Recommended Depth of Insertion for Endotracheal Tubes in Infants

For infants under 1 year of age, the recommended depth of insertion for endotracheal tubes at the lip is calculated as weight in kg + 6 cm. 1

Endotracheal Tube Size Selection

For emergency intubation of infants less than 1 year of age:
- If using a cuffed tube: select a 3.0 mm ID tube 1, 2
- If using an uncuffed tube: select a 3.5 mm ID tube 1, 2
Both cuffed and uncuffed endotracheal tubes are acceptable for intubating infants 2, 1
Cuffed tubes may be preferable in certain circumstances such as poor lung compliance, high airway resistance, or large glottic air leak 2, 1

Primary formula: Depth of insertion (cm at lip) = weight in kg + 6 cm 1, 3
Alternative method: Depth can be estimated as 3 times the internal diameter of the tube 1
For extremely low birth weight infants (<750g), the standard formula may result in tubes being placed too deep, requiring extra caution 4

After intubation, proper tube placement must be verified using multiple methods 1, 2:

Look for bilateral chest movement 2, 1
Listen for equal breath sounds over both lung fields, especially over the axillae 2
Check for exhaled CO2 (capnography or colorimetry) - considered the optimal method 2
If perfusing rhythm is present, monitor oxyhemoglobin saturation with pulse oximetry 2
In hospital settings, perform a chest x-ray to verify proper position in the midtrachea 2

Have tubes 0.5 mm smaller and 0.5 mm larger than the estimated size available during intubation 2, 1
Length-based resuscitation tapes are more accurate than age-based formulas for determining tube size in children up to 35 kg 2
If resistance is met during intubation, use a tube 0.5 mm smaller 2
If a large glottic air leak interferes with oxygenation or ventilation after intubation, consider replacing with a tube 0.5 mm larger or switching to a cuffed tube of the same size 2

ETTs are frequently incorrectly positioned in newborns, most often inserted too far 5, 6
Remember the "DOPE" mnemonic if a patient's condition deteriorates after intubation: Displacement, Obstruction, Pneumothorax, Equipment failure 2, 1
Maintain the patient's head in neutral position after securing the tube; neck flexion may push the tube further into the airway, while extension may pull it out 2, 1
The accuracy of weight-based formulas may be lower in extremely premature infants (<1 kg), with one study showing only 47% accuracy in predicting proper ETT depth 6
Recent research comparing weight-based and nasal-tragus length (NTL) formulas shows mixed results, with some studies suggesting NTL+1 cm may be better for term neonates 7, while others found similar or worse results with NTL in preterm infants 3

For infants weighing <750g, the standard weight-based formula may position the ETT too low 4
For these extremely small infants, more frequent radiographic assessment and potential adjustments may be necessary 6, 4
Consider reducing the calculated depth slightly for infants <750g to avoid endobronchial intubation 4