The Epidemiology, Etiology, Clinical Features, and Natural History of Emphysema

The Epidemiology,
Etiology, Clinical
Features, and Natural
History of Emphysema
SamuelV. Kemp, MBBS, MRCP*,Michael I. Polkey, PhD, FRCP,
Pallav L. Shah, MD, FRCP
DEFINITION AND HISTORY OF EMPHYSEMA
The term emphysema derives directly from the
Greek word emphys ema, meaning inflation (from
the verb emphysaein, to inflate, or blow in). It is
defined as abnormal, permanent enlargement of
air spaces distal to the terminal bronchioles,
accompanied by the destruction of their walls and
without obvious fibrosis. This destruction results in
the loss of acinar structure, and a subsequent
reduction in the area available for gas exchange
(Fig. 1). The associated loss of elastic tissue leads
to small airway collapse and the gas trapping that
is often a prominent feature of the disease. Clinically,
emphysemais part of the spectrumof disease
encompassed by the term ‘‘chronic obstructive
pulmonary disease’’ (COPD) that also covers
chronic bronchitis, which is a chronic productive
cough for 3 months during each of 2 consecutive
years (other causes of cough being excluded). The
cardinal feature of both emphysema and bronchitis
is airflow obstruction.
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