⚠️ Chapter 22: Difficult Intubation

LEMON mnemonic · Modified Mallampati · 3-3-2 rule · Difficult airway predictors · CVCI (cannot intubate, cannot ventilate) · Needle cricothyroidotomy · Airway adjuncts (LMA, fibre-optic, lightwand) · Extubation planning

🔍 Core Concepts: Difficult Intubation

📌 Definition
Situation where conventionally trained anaesthesiologist experiences difficulty with face mask ventilation, laryngoscopy, intubation, or combination. Suspected difficult airway is a contraindication to RSI.
🔍 Prediction: LEMON
L: Look externally (obesity, facial trauma, large tongue). E: Evaluate 3-3-2 (interincisor 3 fingers, hyoid-mental 3 fingers, thyroid-floor of mouth 2 fingers). M: Mallampati (I-IV). O: Obstruction. N: Neck mobility.
📐 Modified Mallampati
Class I: visible soft palate, uvula, pillars. Class IV: only hard palate visible (most difficult). Higher class predicts difficult intubation.
⚙️ Difficult airway kit components
Alternative supraglottic devices (LMA, ILMA), video laryngoscope, fibre-optic bronchoscope, lightwand, retrograde intubation set, cricothyroidotomy kit, tube exchanger.
🚨 CVCI (Cannot Intubate, Cannot Ventilate)
Life-threatening emergency. Rescue: needle cricothyroidotomy with jet ventilation (1 sec on, 4 sec off) or surgical airway. Convert to definitive ETT.
📉 Extubation of difficult airway
Have reintubation plan, airway kit, consider awake extubation over tube exchanger, prepare for tracheostomy if needed. Never extubate without securing backup.

🩺 Stepwise Approach: Difficult Intubation Management

1
Anticipate & predict using LEMON
Apply LEMON mnemonic. Look externally (obesity, facial abnormalities, large tongue). Evaluate 3-3-2 (mouth opening, hyoid-mental distance, thyroid-notch to floor). Mallampati score. Assess for obstruction (stridor, mass). Neck mobility (C-spine pathology).
2
Prepare equipment & personnel
Difficult airway kit at bedside: video laryngoscope, LMA/ILMA, fibre-optic scope, tube exchanger, cricothyroidotomy kit. Call for experienced help (anaesthesiology, ENT). Have rescue surgical airway plan.
3
Consider awake intubation vs. induction
If predicted extremely difficult, perform awake intubation with topical anaesthesia + sedation preserving spontaneous breathing. If induction used, avoid muscle relaxants if CVCI risk. Use video laryngoscopy.
4
Primary & backup strategies
Plan A: direct laryngoscopy with optimal positioning/BURP. Plan B: video laryngoscopy or LMA. Plan C: fibre-optic intubation or lightwand. Plan D: surgical airway (cricothyroidotomy/tracheostomy).
5
CVCI (Cannot Intubate, Cannot Ventilate) rescue
If SpO2 drops <90% with failed intubation and inability to mask ventilate: needle cricothyroidotomy (14-16G catheter) with jet ventilation (1 sec on, 4 sec off) or scalpel cricothyroidotomy. Convert to definitive airway.
6
Difficult extubation planning
Never extubate a difficult airway without a reintubation plan. Use tube exchanger (airway exchange catheter) during extubation, maintain oxygenation. Have difficult airway kit ready. Consider elective tracheostomy for long-term.