Coughing often occurs under conditions
of good health to remove the mucus and foreign material that have
accumulated in the upper air passages. Thus normal coughing
supplements the action of the cilia (the "built-in-broom") of the air
Coughing occurs when there is an
irritation of the lining of the trachea, or bronchial tubes (air
passages in the lungs), as from bleeding, infection, or inhaled
foreign material. It can also occur when there is pressure or
tugging on the trachea or related organs and irritation of the pleura
(the membrane lining the cavities in which the lungs are situated).
Lastly, coughing can occurs when there is stagnation of blood within
the lungs with seepage of fluids into the air spaces. Coughing
in connection with choking occurs when fluid, food, or some foreign
object finds its way into the air passages. It occurs when there
is local irritation from inhalation of smoke or irritating gases.
This explains the cigarette smoker's cough. Coughing also occurs
when there is local inflammation (usually with infection) of the air
passages as in laryngitis, tracheitis and bronchitis. It
accompanies the common cold, influenza and asthma.
Coughing is usually a prominent symptom
of diseases involving the lungs, including pneumonia, pulmonary
tuberculosis, emphysema, bronchiectasis, fungal infections of the
lung, parasitic diseases of the lung and lung abscess. Cough
also occurs in cancer of the lung, of the pleura, or of the
mediastinum. Bronchiogenic carcinoma (the kind of lung cancer
associated with cigarette smoking) usually becomes well-established
before it produces symptoms. Among its important early symptoms,
when they do occur, are cough and the spitting of blood. Heart
failure can cause coughing. When the left side of the heart
becomes unable to propel the blood at its normal rate and pressure,
the blood tends to stagnate in the lung tissues. The fluid
portion of the blood then seeps into the tiny air spaces of the lungs
and interferes with the normal exchange of oxygen and carbon dioxide.
Coughing then occurs as a means of clearing out the air spaces.
Sometimes an aneurysm of the thoracic aorta (enlargement of the body's
largest artery) causes coughing by producing pressure against the