Pharmacy Clinic
Cough
Cough; A sudden explosive expiratory maneuver that tends to clear material (sputum) from the airways.

The purpose of coughing
Coughing helps protect the lungs against aspiration.
Differences among several sites from which cough stimuli can originate may result in variations in the sounds and
patterns of coughing.

Laryngeal stimulation produces a choking type of cough without a preceding inspiration.
Inadequate mucociliary clearance mechanisms (as in bronchiectasis or cystic fibrosis) may produce a pattern of
coughing with less violent acceleration of air and a sequence of interrupted expirations without any intervening
inspiration.

Awareness of cough varies considerably;
        A cough can be distressing when it appears suddenly, especially if associated with discomfort due to chest pain,
dyspnea, or copious secretions.

        A cough that develops over decades (eg, in a smoker with mild chronic bronchitis) may be hardly noticeable or
may be considered normal by the patient.

Questions should determine how long cough has been present, whether it began suddenly, if it has changed recently,
what factors influence it (eg, cold air, talking, posture, eating or drinking, time of day), and whether it is associated with
sputum production, chest or retrosternal or throat pain, dyspnea, hoarseness, dizziness, or other symptoms.
The patient should be asked what he thinks causes it; he may say "something in my lungs that needs to be coughed
up" or "something tickling the back of my throat." Patterns of coughing or precipitating factors may be a clue to its
cause; eg, the patient may have noted an association with work or exercise.

A cough induced by postural change may suggest chronic lung abscess, cavitary TB, bronchiectasis, or a pedunculated
tumor,
A cough associated with eating suggests a disturbance of the swallowing mechanism or possibly a tracheoesophageal
fistula.
A cough that appears on exposure to cold air or during exercise may suggest asthma.
A morning cough persisting until sputum is expectorated typifies chronic bronchitis. A cough that is associated with
rhinitis or wheezing or that is seasonal may be an allergic response.

During the interview, an alert physician notes spontaneous coughing, because its sound can yield useful information
(eg, an audible rattle of secretions; the irritable, dry, barking cough associated with acute tracheitis; or the low-pitched,
blowing, bovine cough without an explosive start heard in a patient with a paralyzed recurrent laryngeal nerve).
A patient who does not cough spontaneously should be asked to do so after the chest examination. Waiting until then
is advisable because coughing earlier may dispel secretion sounds or crackles at the bases before they can be detected.
Listening to the patient's lungs over the chest and at his open mouth both before and after the cough is useful
because movement of secretions may alter physical findings dramatically. On the other hand, posttussive crackles may
appear, particularly over tuberculous lesions in the upper lobes.

A major function of the cough reflex is to help clear secretions from the airways, particularly to help expel them
through the larynx.

Sputum production should be discussed during the history; questions about cough and sputum are usually related, but
occasionally someone who denies coughing states that he produces sputum.

Questions can help determine what the sputum looks like and how easily it is expelled. Changes in character (eg, from
clear white mucus to yellowish, green, or brown purulent material) are important indicators of infection.
Blood streaking and frank hemoptysis are important and likely to be noted by the patient. Gritty material in sputum,
characteristic of broncholithiasis, may be less noticeable, and a patient may deny its presence when first asked but may
later notice and report it.

If possible, the patient should expectorate a sputum specimen during the evaluation. Its gross appearance should be
observed.

A microscopic examination of a small drop taken from a thicker portion of the freshly collected sputum (placed on a
glass slide without staining, compressed with a coverslip, and examined on low power) can provide useful information.
The presence of squamous cells suggests that the material came from above the larynx; true sputum expelled from the
airways is characterized by the presence of alveolar macrophages. Wright's stain shows the proportion of eosinophils;
eosinophilia suggests an allergy. Neutrophils predominate more often in purulent sputum, indicating an inflammatory,
usually infectious process. A Gram stain confirms the presence of bacteria and is the first step in their categorization.
Pathophysiology

•        Airway receptors are found in the trachea, main carina, branching points of large airways, and more distal smaller
airways. Also, they are present in the pharnyx. These sites respond to both chemical and mechanical stimuli.
•        More airway receptors are in the external auditory canals, eardrums, paranasal sinuses, pharynx, diaphragm,
pleura, pericardium, and stomach. These are probably mechanical receptors only.

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