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Chronic
Obstructive Pulmonary Disease
David Turner, MD
I.
Introduction
A.
Definitions
1. The term "COPD" is limited
to chronic bronchitis and emphysema, which is a disease state characterized by
the presence of airflow obstruction due to chronic bronchitis or emphysema; the
airflow obstruction is generally progressive, may be accompanied by airway
hyperreactivity, and may be partially reversible.
2. Chronic bronchitis:
presence of chronic productive cough for 3months in each of two successive years
(with other causes of chronic cough eliminated).
3. Emphysema: abnormal
permanent enlargement of the airspaces distal to the terminal bronchioles,
accompanied by the destruction of the alveolar walls and without obvious
fibrosis.
B. Epidemiology
1. 14 million individuals in
the US have COPD (12.5 million with chronic bronchitis, 1.65 million with
emphysema).
2. The prevalence has risen
30% in women in the last 20 years.
3. It is the fourth leading
cause of death in US.
II. Etiology and Physiology
A. Risk Factors
1. Smoking
a. Greatest risk factor for
COPD - accounts for 80-90% of the risk.
b. Number of cigarettes each
day and duration of smoking are both important (duration relatively more
important for risk of lung cancer).
c. Pipe and cigar smokers are
at intermediate risk for COPD (between cigarette smokers and nonsmokers).
d. Passive smoking is
associated with an increased risk of airway hyperreactivity; it is unclear
whether there is also a risk for developing COPD.
2. Airways reactivity -
presence of airways reactivity in patients with COPD may increase the rate of
decline in lung function.
3. Alpha 1 anti-trypsin
deficiency (AAT) deficiency accounts for 1% of cases of COPD.
a. AAT is produced in the
liver and found in lungs. It inhibits neutrophil elastase. Coded on
chromosome14.
b. Threshold protective level
- 35% of normal levels (above 80 mg/dL averts significant lung disease).
c. Patients with severe
deficiency may develop symptoms in late 40s or early 50s. Lung disease is
accelerated by smoking.
d. Patients develop emphysema
with predilection for lung bases.
4. Other: air pollution and
occupational exposure probably play a relatively small role in US today.
B. Pathology of COPD
1. Enlargement of bronchial
mucus glands with increased numbers of Goblet cells. Mononuclear inflammatory
process in bronchioles. Smooth muscle hypertrophy in terminal bronchioles.
2. Three pathologic types of
emphysema
a. Centriacinar: process
begins in the respiratory bronchioles and spreads peripherally. Most common type
of emphysema resulting from cigarette smoking. Tends to involve upper portions
of the lung.
b. Panacinar: the entire
alveolus is involved. Type of emphysema seen in homozygous AAT. Involves lower
regions of lung.
c. Distal Acinar:
preferentially involves distal airway structures, alveolar ducts, and sacs.
Associated with apical bullae and spontaneous pneumothorax.
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