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