Biomedical Engineering Reference
In-Depth Information
5
Airway Mucus Secretion
Duncan F. Rogers
National Heart and Lung Institute, Imperial College London, London, U.K.
I.
INTRODUCTION
Airway mucus hypersecretion was long dismissed as a benign, albeit aggra-
vating, component of chronic obstructive pulmonary disease (COPD) (1,2).
This doctrine is exemplified in omission of the term 'mucus hypersecretion'
from recent definitions of COPD (3). However, new epidemiological studies
(4) demonstrate that mucus is far from innocent. In fact, airway mucus
hypersecretion is now recognized as a potential risk factor for an accelerated
loss of lung function in COPD. Thus, current wisdom declares that mucus
hypersecretion is a key pathophysiological feature in many patients (Fig.1).
Mucus hypersecretion, implicit in the term chronic bronchitis, is one of
three pathophysiological entities that comprise COPD, the other two being
chronic bronchiolitis (small airways disease), and emphysema (alveolar
destruction with airspace enlargement). The relative contribution of each
component to pathophysiology varies between patients, with the impact
of mucus hypersecretion on clinical symptoms varying accordingly. In many
patients, hypersecretion has clinical significance, for example in patients
with low lung function or who are prone to chest infections (5) (Fig. 2). Con-
sequently, it is important to understand the pathophysiology of mucus
hypersecretion in COPD. This in turn should allow identification of thera-
peutic targets and rational development of pharmacotherapeutic drugs.
The present chapter: 1) assesses the contribution of airway mucus hyper-
secretion and impaired mucociliary clearance to pathophysiology of the
'bronchitic' component of COPD, 2) considers the epidemiology and
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