Patient selection: subglottic stenosis
Method of determining the size of the trachea at the site of obstruction:
(1) Determine the largest endotracheal tube that will pass through the point of obstruction.
(2) Make sure that the tube can tolerate normal leak pressures (10-25 cm H2O).
(3) Measure the external/outside diameter of the tube.
Method of normal tracheal size – one of the following:
(1) diameter of unaffected trachea by ultrasound or other imaging method
(2) outside diameter of the age-expected endotracheal tube size (see 08.32)
cross-sectional area in square cm =
= PI() / 4 * ((outside diameter in cm)^2)
percent stenosis =
= ((expected area) – (area of obstruction)) / (expected area) * 100%
|
Percent Obstruction
|
Grade
|
|
none
|
0
|
|
<= 50%
|
I
|
|
51 to 70%
|
II
|
|
71% to 99% (any detectable lumen)
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III
|
|
100% (no detectable lumen)
|
IV
|
where:
• At higher levels of obstruction it would be impossible to pass a standard endotracheal tube.
• Functionally a high grade stenosis would require a tracheostomy.
