How to calculate suction catheter size for ETT
Suction Catheter Size – Easy Mnemonic
Mnemonic: “Age ÷ 2 + 8”
This is a commonly used formula for estimating suction catheter size in French (Fr) for children.
Neonates: 5–6 Fr
Infants: 6–8 Fr
Children: Age (years) ÷ 2 + 8 Fr
Adults: 12–16 Fr
- Important: Select a catheter that occupies less than half the internal diameter of the endotracheal tube (ETT) to reduce airway obstruction during suctioning.
Suction Catheter Size for ETT – Mnemonic
Mnemonic: ETT Size × 2
– Adult ETT: Suction catheter size (Fr) ≈ ETT internal diameter (mm) × 2.
ETT size | Suction catheter |
|---|---|
2.5 mm | 5 Fr |
3.0 mm | 6 Fr |
3.5 mm | 6–8 Fr |
4.0 mm | 8 Fr |
4.5 mm | 8 Fr |
5.0 mm | 10 Fr |
5.5 mm | 10 Fr |
6.0 mm | 10–12 Fr |
6.5 mm | 12 Fr |
7.0 mm | 12–14 Fr |
7.5 mm | 14 Fr |
8.0 mm | 14–16 Fr |
Important clinical point: The suction catheter should occlude less than 50% of the ETT lumen in adults and children (and generally less than 70% in neonates). Always follow your hospital’s protocol.
Exam tip: Remember ETT × 2 = French size (approximate).
