Estimate percent subglottic obstruction and Cotton-Myer grade from patient age and the largest endotracheal tube that passes the stenosis.
| Age | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 4.5 | 5.0 | 5.5 |
|---|---|---|---|---|---|---|---|---|
| Pre-term (younger) | 40% | – | – | – | – | – | – | – |
| Pre-term (older) | 58% | 30% | – | – | – | – | – | – |
| 0–3 months | 68% | 48% | 26% | – | – | – | – | – |
| 3–9 months | 75% | 59% | 41% | 22% | – | – | – | – |
| 9 months – 2 years | 80% | 67% | 53% | 38% | 20% | – | – | – |
| 2 years | 84% | 74% | 62% | 50% | 35% | 19% | – | – |
| 4 years | 86% | 78% | 68% | 57% | 45% | 32% | 17% | – |
| 6 years | 89% | 81% | 73% | 64% | 54% | 43% | 30% | 16% |