Define Bronchial Asthma in Children. Describe its aetiology, pathophysiology, clinical features and investigations.

Definition

• Bronchial asthma is a chronic inflammatory disorder of the airways characterised by reversible airflow obstruction, bronchial hyper-responsiveness and recurrent episodes of wheeze, cough, breathlessness and chest tightness.
• It is the commonest chronic respiratory disease of childhood.

Etiology & Triggers

• Host factors — genetic predisposition and atopy (personal/family history of eczema, allergic rhinitis).
• Viral respiratory infections — the commonest trigger of exacerbations in children (rhinovirus, RSV).
• Allergens — house-dust mite, pollen, moulds, pet danders, cockroach.
• Irritants & others — tobacco/biomass smoke, air pollution, cold air, exercise, strong emotions and certain drugs (aspirin, NSAIDs).

Pathophysiology

Trigger + atopic (Th2) inflammation → Mast cells, eosinophils, IgE activated → Bronchoconstriction + mucosal oedema + mucus plugging → Airflow obstruction (reversible) → Chronic inflammation → airway remodelling (fixed component)

The early phase (bronchoconstriction) is mediated by histamine and leukotrienes; the late phase (inflammation, oedema) occurs hours later. Persistent inflammation causes airway hyper-responsiveness and, over time, remodelling.

Clinical Features

• Recurrent, episodic wheeze, cough (often nocturnal/early-morning), breathlessness and chest tightness.
• Symptoms show diurnal variation (worse at night) and are triggered by the above factors.
• History of atopy (eczema, allergic rhinitis) in the child or family.
• Examination in an attack — tachypnoea, prolonged expiration, polyphonic wheeze, use of accessory muscles, hyperinflated chest.

Diagnosis & Investigations

• Largely a clinical diagnosis based on the recurrent, reversible pattern of symptoms.
• Spirometry (age > 5 yr) — an obstructive pattern (↓ FEV1/FVC) with reversibility (FEV1 improves ≥ 12% after a bronchodilator).
• Peak Expiratory Flow Rate (PEFR) — diurnal variability > 13% supports asthma and helps monitoring.
• Supportive — chest X-ray (to exclude other causes; may show hyperinflation), allergy testing, and a therapeutic trial of inhaled steroids.

Assessment of Acute Severity

Management of Acute Exacerbation

• Oxygen to maintain SpO2 ≥ 94%.
• Inhaled SABA — salbutamol via MDI + spacer (2–6 puffs) or nebuliser, repeated every 20 min in the first hour.
• Add ipratropium bromide nebulisation in moderate–severe attacks.
• Systemic corticosteroids — oral prednisolone 1–2 mg/kg (or IV hydrocortisone) early in all but the mildest attacks.
• IV magnesium sulfate in severe/life-threatening attacks; consider IV salbutamol/aminophylline and ICU care/ventilation if not responding.

Long-term (controller) Management — Stepwise (gina)

• Reliever — inhaled SABA (or low-dose ICS-formoterol) as needed.
• Controller — inhaled corticosteroid (ICS) is the cornerstone; step up to ICS + LABA, then higher-dose ICS.
• Add-on — leukotriene receptor antagonist (montelukast); biologics for severe allergic asthma.
• Step up if poorly controlled, step down once controlled for ~3 months; use the lowest effective dose.

Patient & Family Education

• Correct inhaler technique (MDI + spacer) — check at every visit.
• Trigger avoidance; a written asthma action plan; recognise danger signs.
• Adherence to controller therapy; treat allergic rhinitis; annual influenza vaccine.

Complications

• Acute — status asthmaticus, pneumothorax, respiratory failure.
• Chronic — airway remodelling with fixed obstruction, growth & school impact, and steroid side-effects.

Differential Diagnosis of Recurrent Wheeze

• Bronchiolitis (first episode in an infant, viral), foreign body (sudden onset, unilateral).
• Gastro-oesophageal reflux; recurrent aspiration; tuberculosis; suppurative lung disease.
• Cystic fibrosis (with failure to thrive/steatorrhoea); congenital heart disease; structural airway anomaly (vascular ring).

Assessment of Control (gina)

• In the past 4 weeks — daytime symptoms > twice/week, any night waking, reliever use > twice/week, or any activity limitation.
• None → well-controlled; 1–2 → partly controlled; 3–4 → uncontrolled.
• Control guides stepping up or down of therapy at each review.

Special Patterns

• Exercise-induced asthma — wheeze/cough during or after exertion; pre-treat with a SABA and ensure good baseline control.
• Cough-variant asthma — persistent dry cough (often nocturnal) as the only symptom.