580
U N I T 6
Respiratory Function
available for replacement therapy in persons with a
hereditary deficiency of the enzyme.
There are two commonly recognized types of emphy-
sema: centriacinar or centrilobular, and panacinar
(Fig. 23-9). The centriacinar type affects the bronchioles
in the central part of the respiratory lobule, with initial
preservation of the alveolar ducts and sacs.
16
It is the
most common type of emphysema and is seen predomi-
nantly in male smokers. The panacinar type produces
initial involvement of the peripheral alveoli and later
extends to involve the more central bronchioles. This
type of emphysema is more common in persons with
α
1
-antitrypsin deficiency. It also is found in smokers in
association with centriacinar emphysema.
Chronic Bronchitis
Chronic bronchitis represents airway obstruction of the
major and small airways.
15,16
The condition is seen most
commonly in middle-aged men and is associated with
chronic irritation from smoking and recurrent infec-
tions. A clinical diagnosis of chronic bronchitis requires
a history of a chronic productive cough that has per-
sisted for at least 3 consecutive months in at least 2 con-
secutive years.
44
Typically, the cough has been present
for many years, with a gradual increase in acute exacer-
bations that produce frankly purulent sputum.
The earliest feature of chronic bronchitis is hyperse-
cretion of mucus in the large airways, associated with
hypertrophy of the submucosal glands in the trachea
and bronchi.
15,16
Although mucus hypersecretion in the
large airways is the cause of sputum overproduction, the
accompanying changes in the small airways (small bron-
chi and bronchioles) are now thought to be important
in the airway obstruction that develops.
15
Histologically,
these changes include a marked increase in goblet cells
and excess mucus production with plugging of the air-
way lumen, inflammatory infiltration, and fibrosis of the
bronchiolar wall. It is thought that both the submuco-
sal hypertrophy in the larger airways and the increase
in goblet cells in the smaller airways are a protective
reaction against tobacco smoke and other pollutants.
Viral and bacterial infections are common in persons
with chronic bronchitis and are thought to be a result
rather than a cause of the disease. While infections are
not responsible for initiating the disease process, they
are probably important in maintaining it and may be
critical in producing acute exacerbations.
Manifestations
The clinical manifestations of COPD usually have
an insidious onset and persons characteristically seek
medical attention in the fifth or sixth decade of life,
with manifestations of excessive cough, sputum pro-
duction, and shortness of breath.
10,44
The productive
cough usually occurs in the morning and the dys-
pnea becomes more severe as the disease progresses.
Frequent exacerbations of infection and respiratory
insufficiency are common, causing absence from work
and eventual disability. The late stages of COPD are
characterized by recurrent respiratory infections and
chronic respiratory failure. Death usually occurs dur-
ing an exacerbation of illness associated with infection
and respiratory failure.
The mnemonics “pink puffer” and “blue bloater”
have been used to differentiate the clinical manifes-
tations of emphysema and chronic obstructive bron-
chitis.
15
Persons with predominant emphysema are
classically referred to as
pink puffers,
a reference to
the lack of cyanosis, the use of accessory muscles,
and pursed-lip (“puffer”) breathing. With loss of lung
elasticity and hyperinflation of the lungs, the airways
often collapse during expiration because pressure in
surrounding lung tissues exceeds airway pressure. Air
becomes trapped in the alveoli and lungs, producing an
increase in the anteroposterior dimensions of the chest,
the so-called
barrel chest
that is typical of persons with
emphysema (Fig. 23-10). Such persons have a dra-
matic decrease in breath sounds throughout the chest.
Because the diaphragm may be functioning near its
maximum ability, the person is vulnerable to diaphrag-
matic fatigue and acute respiratory failure. Persons with
a clinical syndrome of chronic bronchitis are classically
Normal
Centriacinar
Panacinar
Respiratory bronchiole
Terminal bronchiole
Alveoli
Respiratory bronchiole
Terminal bronchiole
Alveoli
Respiratory bronchiole
Terminal bronchiole
Alveoli
FIGURE 23-9.
Centriacinar and panacinar emphysema. In
centriacinar emphysema, the destruction is confined to the
terminal (TB) and respiratory bronchioles (RB). In panacinar
emphysema, the peripheral alveoli (A) are also involved.
(Adapted fromWest JB. Pulmonary Pathophysiology:The
Essentials. 7th ed. Philadelphia, PA: Wolters Kluwer Health |
Lippincott Williams &Wilkins; 2008:56.)
