Cough
Cough
is an explosive expiration that provides a normal protective mechanism for
clearing the tracheobronchial tree of secretions and foreign material.
When excessive or bothersome, it is also one
of the most common symptoms for which patients seek medical attention.
Mechanism
·
Coughing
may be initiated either voluntarily or reflexively.
·
As
a defensive reflex, it has both afferent and efferent pathways.
·
The
afferent limb includes receptors within the sensory distribution of the
trigeminal, Glossopharyngeal, superior laryngeal, and vagus nerves.
·
The
efferent limb includes the recurrent laryngeal nerve and the spinal nerves.
Etiology
·
Cough
can be initiated by a variety of irritant triggers either from an exogenous
source (smoke, dust, fumes, foreign bodies) or from an endogenous origin (upper
airway secretions, gastric contents.
·
Any
disorder resulting in inflammation, constriction, infiltration, or compression
of airways can be associated with cough.
·
A
neoplasm infiltrating the airway wall - bronchogenic carcinoma.
·
Airway
infiltration with granulomas - tuberculosis.
·
Compression
of airways results from extrinsic masses such as lymph nodes or mediastinal
tumors, or rarely from an aortic aneurysm.
·
Parenchymal
lung disease - pneumonia, and lung abscess.
·
Congestive
heart failure may be associated with cough, probably because of interstitial as
well as peribronchial edema.
Types based on
duration
·
Acute
cough (< 3 weeks) due to upper respiratory infection, pneumonia, pulmonary
embolus, and congestive heart failure
·
Sub-acute
cough (between 3 and 8 weeks) is commonly post-infectious, resulting from
persistent airway inflammation and/or postnasal drip following viral infection.
·
Chronic
cough (>8 weeks) COPD, bronchogenic carcinoma, asthma, and gastro esophageal
reflux.
Treatment
·
Determining
the underlying cause
·
Elimination
of irritants (cigarette smoke, ACE inhibitors)
·
Bronchodilators
for potentially reversible airflow obstruction, inhaled Glucocorticoids for
eosinophilic bronchitis.
·
Chest
physiotherapy and other methods to enhance clearance of secretions in patients
with bronchiectasis.
·
Antihistamine-decongestant
combination,
·
Antitussive
agent, which increases the latency or threshold of the cough center (codeine)-
dry cough.
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