Cough is a protective mechanism that assists in removing foreign particles or excess mucus from the respiratory tract. Thus, in a patient of cough, it is necessary to understand the underlying cause of cough and treat it. Trying to suppress cough is usually not the answer in most cases unless it is extremely tiring.
Depending on the duration, cough may be divided as acute cough that lasts for less than 3 weeks, subacute cough that lasts between 3 to 8 weeks, and chronic cough that lasts for more than 8 weeks. Characteristics of cough in certain conditions are described below:
- An acute cough is usually due to a common cold or flu.
- A dry and hacking cough may be associated with nervousness, viral infections, bronchogenic cancer, or early heart failure.
- A subacute cough where a fit of coughing is followed by a whooping sound may be due to whooping cough or pertussis.
- Conditions that result in dripping of nasal secretions into the throat like allergies and nasal infections can result in chronic cough.
- A person with chronic cough and acidity symptoms like heartburn and regurgitation may be suffering from gastroesophageal reflux disease (GERD).
- Chronic cough with increased mucus secretion in smokers may be due to chronic bronchitis.
- Blood-stained cough in smokers which shows a sudden change in character should be investigated for cancer.
- A person taking medications belonging to the class called ACE inhibitors (examples of these drugs include lisinopril, enalapril, and perindopril) may be suffering from chronic cough due to the medications.
- A person with chronic cough and symptoms like swelling of feet should be evaluated for heart failure.
- Persistent cough with hoarseness of voice may suggest cancer of the larynx.
- Coughing at night may indicate asthma or heart failure.
The causes of cough are listed below:
I. Respiratory Causes:
Conditions affecting the upper respiratory tract: These include -
Conditions affecting the lungs: These include -
- Pneumonia: Pneumonia is a lung infection that may be caused by bacteria, viruses or fungi. Symptoms of pneumonia include fever, cough with sputum production, breathlessness and chest discomfort. The sputum is usually discolored and sometimes tinged with blood. The physician can detect abnormal breath sounds on examination with a stethoscope.
- Tuberculosis: Tuberculosis results in chronic cough. It may initially start as a dry cough but later worsens with the production of white sputum. Sputum may be blood-tinged or bloody in later stages. Tuberculosis also produces low-grade fever, especially at night.
- Lung Abscess: An abscess of the lung causes productive cough with foul-smelling and bad-tasting sputum, sometimes accompanied by coughing up of blood. It is usually accompanied by fever.
- Tropical Eosinophilia: Tropical eosinophilia occurs due to filarial infection. It results in persistent cough that worsens at night with wheezing and may resemble asthma. The spleen may be enlarged in tropical eosinophilia. It is detected by a high eosinophil level in the blood.
- Pulmonary Infarction: Pulmonary infarction is a condition where the blood supply to a part of the lung is cut off due to a clot in the blood vessels. The clot usually travels to the lungs from the lower limbs. The patient presents with sudden breathlessness and cough with pink, frothy sputum. The condition is a medical emergency and requires immediate attention.
- Lung Fibrosis: Lung fibrosis occurs due to conditions like inflammation, infection, or exposure to environmental agents like asbestos. The patient usually suffers from dry, cough that is accompanied by worsening breathlessness.
II. Medications: Medications especially angiotensin-converting enzyme inhibitors (ACE inhibitors) like enalapril and lisinopril result in persistent cough. The cough usually goes away on stopping the medication and substituting it with another from a different class of drugs.
III. Conditions Affecting the Heart: Conditions that affect the heart cause a cough that gets worse on lying down. Heart failure results in cough due to accumulation of fluid in the lungs. It is also accompanied by other features like breathlessness especially on lying down, swelling of the feet and easy fatigability.
IV. Conditions Affecting the Digestive Tract: Gastroesophageal reflux disease (GERD), a condition that causes reflux of acid from the stomach into the food pipe, can result in chronic cough. The acid may move upwards into the respiratory tract and stimulates chronic cough. Symptoms of heartburn should be looked for in these patients.
V. Conditions Affecting the Mediastinum: The mediastinum is the central portion of the chest between the lungs. Conditions affecting the mediastinum like enlarged lymph nodes and mediastinal tumors exert pressure on the respiratory tract and may result in dry and persistent cough.
VI. Psychogenic Causes: Cough may be due to psychogenic cough in some cases. A diagnosis of psychogenic cough may be made only when all other causes of cough are ruled out.
VII. Reflex causes wax or foreign body in the ear, subphrenic or liver abscess: Some conditions like wax or foreign body in the ear, or a liver abscess can stimulate a dry and chronic cough. These conditions should be also looked for in a person with no other obvious cause of cough.
Frequently Asked Questions
1. Which doctor should I visit in case I suffer from cough?
You should visit your general physician if you are suffering from cough for a short duration. A more prolonged cough may need the expertise of a pulmonologist.
2. What are the tests used to diagnose the cause of chronic cough?
A chest x-ray is usually requested to diagnose the cause of chronic cough. Other tests that may be necessary depending on the symptoms of the patient include breathing tests to check for lung function, blood tests, sputum studies, other x-rays (such as those of the sinuses), barium swallow and other gastrointestinal tests to check for GERD, a CT scan of the lungs, and bronchoscopy, wherein a tube with a camera is inserted into the bronchi and the lungs are directly studied for any pathology.
3. What are the medications used to treat cough?
Medications used to treat cough belong to two main categories. Cough expectorants are those medications that help to bring out the sputum from the lungs and the bronchial tree. These medications are used in wet cough like those due to pneumonia, bronchitis etc. On the other hand, cough suppressants are medications used to suppress cough that is dry, irritating and disturbing, but non-infectious. It should be remembered that cough is basically a protective mechanism of the body to expel a foreign substance or an infectious agent from the respiratory tract. Thus, suppressing cough may be harmful in some cases and cough suppressants should be used judiciously.