LANDMARK: The Cotton-Myer grading system for subglottic stenosis

Article: Proposed Grading System for Subglottic Stenosis Based on Endotracheal Tube Sizes

Myer CM, O’connor DM, Cotton RT. Proposed grading system for subglottic stenosis based on endotracheal tube sizes. Ann Otol Rhinol Laryngol. 1994;103(4 Pt 1):319-23.

Take Home Points:

  • The proposed Cotton-Myer grading system results in a more appropriate division of the patient population than previous grading systems (e.g. in the modified Cotton system (1989), most patients were in Grade 1).
  • The use of endotracheal tube as a reference standard reduces subjectivity present in other grading systems.

The Details:

  • Study Type: Description of a proposed classification system
  • Grading system intended for: Children with firm, mature subglottic stenosis (confirm using rigid laryngoscopy). Limited to subglottic stenosis in the following forms (including combinations): anterior subglottic stenosis, posterior subglottic stenosis, lateral subglottic stenosis, circumferential subglottic stenosis.
  • Grading system not intended for: Excludes patients with immature stenosis, suprastomal collapse, supraglottic collapse, suprastomal granulation tissue, laryngomalacia, tracheomalacia, vocal cord paralysis and tracheal stenosis.
  • Endotracheal tube estimated to fit into smallest part of stenosis inserted and replaced, as necessary, so audible leak pressure equaled 10cm-25 cm.
  • Based on the endotracheal tube which fit, and the patient age, the percentage obstruction can be found and grade can be assigned using Fig. 2.
  • The authors obtained percentage obstruction by comparing cross-sectional area (using outer diameter) of the endotracheal tube that would fit patient (with audible leak pressure 10 cm – 25 cm) and that of expected endotracheal tube for the patient’s age. (Fig.2)
  • Subglottic stenosis graded from Grade 1 – Grade IV (worst) (Fig.1)


  • Risk of injury since this system may require multiple insertions of endotracheal tubes.
  • Not accurate for describing subtle changes in the airway.
  • May not provide accurate prognosis for patients with multiple sites of airway disease.
  • Using leak pressure to determine which endotracheal tube is appropriate is not entirely accurate, particularly in cases where the shape of the stenosis differs greatly from tube shape.

* Percent obstruction in Figure 2 was calculated using the following formula: ((cross sectional area of age-appropriate endotracheal tube) – (cross sectional area of endotracheal tube that fits hypothetical patient/ (cross sectional area of age-appropriate endotracheal tube)) * 100

Summary contributed by Elizabeth Shay