What it is
After a neonatal intubation, the tube has to sit in mid-trachea — too deep and it slides into the right main bronchus, too shallow and it extubates with the next reposition. This tool gives a weight-based estimate of the insertion depth at the lips (oral) for a newborn, with a second independent rule shown alongside so you can sanity-check before the confirmatory CXR.
Formula
$$ Depth,(cm) = 1.17 \times birthWeight,(kg) + 5.58 $$
A bedside cross-check, the classic Tochen “6 + weight” rule:
$$ Depth,(cm) \approx 6 + birthWeight,(kg) $$
The two should land within a few millimetres of each other across the normal-term range; a large divergence is a prompt to re-measure the weight.
When to use
Emergent or planned orotracheal intubation of a neonate, to set an initial depth that you then confirm by auscultation and chest radiograph. It is a starting estimate, not placement confirmation.
Worked example
A 3 kg term newborn:
$$ Depth = 1.17 \times 3 + 5.58 = 9.1\ \text{cm at lips} $$
The 6 + weight rule gives 6 + 3 = 9.0 cm — agreement within 1 mm, so 9 cm is a reasonable first depth pending CXR.
Pitfalls
- Confirm, don’t trust the number. Auscultate for symmetric air entry and verify tip position (T2–T3, ~1 cm above the carina) on CXR.
- ELBW infants break the rules. The Tochen 6 + weight rule overestimates depth in extremely-low-birthweight infants, especially < 750 g, where ~6 cm fixed insertion may be more appropriate. Do not extrapolate the regression below its validated range.
- Oral vs nasal: this estimates the oral/lip depth — add for a nasotracheal route.
- Gestational age and nasal-tragus length methods exist and may outperform weight in the smallest babies — use the tool your unit has validated.
- Re-check depth after any head repositioning; neck flexion advances the tube.
Run it: ET Tube Depth (Neonatal)
Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.