Cormack-Lehane and Modified Cormack-Lehane grading systems for laryngoscopy

The Cormack-Lehane scale^[1] describes the best view of the glottis during laryngoscopy, with grades defined by the structures that can be seen, as follows:

• Grade 1 – Most of the glottis
• Grade 2 – Only the posterior extremity of the glottis
• Grade 3 – Only the epiglottis
• Grade 4 – Neither the glottis nor the epiglottis

Difficult laryngoscopy is usually defined as a grade 3 or 4 view.

A modified version^[2] of the Cormack-Lehane grading system divides Grade 2 into Grade 2a and 2b:

• Grade 2a – Only part of the vocal cords is visible
• Grade 2b – Only the arytenoids or the very posterior origin of the cords are visible

A further modification^[3] divides Grade 3 as follows:

• Grade 3a - Epiglottis can be seen and lifted (eg, with a bougie)
• Grade 3b - Epiglottis can be seen but not lifted