First, a quick poll – How do you determine ETT depth in kids?
What’s your method? Take the poll!
Written by Aaron Lacy
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Formula-based calculations for ETT depth in pediatric patients are based on a linear curve, despite children’s growth not being linear or uniform. Looking at age, height, and weight, these authors provide ETT depth recommendations based on calculated best-fit curves.
Not too deep, not too shallow: The Goldilocks zone for ETT depth
Given the small margin of error, ETT malposition is common in pediatric patients. I was trained to calculate ETT depth for peds patient with a formula. However, formulas provide a recommendation based on a linear scale, and children come in all shapes and sizes and don’t grow in a linear fashion. These authors reviewed associated diagnostics of 167 pediatric intubations (neonates excluded) and used regression analysis to create optimal best-fit curves for ETT depth based on weight, height, and age. They also compared their best-fit curves to several published formulas for proposed pediatric ETT depth. Overall, they found that any weight-related linear formula is unsuitable for determining appropriate ETT depth in children.
The authors found that linear formulas for both age and height were within an acceptable (95% prediction bands) range compared to their best fit curves. A proposed height-related ETT insertion depth chart is below.
How will this change my practice?
I don’t often intubate children, so when I do, I must recognize that I could be prone to cognitive overload. I doubt in a critical situation I could recite a linear formula off the top of my head, so I will likely be relying on a peripheral brain to help remember appropriate ETT insertion depth. If I am going to have to look it up anyway, I will be looking up this chart to make sure I am inserting the tube to the optimal depth. This chart would be a good addition to a pediatric intubation safety bundle.
Editor’s note: I’ve always taken the ETT size x 3 as the depth. I tested it out on the table above, and this may put you a little deep as kids approach age 10 years, but it gets you pretty close. ~Clay Smith
Source
Recommendations for endotracheal tube insertion depths in children. Emerg Med J. 2023. Aug;40(8):583-587. Doi: 10.1136/emermed-2022-212494.
So as an anesthesiologist, I personally never think about depth prior to the intubation. Most of my intubations are on pediatric patients but currently I am doing more nasal intubations for dental procedures than oral intubations. For T & A’s, I look after the intubation at the depth to the the lower front teeth, and chart that as well as notify the ENT. For the 3 to 8 year old patients that varies usually from 9 to 13 cm. But this is always a post hoc measurement, after I’ve seen the cuff pass the vocal cords and checked for bilateral breath sounds. I never even look at the depth for nasal intubations, in many cases of which I used an uncuffed tube. I use age divided by 4 plus 4 as a guide for ETT size, but often go down a half size if using a cuffed tube. On rare occasions I have had a nasal tube end up in the right mainstem and have to back the natural curve of the nasal tube away from the patient’s nare with a gauze padding over the bridge of the nose to get equal breath sounds, but that is only a handful of cases over many years of practice.