Predicting the difficult airway

Difficult to Bag Ventilate

Difficult BVM (MOANS)

  • Mask seal
  • Obesity
  • Aged
  • No teeth
  • Stiffness (resistance to ventilation)

Difficult to Intubate (LEMON)

An airway assessment score based on criteria of the LEMON method is able to successfully stratify the risk of intubation difficulty in the emergency department.[1]


  • Look at the patient externally for characteristics that are known to cause difficult laryngoscopy, intubation or ventilation[2]
  • Trauma
  • Short neck
  • Micrognathia
  • Prior surgery
  • May also be difficult to bag
    • Body mass index
    • Advanced age
    • Beard
    • No teeth
    • Snoring
    • Dentures

Evaluate 3-3-2-1

3-3-2 ruleDistance between patient's incisor teeth of 3 finger breadths and distance between the thyroid notch and the floor of the mouth should be at least 2 finger widths
  • 3 - Ideally the distance between the patient's incisor teeth should be at least 3 finger breadths
  • 3 - Distance between the hyoid bone and the chin should be at least 3 finger breadths
  • 2 - Distance between the thyroid notch and the floor of the mouth should be at least 2 finger breadths
  • 1 - Lower jaw should not sublux more than 1cm


Mallampati Score
  • The patient sits upright, opens mouth and protrudes tongue
  • Grades are based on visibility of the uvula, posterior pharynx, hard, and soft palate


Neck Mobility

  • Patient places chin down onto their chest and extend their neck.
  • Remove the hard collar and provide manual stabilization in trauma patients.
  • Poor neck mobility impacts ability to have airway access alignment.

See Also

Airway Pages


  1. Reed, M. et al. Can an airway assessment score predict difficulty at intubation in the emergency department? Emerg Med J. 2005 Feb; 22(2): 99–102. doi: 10.1136/emj.2003.008771
  2. Rennie LM, Dunn MJG, et al. Is the ‘LEMON’ method an easily applied emergency airway assessment tool? European Journal of Emergency Medicine 2004;11:154–7


Ross Donaldson