A cough is a sudden expulsion of air from the lungs. 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 three weeks
- Chronic cough–lasts for three weeks or more
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:
- Congestive heart failure
- Pulmonary embolus
- Lung cancer
- Aspiration of a foreign body
A chronic cough can be caused by many factors. Common examples include:
- Chronic bronchitis due to smoking
- “Reflux” of acid from the stomach into the throat
- “Post nasal drip,” which may in turn be due to:
- Repeated inhalation of environmental irritants
- Sinus inflammation
- Bronchiectasis is one of many other less common causes of chronic cough
- Medications, most notably angiotensin converting enzyme (“ACE”) inhibitors, can sometimes cause cough
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:
- Noxious fumes
- Allergens such as pollen and dust
- Smog and other environmental pollutants
Exposure to viral and bacterial infections affecting the respiratory tract also increases the risk of cough. Smoking is a major risk for serious conditions linked to chronic cough including lung cancer and chronic bronchitis.
A cough may sometimes be worse when waking up and during the night while lying down.
Acute and chronic coughs are symptoms of an underlying condition or disease. Many acute coughs do not require medical attention unless they fail to resolve or become progressively worse. A chronic cough, however, is a sign that you should seek medical care.
More serious symptoms that may require prompt medical attention include coughs accompanied by:
- Large amounts of thick sputum
- Chest pain
- High fever and/or chills
- Shortness of breath
- Unintentional weight loss
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 and signs that suggest an underlying cause. Tests may include:
- Chest x-rays–a test that uses radiation to take a picture of structures inside the body, in this case the chest
- CT scan of the chest–a type of x-ray that uses a computer to create images of structures inside 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)–to measure lung volumes and air flow rates
- Bronchoscopy–insertion of a long, thin instrument to view the interior of the airways and collect samples for further testing
The best treatment for a cough is to treat the responsible underlying condition. A cough can also be treated with medications that either:
To make a cough more productive
- Make the cough more productive
- Suppress the cough
A wet cough, which 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.
Guaifenesin is the best known expectorant and is found in a variety of over-the-counter cough and cold products (Robitussin®, for example).
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:
- dry (producing little or no sputum)
- wet, but causes severe chest pain or interferes with sleep
Examples of cough suppressants include:
- Local anesthetics in the form of lozenges, sprays, and pills
- Dextromethorphan (eg, Robitussin® Cough Suppressant, Vicks® Cough Relief)
- Narcotics such as codeine
To help avoid a cough:
- Don’t smoke. If you smoke, quit.
- Treat the underlying condition(s) responsible for the cough.
- When working in areas where noxious fumes or airborn substances are present:
- Be sure the area is properly ventilated
- Wear a protective mask or respirator