Cough

A cough 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 air passages. A cough is usually initiated to clear a buildup of phlegm in the vertebrate trachea|trachea. Coughing can also be triggered by a bolus of food going down the trachea instead of the esophagus due to a failure of the epiglottis, although this may result in choking instead. 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, reflux (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.

Beyond the physiological causes, there can be psychological and social reasons for the act of coughing, as such, known as psychogenic coughing, habit coughing, or tic coughing. An example of this would be seen in an individual who coughs or clears his throat before a public speech as a means to gain attention or as a manifestation of nervousness.

Physiology
Cough is a protective, primitive reflex in healthy individuals. The cough reflex is initiated by stimulation of two different classes of sensory afferent fiber, namely the myelinated rapidly adapting receptors (RAR), and nonmyelinated C-fibers with bronchial or pulmonary endings.

Cause
Persistent cough can be debilitating, socially distressing, and adversely impair quality of life.

One of the common presentations to the medical practitioner is dry cough. The common causes of chronic dry cough include post-nasal drip; gastroesophageal reflux disease; cough variant asthma; drugs, such as beta blockers, ACE inhibitors, aspirin, which should be investigated in people above 40 years; Post viral bronchial hyperresponsiveness; and habitual cough. When cough lasts for more than a few weeks multiple causes are likely and only when all the causes are treated will the patient be symptom free.

Cigarette smokers often have what is referred to as a Smoker's Cough. This takes the form of a loud hacking cough and often results in the expiration of phlegm.

Given its irritant nature to mammal tissues, capsaicin, the active ingredient of chili peppers, is widely used to determine the cough threshold and as tussive stimulants 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 when coughs are prolonged and forceful. Cough syncope is caused by decreased blood flow to the brain, because the intrathoracic pressure is raised due to the coughing. Other acute complications include insomnia, cough-induced vomiting, chest pain due to muscular strain of incessant coughing, rupture of blebs causing spontaneous pneumothorax, and subconjunctival hemorrhage or "red eye". In severe cases, prolonged coughing can cause fatigue fractures of lower ribs and costochondritis, an inflammation of the connective tissue between the breastbone and the ribs. Chronic complications are common. In certain cases, it can even lead to abdominal or pelvic hernias. In women with prolapsed uterus, cough micturition (urination) can result, which can be a major social nuisance. Cough defecation can also occur.

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 of the vagus nerve.

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.

Gargling with salt and warm water can also be very helpful by cutting phlegm.