Define Stridor in Children. Describe its causes and investigations.

Definition

• Stridor is a harsh, high-pitched noisy sound produced by turbulent airflow through a partially obstructed upper airway (larynx/trachea).
• Its timing helps localise the obstruction and it is always a sign that needs assessment.

Timing & Localisation

• Inspiratory stridor → obstruction above/at the larynx (extrathoracic).
• Expiratory stridor / wheeze → intrathoracic (lower trachea/bronchi).
• Biphasic stridor → a fixed obstruction (e.g. Subglottic stenosis).

Acute Causes

• Croup (commonest — barking cough, stridor, hoarse voice).
• Acute epiglottitis (toxic, drooling, no cough — an emergency).
• Foreign body (sudden choking); bacterial tracheitis; retropharyngeal abscess; anaphylaxis/angio-oedema.

Chronic / Congenital Causes

• Laryngomalacia — the commonest cause of chronic stridor in infants.
• Vocal-cord palsy, subglottic stenosis, subglottic haemangioma, and vascular ring.

Laryngomalacia (the Commonest Chronic Cause)

• Inspiratory stridor from birth/early weeks, worse supine, on feeding and crying, and better prone.
• The infant is otherwise well and thriving; it is due to a floppy, immature larynx.
• Usually self-limiting, resolving by 12–18 months; surgery only if severe (feeding difficulty, failure to thrive, apnoea).

Approach

• Assess severity first (stridor at rest, indrawing, cyanosis, feeding) and secure the airway if compromised.
• Identify the cause from the history (onset, fever, cough, choking) and treat accordingly; avoid upsetting a child with severe obstruction.

Red-flag (emergency) Features

• Stridor at rest, severe chest indrawing, cyanosis, drooling or a toxic appearance.
• Rapidly progressive obstruction, exhaustion or altered sensorium — secure the airway urgently.

Investigation

Guided by the likely cause — most acute stridor is diagnosed clinically; flexible laryngoscopy is used to confirm laryngomalacia and other structural causes of chronic stridor.

The phase of stridor localises the level of obstruction.