Cough is one of the five cardinal symptoms of respiratory disease. The intensity of cough is not necessarily indicative of the severity of the causative disease. Cough reflex is activated by stimulation of irritant receptors in the airway.
The act of coughing is a defence mechanism that helps to keep the lower respiratory passages clear. It protects them from the entry of foreign materials and prevents stagnation of secretions within the air passages.
Causes of cough
Cough with expectoration usually suggests involvement of lungs, bronchial tubes. Dry, unproductive cough is indicative of congestion of throat (pharynx or larynx) or early disease of lung tissue.
The main cough triggers are:
- Infection
- Mechanical irritation of respiratory tract- Foreign body, inhalation of irritant gases, smoking, chronic sinusitis
- Non-Respiratory causes – Cardiac diseases, tumours, some gastric problems
- Reflex causes – Irritation of nerves near the diaphragm
- Psychogenic causes
- Drugs – Few drugs produce cough as a side effect. Example ACE inhibitors
- High altitude and changes in air temperature.
Classifications of cough
Cough is a symptom of respiratory disease and is classified as follows:
- Dry and irritable cough – usually heavy on waking up and during early night
- Dry and nocturnal cough – Chronic pharyngitis and enlarged uvula
- Dry and reflex cough – Irritation of diaphragm (Gastric problems)
- Barking cough – Psychiatric problems
- Short and suppressed cough – Pleurisy and Pneumonia
- Paroxysmal cough - Whooping cough and cancer
- Smokers cough – May occur at any time since respiratory inflammation is chronically present due to frequent smoking