Infant ETT Size Cuffed Formula — FRCA Final MCQ

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EasyPaediatric AnaesthesiaInfant ETT Size Cuffed FormulaFRCA Final

A child aged 18 months (11 kg) requires general anaesthesia for bilateral inguinal hernia repair. The appropriate endotracheal tube size using the age formula for a cuffed tube is:

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Correct answer: B — 3.0 mm

For children >1 year: Cuffed ETT size = (age/4) + 3.5. For 18 months (1.5 years): (1.5/4) + 3.5 = 3.875, rounded to 3.5 mm cuffed. For children <1 year, the standard cuffed tube size is 3.0-3.5 mm ID. However, at 18 months many centres would use a 3.5 mm cuffed tube. Uncuffed formula: (age/4) + 4 = (1.5/4) + 4 = 4.375, rounded to 4.0-4.5 mm uncuffed. Modern practice increasingly uses cuffed tubes in all age groups (including neonates >3 kg) with cuff pressure <20 cmH2O.

Reference: APA/DAS – 2015 – Paediatric airway guidelines; RCOA – 2023 – Paediatric module