Pain
and Lung Disease
Lung tissue and the visceral pleura are devoid of
pain-sensitive nerve endings, so that pain in the chest is always the result of
conditions affecting the surrounding structures. In tuberculosis or pneumonia,
for example, pain may never be experienced. Once lung disease crosses the
visceral pleura and the pleural cavity to involve the parietal pleura, pain
becomes a prominent feature. Lobar pneumonia with pleurisy, for example,
produces a severe tearing pain, accentuated by inspiring deeply or coughing. Because
the lower part of the costal parietal pleura receives its sensory innervation
from the lower five intercostal nerves, which also innervate the skin of the
anterior abdominal wall, pleurisy in this area commonly produces pain that is
referred to the abdomen. This has sometimes resulted in a mistaken diagnosis of
an acute abdominal lesion.
In a similar manner, pleurisy of the central part of the
diaphragmatic pleura, which receives sensory innervation from the phrenic nerve
(C3, 4, and 5), can lead to referred pain over the shoulder because the skin of
this region is supplied by the supraclavicular nerves (C3 and 4).
Loss
of Lung Elasticity
Many diseases of the lungs, such as emphysema and pulmonary fibrosis,
destroy the elasticity of the lungs, and thus the lungs are unable to recoil
adequately, causing incomplete expiration. The respiratory muscles in these
patients have to assist in expiration, which no longer is a passive phenomenon.
Loss
of Lung Distensibility
Diseases such as silicosis, asbestosis, cancer, and
pneumonia interfere with the process of expanding the lung in inspiration. A
decrease in the compliance of the lungs and the chest wall then occurs, and a
greater effort has to be undertaken by the inspiratory muscles to inflate the
lungs.
No comments:
Post a Comment