Definition
A cough is a forceful release of air from the lungs that can be heard.
Coughing protects the respiratory system by clearing it of irritants and
secretions.
Description
While people can generally cough voluntarily, a true cough is usually a
reflex triggered when an irritant stimulates one or more of the cough
receptors found at different points in the respiratory system. These
receptors then send a message to the cough center in the brain, which in
turn tells the body to cough. A cough begins with a deep
breath in, at which point the opening between the vocal cords at the
upper part of the larynx (glottis) shuts, trapping the air in the lungs.
As the diaphragm and other muscles involved in breathing press against the
lungs, the glottis suddenly opens, producing an explosive outflow of air
at speeds greater than 100 miles (160 km) per hour.
In normal situations, most people cough once or twice an hour during the
day to clear the airway of irritants. However, when the level of irritants
in the air is high or when the respiratory system becomes infected,
coughing may become frequent and prolonged. It may interfere with
exercise
or
sleep
, and it may also cause distress if accompanied by
dizziness
, chest
pain
, or breathlessness. In the majority of cases, frequent coughing lasts one
to two weeks and tapers off as the irritant or infection subsides. If a
cough lasts more than three weeks it is considered a chronic cough, and
physicians try to determine a cause beyond an acute infection or irritant.
Coughs are generally described as either dry or productive. A dry cough
does not bring up a mixture of mucus, irritants, and other substances from
the lungs (sputum), while a productive cough does. In the case of a
bacterial infection, the sputum brought up in a productive cough may be
greenish, gray, or brown. In the case of an allergy or viral infection it
may be clear or white. In the most serious conditions, the sputum may
contain blood.
Demographics
Formal statistics on coughs are not maintained. Virtually all persons will
experience coughs several times each year throughout their lives.
Causes and symptoms
KEY TERMS
Antitussive
—A drug used to suppress coughing.
Expectorant
—A drug that promotes the discharge of mucus from respiratory
system.
Gastroesophageal reflux
—The backflow of stomach contents into the esophagus.
Glottis
—The opening between the vocal cords at the upper part of the
larynx.
Larynx
—Also known as the voice box, the larynx is the part of the
airway that lies between the pharynx and the trachea. It is composed of
cartilage that contains the apparatus for voice production–the
vocal cords and the muscles and ligaments that move the cords.
Sputum
—The substance that is coughed up from the lungs and spit out
through the mouth. It is usually a mixture of saliva and mucus, but may
contain blood or pus in patients with lung abscess or other diseases of
the lungs.
A physician or other healthcare provider should be called when a cough
does not subside after three or four
days. Individuals such as smokers, who have chronic coughs, should
consult a doctor if the nature of their cough changes or they produce
blood when they cough.
Diagnosis
To determine the cause of a cough, a physician should take an exact
medical history and perform an exam. Information regarding the duration of
the cough, what other symptoms may accompany it, and what environmental
factors may influence it aid the doctor in his or her diagnosis. The
appearance of the sputum also helps determine what type of infection, if
any, may be involved. The doctor may even observe the sputum
microscopically for the presence of bacteria and white blood cells. Chest
x rays
may help indicate the presence and extent of such infections as pneumonia
or tuberculosis. If these actions are not enough to determine the cause of
the cough, a bronchoscopy or laryngoscopy may be ordered. These tests use
slender tubular instruments to inspect the interior of the bronchi and
larynx.
Treatment
Treatment of a cough generally involves addressing the condition causing
it. An acute infection such as pneumonia may require
antibiotics
, an asthma-induced cough may be treated with the use of bronchodilators,
or an antihistamine may be administered in the case of an allergy.
Physicians prefer not to suppress a productive cough, since it aids the
body in clearing respiratory system of infective agents and irritants.
However, cough medicines may be given if the person cannot rest because of
the cough or if the cough is not productive, as is the case with most
coughs associated with colds or flu. The two types of drugs used to treat
coughs are antitussives and
expectorants
.
Antitussives are drugs that suppress a cough. Narcotics—primarily
codeine—are used as antitussives and work by depressing the cough
center in the brain. However, they can cause such side effects as
drowsiness,
nausea
, and
constipation
. Dextromethorphan, the primary ingredient in many over-the-counter cough
remedies, also depresses the brain's cough center but without the
side effects associated with narcotics. Demulcents relieve coughing by
coating irritated passageways.
Expectorants are drugs that thin mucus in order to make it easier to cough
up. Guaifenesin and terpin hydrate are the primary ingredients in most
over-the-counter expectorants. However, some studies have shown that in
acute infections, simply increasing fluid intake has the same thinning
effect as taking expectorants.
Coughs due to bacterial or viral upper respiratory infections may be
effectively treated with botanical and homeopathic therapies. The choice
of remedy will vary and be specific to the type of cough the person has.
Some combination over-the-counter herbal and homeopathic cough formulas
can be very effective for cough relief. Lingering coughs or coughing up
blood should be treated by a trained practitioner.
Many health practitioners advise increasing fluids and breathing in warm,
humidified air as ways of loosening chest congestion. Others recommend hot
tea flavored with honey as a temporary home remedy for coughs caused by
colds or flu. Various
vitamins
, such as vitamin C, or
minerals
, such as zinc, may be helpful in preventing or treating conditions
(including colds and flu) that lead to coughs. Avoiding of mucus-producing
foods can be effective in healing a cough condition. These mucus-producing
foods can vary, based on individual intolerance, but dairy products are a
major mucus-producing food for most people.
Prognosis
Because the majority of coughs are related to the
common cold
or influenza, most will end in seven to 21 days. The outcome of coughs
due to a more serious underlying disease depends on the pathology of that
disease.
Prevention
It is important to identify and treat the underlying disease and origin of
the cough. It is helpful to avoid cigarette smoke and coming in direct
contact with people experiencing cold or flu symptoms. Hands should be
washed frequently during episodes of upper-respiratory illnesses.
Persons with coughs should be sure to maintain balanced and healthy diets.
Parental concerns
Parents of children under the age of five should closely monitor their
children when they have a cough. Parents of children over five years of
age must accept the fact that their children are likely to acquire coughs
and
related illnesses from schoolmates. They should remain vigilant and
consider having their children seen by a physician if the cough does not
resolve after five to seven days.
See also
Common cold
.
Resources
Boat, Thomas F. "Talipes Chronic or Recurrent Respiratory
Symptoms." In
Nelson Textbook of Pediatrics
, 17th ed. Edited by Richard E. Behrman et al., Philadelphia: Saunders,
2003, pp. 1401–44.
Hanley, Michael E., and Carolyn Welsh.
Current Diagnosis & Treatment in Pulmonary Medicine.
New York: McGraw-Hill, 2003.
Weinberger, Steven E.
Principles of Pulmonary Medicine.
Little Rock, AR: Elsevier, 2003.
Weinberger, Steven E., and Eugene Braunwald. "Cough and
Hemoptysis." In
Harrison's Principles of Internal Medicine
, 15th ed. Edited by Eugene Braunwald et al. New York: McGraw-Hill, 2001,
pp. 203–6.
Chow, P. Y., et al. "Chronic cough in children."
Singapore Medical Journal
45, no. 10 (2004): 462–9.
Franco, E., et al. "Pertussis vaccination for adolescents and
adults."
Expert Opinion on Biological Therapy
4, no. 10 (2004): 1669–76.
American Academy of Family Physicians.
11400 Tomahawk Creek Parkway, Leawood, KS 66211–2672. Web site:
http://www.aafp.org/.
American Academy of Pediatrics.
141 Northwest Point Blvd., Elk Grove Village, IL 60007–1098. Web
site: http://www.aap.org/default.htm.
American College of Physicians.
190 N Independence Mall West, Philadelphia, PA 19106–1572. Web
site: http://www.acponline.org/.
American Lung Association.
1740 Broadway, New York, NY 10019. Web site:
http://www.lungusa.org.
"Cough."
Brigham Young University
, October 26, 2000. Available online at
http://www.byu.edu/shc/library/common/cough.html (accessed
January 5, 2005).
"Cough."
MedlinePlus.
Available online at
http://www.nlm.nih.gov/medlineplus/cough.html (accessed January
5, 2005).
Holmes, Robert L., and Clare T. Fadden. "Evaluation of the Patient
with Chronic Cough."
American Academy of Family Practice
, May 1, 2004. Available online at
http://www.aafp.org/afp/971001ap/cough.html (accessed January 5,
2005).
