Optimal Insertion Depth for Endotracheal Tubes in Extremely Low-Birth-Weight Infants

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To determine the optimal endotracheal tube insertion depth in extremely low-birth-weight infants based on the association between endotracheal tube depth and gestational age, body weight, body length, and head and chest circumferences at birth.


Retrospective chart review.


Neonatal ICU at a medical center.


Fifty-two hospitalized extremely low-birth-weight infants in our neonatal ICU.



Measurements and Main Results:

Data regarding gestational age, body weight, body length (crown–heel length), head and chest circumferences, and final endotracheal tube depth were retrieved from the medical records of 52 newborn infants weighing less than or equal to 1,000 g at birth (boys, 29; girls, 23). The mean gestational age was 25.1 (range, 22–32) weeks, and the mean body weight was 724.5 (range, 400–1,000) g. Of the endotracheal tubes used, 3%, 87%, and 10% of endotracheal tubes were of size 2.0, 2.5, and 3.0, respectively. Linear regression analysis revealed a significant association between endotracheal tube depth and gestational age, body weight, body length, head, and chest circumferences (p < 0.001). Body weight had the highest coefficient of determination (r2 = 0.497), followed by body length (0.458), with all other variables having values of less than 0.4.


In extremely low-birth-weight infants, a linear association exists between endotracheal tube insertion depth and gestational age, body weight, body length, chest, and head circumferences at birth. Although body weight is the most accurate method for predicting endotracheal tube insertion depth, body length is also appropriate and is more favorable than body weight in delivery room resuscitation. Although no substitute for radiologic confirmation exists, a tape measure that can convert body length to endotracheal tube depth may be helpful.

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