Endotracheal intubation and emergency airway equipment — formative SAQs

SAQ 1 — Indication, sizing and the seven-step procedure (15 marks, 15 minutes)

A four-year-old with bacterial tracheitis is brought to the emergency department drooling, sitting forward, retracting hard, and now becoming drowsy. The saturation is falling despite high-flow oxygen. ^{[9] [11]}

Question. Give the indication for a definitive airway here, then calculate the uncuffed and cuffed endotracheal tube internal diameter and the depth at the lips for this child, state the correct blade, and outline the seven-step intubation procedure. Explain your reasoning.

Model answer

Indication (3 marks). The child has a failing airway with impending loss of protection: he is drooling and tiring, his conscious state is dropping, and his oxygenation is failing despite high-flow oxygen. A Glasgow Coma Scale of 8 or less, respiratory failure, severe shock and cardiac arrest are the indications; this child meets the first two. Intubate now, before the arrest. ^[9]

Tube size, blade and depth (4 marks). Uncuffed internal diameter equals age over 4 plus 4, giving 5.0 mm; cuffed equals age over 4 plus 3.5, giving 4.5 mm. Depth at the lips equals age over 2 plus 12, giving 14 cm, or about three times the internal diameter. A curved Macintosh size 2 blade is appropriate for this four-year-old; the straight Miller blade is reserved for the infant, whose long floppy epiglottis must be lifted directly. ^{[1] [11]}

The seven-step procedure (6 marks). (1) Prepare and check: tube size plus one half-size up and down, working laryngoscope, suction, stylet, cuff syringe, securing tape, capnography sensor. (2) Preoxygenase with 100 per cent oxygen for two to three minutes. (3) Position: sniffing position in the older child, neutral with a towel under the shoulders in the infant. (4) Induce and paralyse in a rapid sequence. (5) Laryngoscopy: insert the blade, lift (do not lever) to expose the glottis, pass the tube through the cords under direct vision, withdraw the stylet. (6) Confirm with waveform capnography, a square-wave trace over six breaths, with chest rise and equal air entry. (7) Secure the tube, verify the depth, and order a confirmatory chest radiograph. ^[11]

Reasoning (2 marks). The infant airway is high and anterior with a large tongue and floppy epiglottis, which is why positioning, the correct blade, and a single calm first look matter. Preoxygenation extends the safe apnoea time and is the act that prevents the commonest complication, hypoxia from a prolonged attempt. ^[11]