C h a p t e r 2 3
Disorders of Ventilation and Gas Exchange
581
labeled
blue bloaters,
a reference to cyanosis and fluid
retention associated with right-sided heart failure.
In practice, differentiation between the two types of
COPD is often difficult. This is because persons with
COPD often have some degree of both emphysema and
chronic bronchitis.
The manifestations of COPD are associated with
episodes of moderate to severe respiratory impairment
due to obstruction of airflow, which is greater on expi-
ration than inspiration, resulting in increased work of
breathing but decreased effectiveness. The development
of exertional dyspnea, often described as increased
effort to breathe, heaviness, air hunger, or gasping, can
be insidious. Activities involving significant arm work,
particularly above the shoulders, are usually difficult for
persons with COPD. The breathing becomes increas-
ingly more labored, even at rest; the expiratory phase
of respiration is prolonged; and expiratory wheezes
and crackles can be heard on auscultation. Persons
with severe airflow obstruction may also exhibit use of
the accessory muscles, often sitting in the characteris-
tic “tripod” position in which the arms are braced to
facilitate use of the sternocleidomastoid, scalene, and
intercostal muscles. Pursed-lip breathing enhances air-
flow because it increases the resistance to the outflow
of air and helps to prevent airway collapse by increas-
ing airway pressure. Eventually, persons with COPD are
unable to maintain normal blood gases by increasing
their breathing effort. Hypoxemia, hypercapnia, and
cyanosis develop, reflecting an imbalance between ven-
tilation and perfusion.
Exacerbations, which are characterized by increased
cough, sputum, dyspnea, and fatigue, are increasingly
frequent as the disease progresses.
44,45
They are often
difficult to distinguish from other causes of respira-
tory deterioration, such as pneumonia, congestive heart
failure, pulmonary emboli, and pneumothorax with
radiologic or laboratory tests. Persons with frequent
exacerbations exhibit a faster decline in lung function
and have a lower quality of life, an increased need for
hospitalization, and a higher mortality rate.
Severe hypoxemia, in which arterial PO
2
levels fall
below 55 mm Hg, causes reflex vasoconstriction of
the pulmonary vessels and further impairment of gas
exchange in the lung. It is more common in persons
with the chronic bronchitis form of COPD. Hypoxemia
also stimulates red blood cell production, causing poly-
cythemia. The increase in pulmonary vasoconstriction
and subsequent elevation in pulmonary artery pres-
sure further increase the work of the right ventricle. As
a result, persons with COPD may develop right-sided
heart failure with peripheral edema (i.e., cor pulmo-
nale). However, signs of overt right-sided heart failure
are seen less frequently since the advent of supplemental
oxygen therapy (to be discussed).
Diagnosis andTreatment
The diagnosis of COPD is based on a careful history and
physical examination, pulmonary function studies, chest
radiographs, and laboratory tests.
10,42,44
Airway obstruc-
tion prolongs the expiratory phase of respiration and
A
B
FIGURE 23-10.
Characteristics of normal
chest wall and chest wall in emphysema.The
normal chest wall and its cross-section are
illustrated on the left
(A).
The barrel-shaped
chest of emphysema and its cross-section are
illustrated on the right
(B).
(From Smeltzer
SC, Bare BG. Medical-Surgical Nursing. 10th
ed. Philadelphia, PA: Lippincott Williams &
Wilkins; 2004:572.)
