Myer-Cotton Grade of Subglottic Stenosis Depends on Style of Endotracheal Tube Used.

OBJECTIVES

Determine percentage of subglottic stenosis using current endotracheal tube (ETT) cross-sectional areas as actual, compared with previously published ETT cross-sectional areas as expected, and determine if style of ETT could result in a change in percentage of stenosis or Myer-Cotton grade.

STUDY TYPE

Cross-sectional study.

DESIGN

Prospective analysis.

METHODS

Eight styles of uncuffed pediatric ETT from four manufacturers ranging from 2.0 to 6.0 inner diameter (ID) were evaluated. ID and outer diameter (OD) measurements were obtained from each company's specification sheets. Cross-sectional area was calculated for each ETT using the formula (Area = πr ). The cross-sectional areas of each current ETT (actual) were compared with those of previously published ETTs (expected) based on age, and the degree of stenosis was calculated using the formula [1- (Area /Area )] × 100%. Ranges of percentage for each style of ETT were calculated.

RESULTS

There was an increase in range of OD and area with increasing size of ETT ID, with the largest range in OD being 0.8 mm, and the largest range in area being 10.55 mm . The median interquartile range (IQR), range of percentage stenoses was 11 (5%), ranging from 0% to 21%. Seven of 28 (25%) ranges were found to span two Myer-Cotton grades.

CONCLUSIONS

The Myer-Cotton grade of subglottic stenosis depends on the style of ETT used. Using updated values from currently available ETTs aims to keep this grading system valid with respect to surgical approach and outcomes following surgery.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:2808-2812, 2023.