Cough

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Definition | Causes | Risk Factors | Symptoms | Diagnosis | Treatment | Prevention | Organizations

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Definition

A cough is a sudden expulsion of air from the lungs. A cough can be voluntary. However, it is usually an involuntary reflex response to stimulation of the cough receptors in the airways. A cough is one of the body's defense mechanisms. Its purpose is usually to clear secretions and inhaled foreign substances from the lungs and respiratory tract.

There are two types of cough:

• Acute cough – lasts for less than 3 weeks
• Chronic cough – lasts for 3 weeks or more

Causes

An acute cough is usually caused by an infection such as a cold or flu. In some cases, an acute cough can be the sign of a more serious condition, such as:

• Pneumonia
• Congestive heart failure
• Pulmonary embolus
• Aspiration of a foreign body

A chronic cough can be caused by many factors. Common examples include:

• Smoking
• Repeated inhalation of environmental irritants, such as:
  • Smoke
  • Dust
  • Fumes
• Postnasal drip from:
  • A cold
  • Sinus problems
  • Allergies
• Asthma
• Gastroesophageal reflux disease (GERD)
• Chronic lung disease, such as:
  • Chronic bronchitis
  • Emphysema
  • Bronchiectasis
  • Interstitial lung disease
• Medications, such as ACE inhibitors for high blood pressure

Risk Factors

A risk factor is something that increases your chances of getting a disease or condition.

The main risk factor for cough is being exposed to irritants, for example:

• Smoke
• Noxious fumes
• Air-born substances, such as:
  • Pollen
  • Dust
  • Pollution

Symptoms

A cough may sometimes be worse upon arising and during the night.

Acute and chronic coughs are symptoms of an underlying condition or disease. Usually, an acute cough does not require medical attention. However, a chronic cough is a sign that you should seek medical care.

More serious symptoms associated with cough that may require prompt medical attention include:

• A cough brings up sputum that is:
  • Bloody
  • Extremely thick
  • Yellowish or greenish in color
• A cough is accompanied by:
  • Chest pain
  • Shortness of breath
  • Wheezing
  • Unintentional weight loss

Diagnosis

The doctor will ask about your symptoms and medical history, and perform a physical exam.

Acute cough is usually diagnosed by its accompanying symptoms.

In the diagnosis and assessment of chronic cough, your doctor will look for symptoms that suggest an underlying cause. Tests may include:

• Chest x-rays
• CT scan of the chest – a type of x-ray that uses a computer to make pictures of the inside of the body, in this case the chest
• Analysis of a sputum sample
• Blood test to check for infection
• Skin tests if allergies are suspected
• Pulmonary function tests (PFTs) – tests to measure lung function
• Bronchoscopy – insertion of a long, thin instrument to collect samples from the airways or lungs for further testing

Treatment

The best treatment for a cough is to treat the condition or disease that is causing the cough. A cough can also be treated with medications that either:

• Make the cough more productive
• Suppress the cough

To make a cough more productive

A wet cough, which is a cough that produces sputum, is an important way for your body to clear secretions from the airways. Wet coughs should not be suppressed, but may need to be made more productive. They may be treated with expectorant medications. These medications help thin bronchial secretions and make them looser and easier to cough up.

Examples of expectorant drugs include:

• Iodide
• Guaifenesin (e.g., Robitussin)

Moisture therapy also helps make secretions looser and easier to cough up. This therapy involves adding moisture to air with a steam vaporizer or cool-mist humidifier.

To suppress a cough

Medications are used to suppress a cough when:

• It is a dry cough (cough that does not produce sputum)
• It is a wet cough that:
  • Causes severe chest pains
  • Interferes with sleep
  • Causes marked discomfort

Examples of cough suppressants include:

• Syrups or lozenges
• Dextromethorphan (e.g., Robitussin Cough Suppressant, Vicks Cough Relief)
• Anesthetic throat sprays
• Narcotics such as codeine

Prevention

To help avoid a cough, do the following:

• Don’t smoke. If you smoke, quit.
• Get treatment for conditions that cause a cough.
• When working in areas where noxious fumes or air-born substances are present:
  • Properly ventilate the area
  • Wear a protective mask or respirator

Organizations

American Academy of Family Physicians
http://www.aafp.org

American Lung Association
http://www.lungusa.org

American College of Chest Physicians
http://www.chestnet.org

SOURCES:

American Academy of Family Physicians

American College of Chest Physicians

The Merck Manual of Medical Information. Simon and Schuster, Inc., 2000.

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Last reviewed June 2002 by Medical Review Board