What are the guidelines for endotracheal (ET) tube size, depth of insertion, and laryngoscope blade selection for intubation in children under 1 year of age?

Endotracheal Tube Selection and Intubation Guidelines for Children Under 1 Year of Age

For infants under 1 year of age, use a 3.0 mm ID cuffed endotracheal tube or a 3.5 mm ID uncuffed endotracheal tube for emergency intubation, with depth of insertion based on the formula "weight in kg + 6 cm" at the lip, and a straight laryngoscope blade (size 1) for optimal visualization. 1

Endotracheal Tube Size Selection

Cuffed vs. Uncuffed Tubes

• Both cuffed and uncuffed endotracheal tubes are acceptable for intubating infants under 1 year of age (Class IIa, LOE C) 1
• For emergency intubation of an infant less than 1 year of age:
  • If using a cuffed tube: select a 3.0 mm ID tube 1
  • If using an uncuffed tube: select a 3.5 mm ID tube 1

Advantages of Cuffed Tubes

• Cuffed tubes may be preferable in certain circumstances such as poor lung compliance, high airway resistance, or large glottic air leak (Class IIa, LOE B) 1
• Cuffed tubes reduce the need for tube exchange (very low-quality evidence) 2
• Cuffed tubes may decrease the risk of aspiration 1
• If using cuffed tubes, monitor cuff inflation pressure and limit according to manufacturer's instructions (usually less than 20-25 cm H2O) 1

Preparation Tips

• Have tubes 0.5 mm smaller and 0.5 mm larger than the estimated size available during intubation 1
• Length-based resuscitation tapes are more accurate than age-based formulas for determining tube size in children up to 35 kg 1
• If resistance is met during intubation, use a tube 0.5 mm smaller 1
• 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 1

Depth of Insertion

While the American Heart Association guidelines don't specifically address depth of insertion for infants under 1 year, the commonly accepted formula is:

• Depth of insertion (cm at lip) = weight in kg + 6 cm 1
• Alternatively, the depth can be estimated as 3 times the internal diameter of the tube

Laryngoscope Blade Selection

• For infants under 1 year, a straight blade (typically Miller size 1) is generally preferred as it provides better visualization by lifting the epiglottis directly 1
• The blade size should be appropriate for the infant's size, with size 1 being standard for most infants under 1 year 1

Verification of Tube Placement

After intubation, verify proper tube placement using multiple methods (Class I, LOE B) 1:

• Look for bilateral chest movement 1
• Listen for equal breath sounds over both lung fields, especially over the axillae 1
• Listen for absence of gastric insufflation sounds over the stomach 1
• Check for exhaled CO2 1
• If perfusing rhythm is present, monitor oxyhemoglobin saturation with pulse oximetry 1
• If uncertain about placement, perform direct laryngoscopy to visualize the tube between the vocal cords 1
• In hospital settings, perform a chest x-ray to verify proper position in the midtrachea 1

Common Pitfalls and Considerations

• Remember the "DOPE" mnemonic if a patient's condition deteriorates after intubation: Displacement, Obstruction, Pneumothorax, Equipment failure 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 1
• Tube replacement carries risks and should be performed in an appropriate setting by experienced personnel 1
• Ultrasound measurement of the minimal transverse diameter of the subglottic airway may help in selecting the appropriate ETT size and potentially reduce the number of reintubations 3