LEMON Airway Assessment
Structured difficult airway prediction using the LEMON mnemonic — Look externally, Evaluate 3-3-2 rule, Mallampati classification, Obstruction assessment, and Neck mobility. Scores 0–10 with management guidance.
Low Risk
L:0 · E:0 · M:0· O:0 · N:0
Look Externally
External features predicting difficult laryngoscopy & ventilation (0-4 pts)
Evaluate 3-3-2 Rule
Three finger-breadth measurements — 1 point per unfavourable (0-3 pts)
Measurement 1 (3 FB): Inter-incisor distance — between upper and lower incisors with mouth fully open
Measurement 2 (3 FB): Hyoid-mental distance — from chin (mentum) to hyoid bone along floor of mouth
Measurement 3 (2 FB): Thyroid-to-floor-of-mouth — from thyroid notch superiorly to hyoid bone
Mallampati Score
Oropharyngeal view — Class III or IV scores 1 point (0-1 pt)
Obstruction
Any condition causing upper airway obstruction (0-1 pt)
Neck Mobility
Ability to flex and extend the neck — sniffing position (0-1 pt)
Normal: chin to chest, ability to look at ceiling (atlanto-occipital extension).
Reduced in: cervical spine disease, C-spine immobilisation (hard collar), rheumatoid arthritis, ankylosing spondylitis, previous cervical fusion.