A Weight-based Formula for the Estimation of Gastric Tube Insertion Length in Newborns

Objective: Safe and effective functioning of nasogastric and orogastric tubes in the neonatal intensive care unit (NICU) is achieved by ensuring their correct placement within the stomach. Insertion length has traditionally been estimated using morphological measures, but studies have indicated that these are frequently inaccurate. This study aimed to evaluate the frequency of correct tube placement and to determine a weight-based formula for estimation of insertion length.

Study Design: A prospective study was performed over a 6-month period in a tertiary NICU. Infants with gastric tubes who required radiography for clinical reasons were included. The infant's weight and the type and length of tube were documented. A radiologist assessed the tube position to be high, borderline, correct, or long.

Results: A total of 218 radiographs of infants weighing 397 to 4131 g were included. Correct tube position was achieved on 74% of occasions. By analyzing data for correct tube positions, formulas were derived to predict tube insertion length in centimeters: orogastric = [3 × weight (kg) + 12] and nasogastric = [3 × weight (kg) + 13]. The formulas correctly predicted 60% of misplaced orogastric tubes and 100% of misplaced nasogastric tubes.

Conclusion: We propose a novel weight-based formula for estimation of gastric tube insertion length in newborn infants to improve the accuracy of this routine procedure.