Cough

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A cough, also known as tussis is a sudden, often repetitive, spasmodic contraction of the thoracic cavity, resulting in violent release of air from the lungs, and usually accompanied by a distinctive sound.

Coughing is an action the body takes to get rid of substances that are irritating the breathing passages. A cough is usually initiated to clear a buildup of phlegm in the trachea. Coughing can also be triggered by a bolus of food entering the trachea rather than the esophagus due to a failure of the epiglottis. Frequent or chronic coughing usually indicates the presence of a disease. Provided the patient is a non-smoker and has a normal chest X-ray, the cause of chronic cough in 93% of all patients is due to asthma, heartburn or post-nasal drip. Other causes of chronic cough include chronic bronchitis and medications such as ACE inhibitors. Coughing can happen voluntarily as well as involuntarily.

Physiology

A cough is a protective, primitive reflex in healthy individuals. The cough reflex is initiated by stimulation of two different classes of afferent nerves, namely the myelinated rapidly adapting receptors, and nonmyelinated C-fibers with endings in the lungs. However it is not certain that the stimulation of nonmyelinated C-fibers leads to cough with a reflex as it's meant in physiology (with its own five components): this stimulation may cause mast cells degranulation (through an asso-assonic reflex) and oedema which may work as a stimulus for rapidly adapting receptors.

Cause

"Persistent cough can be debilitating, socially distressing, and adversely impair quality of life." One of the more common presentations to a medical practitioner is a dry cough. The common causes of chronic dry coughing include post-nasal drip, gastroesophageal reflux disease, asthma, post viral cough and certain drugs such as beta blockers, ACE inhibitors and aspirin. One of the causes of chronic coughing might even be mouth breathing induced dryness in the throat. If a cough lasts for more than three weeks, multiple causes are likely and symptoms will abate only when all the causes are treated will the patient be symptom free. Individuals who smoke often have a smoker's cough, a loud, hacking cough which often results in the expiration of phlegm. In Third World countries, where endemic tuberculosis and HIV related lung disease predominate, structural damage of the airways often occurs with resulting chronic cough.

Coughing may also be used for psychological or social reasons, such as the coughing before giving a speech. This is known as psychogenic, habit or tic coughing, and may increase in frequency in social situations featuring conflict.

Given its irritant nature to mammal tissues, capsaicin is widely used to determine the cough threshold and as a tussive stimulant in clinical research of cough suppressants.

Complications

The complications of coughing can be classified as either acute or chronic. Acute complications include cough syncope (fainting spells due to decreased blood flow to the brain when coughs are prolonged and forceful), insomnia, cough-induced vomiting, rupture of blebs causing spontaneous pneumothorax (although this still remains to be proven), subconjunctival hemorrhage or "red eye", coughing defecation and in women with a prolapsed uterus, cough urination. Chronic complications are common and include abdominal or pelvic hernias, fatigue fractures of lower ribs and costochondritis.

Treatment

Coughs can be treated with cough medicines. Dry coughs are treated with cough suppressants (antitussives) that suppress the body's urge to cough, while productive coughs (coughs that produce phlegm) are treated with expectorants that loosen mucus from the respiratory tract. Centrally acting cough suppressants, such as codeine and dextromethorphan reduce the urge to cough by inhibiting the response of the sensory endings by depolarization, or a dulling, of the vagus nerve, the nerve leading from the brain stem and serving the chest area. A recent study indicates that, because of the presence of theobromine in chocolate, 50 grams of dark chocolate may be an effective treatment for a persistent cough.

Research has demonstrated that gargling with a mixture of warm water and salt washes away the layer of mucus on the throat containing bacteria and proteins that cause inflammation, according to the American Academy of Otolaryngology.

During injections

Coughing during an injection can lessen the pain of the needle stick caused by a sudden, temporary rise in pressure in the chest and spinal canal, inhibiting the pain-conducting structures of the spinal cord.

Sociological aspects

Coughing is not always involuntary, and can be used purposely for social reasons. Clearing the throat or coughing can be used to attract attention, release internal psychological tension or even to be ambiguously provocative--since it cannot always be deciphered what the motivation of the cough was by the listener.

See also

• Pertussis
• Kennel cough
• Cough medicine

References

• McCool F (2006). "Global physiology and pathophysiology of cough: ACCP evidence-based clinical practice guidelines.". Chest 129 (1 Suppl): 48S-53S. PMID 16428691. Full text

External links

• Children's Cough Resource
• FamilyDoctor.org – Chronic cough: causes and cures

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Last updated on Thursday March 13, 2008 at 02:41:59 PDT (GMT -0700)
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