Glossary of Terms in Otolaryngology

Cotton-Myer Classification of Subglottic Stenosis

  • The Cotton-Myer Classification is used to grade the severity of subglottic stenosis.1
    • It was initially developed in 1994 and described as a way to grade subglottic stenosis using different endotracheal tube sizes.
    • See our image atlas for examples of subglottic stenosis.
  • The Cotton-Myer classification is divided into 4 grades depending on the degree of obstruction of the airway lumen:
    • Grade 1: 0-50% occlusion.
    • Grade 2: 51-70% occlusion.
    • Grade 3: 71-99% occlusion
    • Grade 4: no detectable lumen.
Grade From To
Grade I No obstruction 50% obstruction
Grade II 51% obstruction 70% obstruction
Grade III 71% obstruction 99% obstruction
Grade IV No detectable lumen
  • Cotton, O’Connor, and Myer further proposed that the degree of occlusion could be objectively measured intraoperatively by sizing the airway with different endotracheal tubes.
    • In this method, the caliber of the airway is measured by finding the largest endotracheal tube size that can fit through the airway while still maintaining an air leak.
    • This was measured at up to 25 cm H2O of pressure in the original paper.
    • A reference table (see below) is then used to obtain the percentage of obstruction based on the endotracheal tube size as well as the patient’s age.
Age Percent Obstruction with ETT Size
ETT Size (ID) 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
Premature 0 0 0 0 0 0 0 0 0
40% 0 0 0 0 0 0 0 0
58% 30% 0 0 No obstruction 0 0
0-3 months 68% 48% 26% 0 0 0 0 0 0
3-9 months 75% 59% 41% 22% 0 0 0 0 0
9 months - 2 years 80% 67% 53% 38% 20% 0 0 0 0
2 years 84% 74% 62% 50% 35% 19% 0 0 0
4 years 86% 78% 68% 57% 45% 32% 17% 0 0
6 years 89% 81% 73% 64% 54% 43% 30% 16% 0
GRADE IV
(No lumen)		 GRADE III GRADE II GRADE I
Adapted from: Myer III, Charles M., David M. O’Connor, and Robin T. Cotton. “Proposed grading system for subglottic stenosis based on endotracheal tube sizes.”

  1. Myer III, Charles M., David M. O’Connor, and Robin T. Cotton. “Proposed grading system for subglottic stenosis based on endotracheal tube sizes.” Annals of Otology, Rhinology & Laryngology 103.4 (1994): 319-323. ↩

Last updated October 20, 2022
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