How do you perform a leak test on the endotracheal tube (ETT) cuff in a pediatric patient after intubation?

Performing a Leak Test for Endotracheal Tube Cuff in Pediatric Patients

After intubating a pediatric patient with a cuffed endotracheal tube, perform the leak test by deflating the cuff completely and applying positive pressure ventilation at 20-30 cm H₂O while auscultating over the larynx for an audible air leak around the tube. 1, 2

Standard Leak Test Technique

The recommended approach is to deflate the cuff entirely and deliver a positive pressure breath at 20-30 cm H₂O, then listen for an audible air leak at the mouth or over the larynx. 1

• An audible leak at ≤25-30 cm H₂O indicates appropriate tube size and positioning 1, 3, 4
• The presence of a small air leak confirms the tube is not too large and reduces risk of tracheal mucosal injury 1
• If no leak is audible at 30 cm H₂O with the cuff deflated, the tube may be too large and should be replaced with a tube 0.5 mm smaller in internal diameter 1

Critical Cuff Pressure Management After Leak Test

Once the leak test confirms appropriate tube size, re-inflate the cuff and immediately measure cuff pressure with a manometer, maintaining pressure at ≤20 cm H₂O in pediatric patients. 1, 2

• Pediatric airways require lower cuff pressures than adults due to smaller tracheal diameter and more compliant tissues 1, 2
• Never inflate the cuff based on clinical assessment alone, as pressures are consistently too high without objective measurement 1, 2
• Use a cuff pressure manometer as standard practice—this is not optional 1, 2

Alternative Quantitative Methods (Less Reliable in Pediatrics)

While quantitative leak tests exist, they have limited diagnostic accuracy in pediatric patients:

• Leak percentage test: Calculate (inspiratory tidal volume - expiratory tidal volume) × 100 / inspiratory tidal volume with cuff deflated 5
• Cuff leak percentage test: Calculate (expiratory Vt with inflated cuff - expiratory Vt with deflated cuff) × 100 / expiratory Vt with inflated cuff 5
• Recent evidence shows these quantitative methods have poor sensitivity (0.27-0.55) and specificity (0.35-0.81) for predicting post-extubation complications in children 5

Common Pitfalls to Avoid

Do not confuse the post-intubation leak test (to verify appropriate tube size) with the pre-extubation cuff leak test (to assess for laryngeal edema). 1, 6

• The post-intubation leak test is performed immediately after tube placement to confirm proper sizing 1
• The pre-extubation cuff leak test is performed before removing the tube after prolonged intubation to assess for airway edema 1
• These are two distinct procedures with different purposes and timing 6, 5

Never accept a tube with excessive air leak that compromises ventilation or oxygenation. 1

• If the leak is too large and interferes with achieving adequate tidal volumes, replace with a tube 0.5 mm larger or use a cuffed tube if an uncuffed tube was initially placed 1
• However, tube replacement carries risks and should be performed by experienced personnel in a controlled setting 1

Special Considerations for Cuffed Tubes in Pediatrics

Cuffed tubes are now preferred over uncuffed tubes in pediatric intensive care to reduce reintubation rates, provided cuff pressure is monitored and maintained ≤20 cm H₂O. 1

• The traditional dogma of avoiding cuffed tubes in children under 8 years is outdated 1
• Cuffed tubes reduce the need for tube exchanges due to excessive leak without increasing complications when cuff pressure is properly managed 1
• For infants ≥3.5 kg and <1 year, use a 3.0 mm internal diameter cuffed tube; for children 1-2 years, use 3.5 mm 1

Ensure the cuff is positioned below the vocal cords in the trachea, not within the larynx. 7

• Inappropriately high cuff position can cause severe laryngeal injury, granulation tissue, and web formation 7
• Verify tube depth using standard formulas and confirm with chest x-ray showing midtracheal positioning 1, 2