Cough - classification, etiology, pathogenesis
Cough is a sudden, forceful expiration of air from the lungs, serving as a protective reflex to clear airways of irritants, secretions, or foreign bodies.
Classification
- 1 By duration
- 2 By character
- 3 By sound
- Barking (croup, laryngeal disease).
- Whooping (pertussis).
- Brassy (tracheal tumors ).
Etiology
Acute cough
- Infections: common cold (viral URTI), acute bronchitis, pneumonia.
- Allergic reactions: inhaled irritants, allergens.
- Aspiration of foreign bodies.
Chronic cough
- Chronic bronchitis (smoking- related).
- Asthma (especially cough- variant asthma).
- Gastroesophageal reflux disease (GERD).
- Postnasal drip syndrome (upper airway cough syndrome).
- Bronchiectasis.
- Tuberculosis.
- Medications: ACE inhibitors.
Specific causes of dry cough
- Viral infections (early stage).
- Interstitial lung disease.
- ACE inhibitor therapy
Specific causes of productive cough
- Chronic bronchitis.
- Pneumonia.
- Bronchiectasis.
- Lung abscess.
Pathogenesis
- 1 Stimulation of cough receptors
Located in:
- Larynx.
- Trachea.
- Large bronchi.
- Ear canal, pleura, diaphragm (less common).
- Afferent impulses via vagus or glossopharyngeal nerves to the cough center in the medulla oblongata.
- Efferent impulses sent to:
- Respiratory muscles (diaphragm, intercostals).
- Glottis and accessory muscles.
- 4 Mechanics of cough
Deep inspiration → glottis closure → increased intrathoracic pressure (via forced expiratory effort against closed glottis) → sudden opening of glottis → explosive release of air → clearance of secretions/ irritants.