Endotracheal intubation and emergency airway equipment — branching viva

Branching viva — endotracheal intubation

The examiner releases the stem and then branches into five probes. A strong candidate answers the indication first, defends the anatomy, demonstrates the technique, gives the drug regimen, and names the complications without prompting.

Opening (examiner)

"A four-year-old with bacterial tracheitis arrives drooling, sitting forward, retracting hard, and now drowsy. The saturation is falling despite high-flow oxygen. What is your next move?" [9]

Branch 1 — The indication (expected answer)

Secure the definitive airway now — he has a failing airway with impending loss of protection (drooling, drowsy, falling oxygenation). The indications are respiratory failure, a Glasgow Coma Scale of 8 or less, severe shock and cardiac arrest; he meets the first two. Intubate before the arrest, not after it. Assemble the team, preoxygenate, and prepare for rapid sequence intubation.

Probe. "Why a tube and not just a bag-mask?" — A bag-mask is the bridge and keeps most children alive, but it does not protect the lungs from aspiration, fatigues the operator, and cannot reliably deliver high pressures. Only a tube through the cords opens, protects and ventilates. [9]

Branch 2 — Sizing and blade (expected answer)

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 right for this four-year-old; the straight Miller blade is for the infant. [1] [11]

Probe. "Why a Miller blade in the infant?" — The infant epiglottis is long, soft and U-shaped and flops over the glottis. A straight Miller blade lifts it directly. The Macintosh sits in the vallecula and lifts indirectly through the hyoepiglottic ligament, which works once the larynx has descended in the older child. [11]

Probe. "Are cuffed tubes safe in children?" — Yes. Two Cochrane reviews found no increase in post-extubation stridor with modern cuffed tubes when sized correctly and the cuff pressure is monitored. Keep the cuff pressure below 25 cm of water. [1]

Branch 3 — Physiology and confirmation (expected answer)

The infant airway has four features that change technique: a large occiput, a large tongue, a high anterior larynx, and a long floppy epiglottis. The cricoid is the only complete ring and the narrowest point — the reason an uncuffed tube can still obstruct and an over-inflated cuff can ischaemic the mucosa. Confirm the tube with waveform capnography: a square-wave carbon dioxide trace over six breaths is the standard. [5] [11]

Probe. "Why capnography and not chest rise?" — Chest rise, breath sounds and condensation are all produced by an oesophageal intubation. Only a sustained capnography trace confirms tracheal placement. A colorimetric detector is secondary and unreliable in low cardiac output. [5]

Branch 4 — Rapid sequence drugs (expected answer)

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 — then a neuromuscular blocker: rocuronium 1 mg per kg is increasingly first-line; succinylcholine 1 to 2 mg per kg is faster but contraindicated in hyperkalaemia, burns over 24 hours old, muscle disease and malignant hyperthermia. Cricoid pressure is no longer routine. [7] [8]

Probe. "The child has burns — does that change the paralysing agent?" — Yes. Succinylcholine is contraindicated in burns more than 24 hours old because of hyperkalaemia. Use rocuronium 1 mg per kg. [7]

Branch 5 — Complications and disposition (expected answer)

Name and prevent them: hypoxia from prolonged attempts (preoxygenate, stop after a failed attempt and bag-mask ventilate); unrecognised oesophageal intubation (capnography); right main bronchus intubation (withdraw the tube until breath sounds are equal, confirm on a chest radiograph); bradycardia in the infant (stop, oxygenate, compressions if poorly perfused); post-extubation stridor and subglottic stenosis (correct size, cuff pressure below 25 cm of water, minimise attempts). Once secured, ventilate to target, confirm on a chest film, and secure and document before any transfer. [5] [11]

Probe. "You cannot see the cords on the first look — what now?" — Do not keep repeating direct laryngoscopy. Reposition, apply external laryngeal manipulation (BURP), and if still poor, switch to video laryngoscopy and have a supraglottic airway ready. A 2024 NEJM trial and a 2025 BJA systematic review support video laryngoscopy first-line for the difficult airway. [3] [9]

Examiner's wrap

Outcome is driven by the underlying illness, not by the act of intubation, but a secured, confirmed, monitored tube is what converts a failing airway into a survivable one. The two examinable absolutes are the age-based formulas and waveform capnography as the confirmation standard. [9] [11]