The 3-3-2 rule is a bedside tool for identifying a patient who may be difficult to intubate.
These 3 measurements are part of the LEMON algorithm.
Patient selection: prior to intubation
3-3-2 refers to the number of finger breadths in external measurements.
Parameters:
(1) distance between upper and lower incisors
(2) hyoid to mental distance
(3) thyroid notch to floor of mouth
Parameter
Finding
Points
distance between upper and lower incisors with mouth wide open
3 or more finger breadths
0
0 to 2 finger breadths
1
hyoid-mental distance
thyroid notch to floor of mouth (thyroid to hyoid distance)
2 or more finger breadths
0 or 1 finger breadths
total score =
= SUM(points for the parameters)
Interpretation:
• minimum score: 0
• maximum score: 3
• A score of 0 is associated with a straightforward intubation.
• The risk of a difficult intubation increases as the score increases.
Limitations:
• The width of the examiner fingers may vary.
• The distances measured are affected by height and ethnicity resulting in interpatient variability.
To read more or access our algorithms and calculators, please log in or register.
Specialty: Anesthesiology, Surgery, general
