Respiratory System
Answers
183.The answer is b.(Junqueira, p 357. Kumar, pp 717–721. Kasper,
pp 1547–1550.)The patient suffers from emphysema, in which neutrophils
enter the lung parenchyma and secrete elevated levels of elastase, leading
to the destruction of the bronchiolar and alveolar septal elastic tissue sup-
port. The destruction of the elasticity in emphysema leads to diminished
breath sounds. This is coupled with faint high-pitched rhonchi at the end
of expiration and a hyperresonant percussion note. The rhonchi are adven-
titious (not normally present) sounds that may be high pitched, generally
because of bronchospasm, or low pitched, generally because of the pres-
ence of airway secretions. Emphysema is a disease characterized by
parenchymal tissue destruction and, therefore, is not associated with
adventitious breath sounds. However, because most emphysema is due to
cigarette smoking, there is almost always some degree of chronic bronchi-
tis, and therefore, rhonchi can be auscultated.
There are genetic and environmental causes of emphysema. The envi-
ronmental causes include smoking and air pollution, whereas deficiency in
α1-antitrypsin (antiprotease) activity is the genetic cause of the disease.
The balance between normal elastase-elastin production and protease-
antiprotease activity is altered in emphysema. Persons with a deficiency in
α1-antitrypsin activity lack sufficient antiprotease activity to counteract
neutrophil-derived elastase. When there is an increase in the entry and
activation of neutrophils in the alveolar space, more elastase is released,
and elastic structures are destroyed. In smoking there is an increase in the
number of neutrophils and macrophages in alveoli and increased elastase
activity from neutrophils and macrophages. Those changes are coupled
with a decrease in antielastase activity because of oxidants in cigarette
smoke and antioxidants released from the increased numbers of neu-
trophils. The increased protease activity causes breakdown of the alveolar
walls and dissolution of elastin in the bronchiolar walls. The loss of tether-
ing of the bronchioles to the lung parenchyma leads to their collapse. The
bronchioles, unlike the trachea and bronchi, do notcontain hyaline carti-
lage. A relatively thick layer of smooth muscle is found in the bronchioles,
but the bronchioles are tethered to the lung parenchyma by elastic tissue,
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