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Mechanisms of Cough

By on March 16, 2012 in Diseases, Health, Prevention with 0 Comments


Coughing is a response to irritation of the nerves known as cough receptors found in the upper and lower airways. The cough receptors are particularly concentrated in the throat and the major branching points of the tracks tract. They are also found in the sinuses, ear canals, ear drums, esophagus, abdomen and wall of the heart and lungs.

Mechanisms of Cough

These cough receptors may become irritated by multiple mechanisms, including mechanical means such as pressure, by the irritation caused by chemical contaminants in the air such as ozone or sulfur dioxide IV, or by the inflammatory response causing agents allergies (called allergens) or infections like a cold or other virus. Upon stimulation of these receptors, it sends a message to the cough center in the brain, which in turn sends messages to the chest muscles, diaphragm and abdominal wall to contract. This process starts coughing. Coughing is a reflex that can also be produced or inhibited voluntarily.

The cough is the “watchdog” of the lungs, protecting them from dangerous intruders or internal enemies. Consequently, coughing serves to protect our airways keeping them open so you can breathe. It has good and bad effects: while a cough helps clear the airways of mucus, foreign matter or toxic substances may also spread infection and be uncomfortable. abnormalities or alterations in cough reflex may lead to ineffective cough. This could be caused by damage to the cough center in the brain, as certain medications can cause it or tumors that press on him. Ineffective cough may also be due to neuromuscular disease or injury caused by surgery of the abdomen or chest.
During a cough, deletes the contents of the respiratory tract by several mechanisms. The high airflow in the airways causes them to breathe out foreign material and mucus. Also, during the forced exhalation reduces the size of the airway, thereby compressing the secretions of the smaller airways and within the larger airways where the air flow can exhale foreign matter. Finally, there is a rattle or hiss that occurs during coughing causing a vibration of the airways, which literally shakes the mucus in the airways.


In most people, the cough usually begins suddenly and lasts briefly. It is commonly caused by viral infections of upper respiratory tract, and resolves on its own within 7 to 14 days. Any cough that lasts more than three or four weeks is considered chronic and should be evaluated by a doctor.

The cause of chronic cough can usually be determined by a physician who performed a thorough history and physical examination, paying particular attention to the following areas: nose, mouth, throat, ears, sinuses, neck, chest and heart. The doctor will ask specific questions on the duration and type of cough, any exposure to environmental smoke or personal history of smoking, environmental and occupational exposure, and any history of allergies, asthma, sinusitis or infections of the upper airways.

Certain information may be particularly helpful to the physician in making a specific diagnosis such as:

  • Features of cough: dry, wet, metal, such as seals, hissing, barking, nausea, choking or horn
  • Triggering events: exercise, sleep, cold air, irritants, laughing, crying
  • Appearance: seasonal, going to sleep, sleep, awakening, begins suddenly after eating, present in childhood
  • and mucus production: quantity, color and consistency.

If the doctor witnesses the coughing can also provide evidence of their cause. If the cough may not be reproduced in the office, you might want to record on tape or video cough so the doctor can hear or see.

Causes and Complications

The most common cause of cough that lasts one to two weeks is the common cold. Common causes of chronic cough are postnasal drip, asthma and sinusitis, all of which can be triggered by allergies. Other causes include gastroesophageal reflux, chronic bronchitis, drug reactions, bronchiectasis (bronchial tubes damaged and enlarged), infections, environmental irritants and psychosomatic causes (due to the conscious or unconscious). Among the less common causes include: cystic fibrosis, foreign body, tumors, pneumonia, birth defects, heart disease or immunodeficiency, among others. It is not unusual to have more than one cause for the cough. If you have a chronic cough, be sure to consult your doctor to determine the cause (s) (s).

Depending on the history and physical examination can be performed several diagnostic tests, especially for patients with chronic cough. These may include a chest radiograph, a breast x-ray or CT scan, tuberculosis tests, examinations of skin allergies, lung function tests or provocation, exercise, esophageal pH probe to measure acid reflux, blood tests, bronchoscopy, barium swallow, electrocardiogram (ECG), sweat test and / or sputum examination.

The cough can be quite uncomfortable, causing irritation of the larynx, trachea and bronchi, and insomnia. The cough involves vigorous muscular activity, which generates high pressure within the chest cavity. This high pressure can lead to complications, including muscle damage, broken ribs, temporary loss of urine, and disruption of surgical wounds. Serious complications rarely occur as a collapsed lung. It is important that your doctor accurately diagnose and treat a chronic cough to prevent these complications.


Since cough is a symptom and not a disease, successful therapy depends on the specific therapy of the underlying disorder. For example, cough due to asthma should be treated with anti-asthma. Cough due to sinusitis should be treated with antibiotics and cough due to allergic rhinitis with antihistamines or steroid nasal sprays. Cough caused by gastroesophageal reflux improve with treatment of reflux, and cough induced by drugs (eg, due to ACE inhibitors) is solved by not managing them. Cough due to birth defects may require surgery. Cough due to environmental irritants is best treated by avoiding or eliminating irritants. Sometimes, if no cause can be identified clearly, treat cough with specific drugs can serve as a diagnostic test, if the cough is resolved.

In adults, narcotic cough suppressants are an effective temporary treatment, other prescription medicines for cough can also be effective.

Dextromethorphan, a non-narcotic medication is found in many cough preparations sold without a prescription is also effective. However, suppression of cough in patients with diseases of the airways of the lung may be, however, dangerous because it leaves the airways unprotected. Antihistamines do not suppress the cough, and well-controlled studies found that glycerol expectorant guaiacolato no more effective than a placebo, or sugar water. In children, there are no established guidelines for the use of narcotics, including codeine or dextromethorphan as a cough suppressant.

Most cough preparations sold without prescription are combinations of cough suppressants, expectorants, decongestants and antihistamines. Combinations treat different symptoms, so read labels carefully . The pills without prescription with local anesthetics may help the symptoms of cough. The most important thing is to see your doctor if cough persists for more than two weeks.

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