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Saturday, August 23, 2025

Cough


Introduction

Cough is a sudden, forceful expulsion of air from the lungs through the glottis, usually accompanied by a characteristic sound. It is a vital airway defense mechanism, but when prolonged or severe, it can significantly impair quality of life.

Cough is categorized as:

  • Acute: <3 weeks (common cold, acute bronchitis, pneumonia).

  • Subacute: 3–8 weeks (post-infectious cough).

  • Chronic: >8 weeks (asthma, GERD, chronic bronchitis, lung cancer).

Mechanism of Cough Reflex

  • Triggered by irritation of receptors in pharynx, larynx, trachea, bronchi, or pleura.

  • Impulses travel via vagus nerve → medullary cough center → respiratory muscles.

  • Sudden expiration occurs against closed glottis → expulsion of air/mucus.

Causes of Cough

1. Respiratory Infections

  • Viral URTI (common cold, influenza).

  • Acute bronchitis.

  • Pneumonia.

  • Tuberculosis.

  • Pertussis (“whooping cough”).

2. Chronic Respiratory Disease

  • Asthma (wheeze, nocturnal cough).

  • COPD/chronic bronchitis.

  • Bronchiectasis.

  • Interstitial lung disease.

3. Malignancy

  • Lung cancer.

  • Endobronchial tumors.

4. Cardiovascular Causes

  • Left heart failure → pulmonary congestion.

  • Pulmonary embolism.

  • Mitral stenosis.

5. Gastrointestinal Causes

  • Gastroesophageal reflux disease (GERD) → reflux cough.

6. Medication-Induced

  • ACE inhibitors (enalapril, lisinopril): Dry, persistent cough.

  • Beta-blockers in asthmatics.

7. Environmental/Irritant

  • Smoking.

  • Air pollution, dust, chemical exposure.

  • Occupational inhalants.

8. Neurological & Psychogenic

  • Habit cough, especially in children.

  • Neurogenic cough (vagal neuropathy).

Clinical Features

  • Productive (wet) cough: Produces sputum; common in infection, bronchiectasis, COPD.

  • Non-productive (dry) cough: Irritative; asthma, GERD, viral illness, ACE inhibitors.

  • Hemoptysis (blood in sputum): TB, cancer, pulmonary embolism, bronchiectasis.

  • Nocturnal cough: Asthma, GERD, heart failure.

  • Cough with wheeze: Asthma, COPD.

  • Cough with weight loss, night sweats: Tuberculosis, cancer.

Diagnostic Approach

1. History

  • Duration (acute, subacute, chronic).

  • Character (dry vs productive).

  • Associated symptoms (fever, dyspnea, chest pain, reflux, wheeze).

  • Medication history (ACE inhibitors).

  • Smoking and occupational exposure.

2. Examination

  • Respiratory: wheezes, crackles, bronchial breathing.

  • Cardiac: murmurs, signs of failure.

  • ENT: postnasal drip, sinusitis.

  • GI: reflux symptoms.

3. Investigations

  • Chest X-ray: Pneumonia, cancer, TB.

  • Sputum analysis: Culture, AFB for TB, cytology.

  • Spirometry: Asthma, COPD.

  • CT chest: Chronic cough, malignancy, interstitial disease.

  • Bronchoscopy: Endobronchial lesions, persistent unexplained cough.

  • pH monitoring / endoscopy: GERD-related cough.

Management and Treatment

A. General Principles

  • Treat underlying cause.

  • Relieve symptoms (especially if disturbing sleep or quality of life).

  • Avoid smoking, irritants.

B. Pharmacological Treatment

1. Antitussives (for dry, non-productive cough)

  • Dextromethorphan: 10–20 mg orally every 4 h or 30 mg every 6–8 h.

  • Codeine: 10–20 mg orally every 4–6 h (use short-term, risk of dependence).

  • Pholcodine: 10–15 mg orally every 4–6 h.

2. Expectorants (to loosen sputum in productive cough)

  • Guaifenesin: 200–400 mg orally every 4 h as needed (max 2.4 g/day).

3. Mucolytics (chronic bronchitis, COPD)

  • Acetylcysteine: 200 mg orally three times daily.

  • Carbocisteine: 750 mg orally three times daily.

4. Bronchodilators (if asthma/COPD-related)

  • Salbutamol inhaler/nebulizer: 100–200 mcg inhaled every 4–6 h PRN.

  • Ipratropium bromide inhaler: 20 mcg 2 puffs every 6 h.

5. Corticosteroids (inflammatory cough)

  • Asthma/COPD: Inhaled budesonide 200–400 mcg twice daily.

  • Acute asthma attack: Prednisone 40–60 mg orally daily × 5–7 days.

6. Antibiotics (only if bacterial infection suspected)

  • Amoxicillin 500 mg orally every 8 h for 5–7 days.

  • Doxycycline 100 mg orally twice daily for 7 days (if atypical pneumonia suspected).

  • Azithromycin 500 mg orally daily × 3 days.

7. GERD-related cough

  • Omeprazole 20–40 mg orally once daily.

  • Lifestyle: elevate head of bed, avoid late meals, caffeine, alcohol.

8. ACE inhibitor-induced cough

  • Stop drug, substitute with ARB (losartan 50 mg orally daily).

C. Non-Pharmacological Treatment

  • Honey (especially in children >1 year).

  • Steam inhalation for soothing effect.

  • Hydration to thin secretions.

  • Smoking cessation.

Complications of Chronic Cough

  • Rib fractures, muscle strain.

  • Sleep disturbance, fatigue.

  • Urinary incontinence (especially in women).

  • Vomiting, syncope in severe cases.

  • Social embarrassment and reduced quality of life.

Prognosis

  • Acute cough: Usually self-limiting (viral URTI, bronchitis).

  • Chronic cough: Prognosis depends on treating the underlying cause. Asthma and GERD respond well to therapy, while COPD and cancer carry more guarded outcomes.

Patient Education

  • Seek medical advice if cough >3 weeks, blood in sputum, weight loss, fever, or breathlessness.

  • Complete full antibiotic courses if prescribed.

  • Asthmatics/COPD patients must adhere to inhaler therapy.

  • Avoid triggers (dust, smoke, allergens).

  • Children with persistent cough should always be assessed to rule out asthma or pertussis.




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