Cormack-Lehane classification system
The Cormack-Lehane system classifies views obtained by direct laryngoscopy based on the structures seen. It was initially described by R.S. Cormack and J. Lehane in 1984 as a way of simulating potential scenarios that trainee anaesthetists might face. A modified version that subdivided Grade 2 was initially described in 1998.
| Grade | Description | Approximate frequency | Likelihood of difficult intubation |
| 1 | Full view of glottis | 68-74% | <1% |
| 2a | Partial view of glottis | 21-24% | 4.3-13.4% |
| 2b | Only posterior extremity of glottis seen or only arytenoid cartilages | 3.3-6.5% | 65-67.4% |
| 3 | Only epiglottis seen, none of glottis seen | 1.2-1.6% | 80-87.5% |
| 4 | Neither glottis nor epiglottis seen | very rare | very likely |