A cough is a voluntary or involuntary action to clear your airways of mucus. Coughs may be dry or productive and can vary in duration.
- Acute cough lasts for less than three weeks
- Chronic cough lasts longer than eight weeks
- Subacute cough is in between, i.e., between 3 to 8 weeks
As a general rule, a cough that is of a shorter duration is likely to be due to infections, whereas a cough of a more prolonged duration (i.e., more than 8 weeks) is not likely to be due to an infection. There are exceptions, and pulmonary tuberculosis is a typical infection that causes the patient to cough for months. The approach taken by a respiratory doctor in all situations is to do an initial history and physical examination.
Acute Cough
The treatment of an acute cough is directed primarily at decreasing the cough in addition to treating the underlying cause. As mentioned above, most of these are due to infections. Infections are divided into upper respiratory tract infections and lower respiratory tract infections. Upper respiratory tract infections are usually due to viruses, while lower respiratory tract infections can be due to viruses or bacteria.
Symptomatic relief of cough can be provided by cough remedies which only provide temporary relief without altering the disease. Another important difference between upper and lower respiratory tract infections is that lower respiratory tract infections like pneumonia may have life-threatening consequences and are a common cause of death.
Examples of upper respiratory tract infections are colds, acute pharyngitis, acute tonsillitis and acute sinusitis. Examples of lower respiratory tract infections include acute bronchitis and pneumonia. If pneumonia is suspected, the doctor will usually order a chest X-ray as it may give a guide to the severity and etiology. It is also usual for the doctor to prescribe antibiotics once pneumonia is suspected.
Chronic Cough
After a thorough medical history and examination, a patient with a chronic cough should have a chest X-ray. A high-quality digital chest X-ray (done in posteroanterior and left lateral positions) can usually suggest conditions like:
- Lung cancer
- Metastatic cancer (cancer from elsewhere spreading to the lung; Bronchiectasis
- Active pulmonary tuberculosis
- Idiopathic pulmonary fibrosis
- Chronic obstructive pulmonary disease (COPD)
Sometimes, a CT scan of the thorax is done to clarify the chest X-ray abnormality.
If the Chest X-ray is normal, usual causes of chronic cough may be due to:
- Cigarette smoking
- Post nasal drip due to allergic rhinitis
- Asthma
- Gastroesophageal reflux
- Drugs, e.g., ACE inhibitors prescribed for hypertension
The key to resolving a chronic cough is to treat the underlying cause. Treatment may include medications such as antihistamines, corticosteroids, antibiotics or acid blockers as well as switching medication that is currently being taken where cough may be a side effect. The doctor may also suggest lifestyle changes as in the case of patients who smoke.
