71 Paediatric Airway Problems

Airway obstruction in children can be at the level of the nasal or pharyngeal airway causing a low-pitched snoring-like noise—‘stertor’. Laryngotracheal obstruction is more likely to cause a ‘higher-pitched stridor’ although there is some overlap. Stertor is dealt with in Chapters 104 (Stertor and Stridor) and 75 (Paediatric Nasal Obstruction).

71.1 Larynx and Trachea

Laryngotracheal obstruction in a child can progress rapidly with devastating consequences. The narrowest point in the baby’s airway is the cricoid ring. Poiseuille’s law dictates that the fourth power of the radius affects airway resistance, so a small reduction in airway radius can produce a profound increase in resistance in an already very small lumen (2-mm radius in a newborn). As fluid (e.g., air) passes through a narrow point, the pressure at the point of narrowing reduces (Bernoulli’s principle). As air passes through an already narrowed tube, the tube tends to narrow further (Venturi’s effect). This reduced pressure plus increased flow rate causes vibration in the walls of the ‘tube’, in this case, the airway and in the column of air. Streamlined or ‘laminar’ flow becomes disordered and ‘turbulent’. This vibration produces a sound which is recognised as ‘stridor’. Clinical features of airway obstruction include stridor, tachypnoea, poor feeding, sternal recession as the baby works hard to breathe, and in the late stages, tiredness, exhaustion and cyanosis—a truly desperate sign. Stridor is typically inspiratory, but as obstruction progresses, it becomes biphasic. Biphasic stridor needs immediate attention. Aetiology may be congenital or acquired.

71.2 Congenital Causes of Laryngotracheal Obstruction

• Laryngomalacia.

• Laryngeal webs.

• Tracheomalacia.

• Vocal cord palsy.

• Subglottic haemangioma.

• Vascular ring.

• Congenital subglottic stenosis.

71.3 Acquired Causes of Laryngotracheal Obstruction

• Acute laryngotracheobronchitis (ALTB or croup).

• Epiglottitis (now rare as children are vaccinated against Haemophilus influenzae B [Hib]).

• Cysts.

• Subglottic stenosis (usually related to intubation).

• Inhaled foreign body.

• Recurrent respiratory papillomatosis.

71.3.1 Laryngomalacia

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