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
- sub-acute cough is in between ie between 3 to 8 weeks
As a general rule, cough that is of shorter duration is likely to be due to infections, whereas cough that is more prolonged duration (ie more than 8 weeks) is not likely to be due to infection. There are exceptions and pulmonary tuberculosis is a typical infection that causes the patient to cough for months. The approach in all situations is to do a initial history and physical examination.
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 or 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 infection is that lower respiratory tract infections like pneumonia are a common cause of death.
Examples of upper respiratory tract infections are colds, acute pharyngitis, acute tonsillitis and acute sinusites. 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 to prescribe antibiotics, once pneumonia is suspected.
The approach to a patient with a chronic cough is to do a chest X-ray after careful medical history taking and examination. A high quality digital chest X-ray (done in PA and left lateral position) can usually suggest conditions like:
- Lung cancer
- Metastatic cancer (cancer from elsewhere spreading to the lung)
- 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, the usual causes of chronic cough are:
- Cigarette smoking
- Post nasal drip due to allergic rhinitis
- Gastroesophageal reflux
- Drugs eg ACE inhibitors prescribed for Hypertension
The treatment of chronic cough is to treat the underlying cause.