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]

SAQ 2 — Rapid sequence drugs, confirmation and complications (12 marks, 12 minutes)

A two-year-old in severe septic shock needs intubation. Vascular access is secured. The team is ready. [7] [11]

Question. Give the rapid sequence intubation drug regimen with doses, state how you confirm correct tube placement and why, and describe the complications you must prevent and how.

Model answer

Rapid sequence drugs (4 marks). Preoxygenase with 100 per cent oxygen first. Give a sedative: etomidate 0.3 mg per kg, ketamine 1 to 2 mg per kg, or propofol 2 to 4 mg per kg. Immediately follow with a neuromuscular blocker: rocuronium 1 mg per kg is increasingly first-line because it avoids the succinylcholine contraindications (hyperkalaemia, burns over 24 hours old, muscle disease, malignant hyperthermia); succinylcholine 1 to 2 mg per kg is the faster, shorter alternative. Cricoid pressure is no longer routine. [7] [8]

Confirmation (3 marks). Waveform capnography is the standard: a square-wave carbon dioxide trace over six breaths confirms tracheal placement, together with chest rise and equal breath sounds. Chest rise and condensation are also produced by an oesophageal intubation and are unreliable. A colorimetric detector is a secondary check and is unreliable in low cardiac output and arrest. The target end-tidal carbon dioxide after intubation is 35 to 45 mmHg. [5]

Complications and prevention (5 marks). Hypoxia from prolonged attempts is the commonest complication; prevent it with full preoxygenation and by stopping after a failed attempt to ventilate with a bag-mask before the next try. Unrecognised oesophageal intubation is the catastrophe and is prevented by capnography. Right main bronchus intubation from a tube too deep is corrected by withdrawing the tube until breath sounds are equal and confirming on a chest radiograph. Bradycardia in the infant is vagal and hypoxic; stop, ventilate with oxygen, and give chest compressions if poorly perfused. Post-extubation stridor and subglottic stenosis follow an over-sized or over-inflated tube; prevent them by correct sizing and a cuff pressure kept below 25 cm of water. Aspiration, pneumothorax and accidental extubation in transport complete the list. [11]

Disposition (2 marks). Once secured and confirmed, ventilate to a target oxygen saturation and end-tidal carbon dioxide, confirm tube position on a chest radiograph, and treat the underlying illness. A secured, monitored tube is the minimum standard before inter-hospital transfer; document the tube size, the depth and the airway plan. [9]