Common Equations:
For any pediatric intubation, preparing multiple sizes of tubes is a good idea and don’t forget the Broslow tape is your friend.
Tube size cuffed: Age/4 +3
Tube size uncuffed: Age/4 +4
Tube depth: Age/2 +13 for greater than 1 year old; Weight/2 + 8 for under 1 year OR 3x ETT size
A Few Comments:
In researching this article, it turns out there are quite a few pediatric tube size equations. These are great to memorize as a reference but the ROC in the most recent meta-analysis was not very good, hence the prudence of preparing multiple tubes if time allows. To emphasize the point further, one recent prospective study found that the cuffed tube size equation, above, was only accurate in 21% of 204 patients. Furthermore, the tube depth equation had an ROC of .81 on a recent meta-analysis and review. Below are visual estimations and starting points for reference but no means a definitive sizing chart.
A detailed discussion can be found in the concepts tab here.
Preterm neonates:
Average weight: 2.5 kg
Tube size: 2.5 mm cuffed
Tube depth: 6-8 cm
Miller blade size: 00
LMA size: 0
Term Neonates:
Average weight: 3.3 kg
Tube size: 3.0 mm cuffed
Tube depth: 9 -10 cm
Miller blade size: 0
LMA size: 1
6 Months:
Average weight: 7.5 kg
Tube size: 3mm cuffed
Tube depth: 10 cm
Miller blade size: 1
LMA size: 1.5
1 – 2 Years:
Average weight: 9 – 11.5 kg
Tube size: 3.5 mm cuffed
Tube depth: 10 – 11 cm
Miller blade size: 1 or 2
LMA size: 1.5
3 – 4 Years:
Average weight: 14 – 15.5 kg
Tube size: 4 mm cuffed
Tube depth: 12 – 13 cm
Miller blade size: 2
Mac blade size: 2
LMA size: 2
5 – 6 Years:
Average weight: 17.6 – 20 kg
Tube size: 4.5-5 mm cuffed
Tube depth: 14 – 15 cm
Miller blade size: 2
Mac blade size: 2
LMA size: 2.5
12 Years:
Average weight: 31 kg
Tube size: 6.0 mm cuffed
Tube depth: 17 – 18 cm
Miller blade size: 2 or 3
Mac blade size: 3
LMA size: 3
References:
Estimation of optimal tube length: systematic review article on published formula for infants and children. Anaesthesist, 2016.
Endotracheal tubes in pediatric patients: published formulas to predict the optimal size. Anaesthesist, 2011.
Cuffed versus uncuffed endotracheal tubes in children: a meta-analysis. Journal of Anesthesia, 2016
Evaluation cuffed tracheal tube size predicted using the Kline formula in children. Pediatric Anesthesia, 2008
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