         Epidemiology: men>women (2:1 ratio); present in 4-5% of US population

·         Precipitating factors of asthma: allergens, heat/cold/exercise, emotional stress, environmental pollutants

·         Pathology findings

o        Lungs are hyperinflated, and rib impressions on lungs can be seen on autopsy

o        Constricted bronchioles filled with obstructive mucus plugs

o        Inflammatory cells (eosinophils & lymphocytes) are present

o        Smooth muscle hypertrophy

o        Epithelial cells are shed into the bronchiolar/alveolar lumen

·         Autonomic nervous system plays a role in bronchiolar smooth muscle constriction

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