What is the recommended size of an Endotracheal (ET) tube for adults and children?

Endotracheal Tube Size Selection

Use length-based resuscitation tapes for children up to 35 kg, and for adults, select 7.0-8.0 mm tubes for women and 8.0-8.5 mm tubes for men based on height, with specific pediatric formulas available for age-based estimation when tapes are unavailable. 1

Pediatric Patients

Infants Under 1 Year

• Cuffed tube: 3.0 mm internal diameter (ID) 1, 2
• Uncuffed tube: 3.5 mm ID 1, 2
• Both cuffed and uncuffed tubes are acceptable, though cuffed tubes may be preferable in cases of poor lung compliance, high airway resistance, or large glottic air leak 1

Children 1-2 Years

• Cuffed tube: 3.5 mm ID 1, 3
• Uncuffed tube: 4.0 mm ID 1

Children Over 2 Years

Use these formulas for rapid estimation: 1

• Cuffed tube: ID (mm) = 3.5 + (age in years ÷ 4)
• Uncuffed tube: ID (mm) = 4.0 + (age in years ÷ 4)

Critical Preparation Step

Always have tubes 0.5 mm smaller and 0.5 mm larger than your estimated size immediately available at the bedside 1. If you meet resistance during intubation, use the smaller tube; if there is excessive air leak compromising ventilation, consider the larger tube or switch to a cuffed tube of the same size 1.

Depth of Insertion for Pediatrics

Use this formula: Depth at lip (cm) = weight in kg + 6 cm 2, 3

Alternatively, depth = 3 × internal diameter of the tube 2, 3

Adult Patients

Standard Sizing by Sex

• Women: 7.0-7.5 mm ID 4
• Men: 8.0-8.5 mm ID 4

Height-Based Considerations

Tracheal diameter varies significantly with height and sex, being narrowest at the subglottis 4, 5. Women and patients with height less than 160 cm are at higher risk of receiving inappropriately large tubes, which increases postoperative complications including sore throat and hoarseness 4, 5.

For shorter adults (height <160 cm), particularly women, consider using smaller tubes (6.0-6.5 mm ID) to reduce airway trauma 4, 5. These smaller tubes still accommodate standard intubation aids, suction catheters, and slim-line bronchoscopes without compromising ventilation 4.

Depth of Insertion for Adults

Use this formula: Optimal ETT length (cm) = (body height in cm ÷ 5) - 13, measured from 5 cm above the carina to the right mouth angle 6

Key Equipment Requirements

Emergency departments must stock the following tube sizes to accommodate all patients 1:

• Uncuffed: 2.5,3.0 mm
• Cuffed or uncuffed: 3.5,4.0,4.5.0,5.5 mm
• Cuffed: 6.0,6.5,7.0,7.5,8.0 mm

Verification of Proper Placement

Use multiple confirmation methods immediately after intubation (Class I, Level of Evidence B) 1:

• Visualize bilateral chest rise 1, 2
• Auscultate equal breath sounds bilaterally over the axillae 1, 2
• Confirm absence of gastric insufflation sounds 1, 2
• Verify exhaled CO₂ with capnography or colorimetry (most reliable method) 1, 3
• Monitor oxygen saturation with pulse oximetry if perfusing rhythm present 1, 2
• Obtain chest x-ray in hospital settings to confirm midtracheal position 1, 2

Critical Pitfalls to Avoid

The DOPE Mnemonic

If an intubated patient deteriorates, immediately assess for 1, 2:

• Displacement of the tube
• Obstruction of the tube
• Pneumothorax
• Equipment failure

Cuff Management

When using cuffed tubes, monitor and limit cuff inflation pressure to less than 20-25 cm H₂O per manufacturer instructions 1. Cuffed tubes decrease aspiration risk but require vigilant pressure monitoring 1, 3.

Head Position

Maintain the patient's head in neutral position after securing the tube—neck flexion pushes the tube deeper while extension pulls it out 1, 2.

Length-Based Tapes vs. Formulas

Length-based resuscitation tapes are more accurate than age-based formulas for children up to 35 kg, even in children with short stature 1. Use formulas only when tapes are unavailable or the patient exceeds 35 kg.