Student Pontifícia Universidade Católica do Rio Grande do Sul Porto Alegre, Rio Grande do Sul, Brazil
Background: Extremely low birth weight (ELBW) and extremely preterm (EP) infants lack precise methods for determining the optimal depth of endotracheal tube (ETT) placement, with mid-tracheal alignment between T1-T2 vertebrae as a radiographic reference point. Malpositioned ETTs increase the risk of complications, including uneven surfactant distribution, tissue damage, and inadvertent extubation. Objective: To compare three methods (Neonatal Resuscitation Program 8, Duke Formula, and 7-8-9 Rule) used to estimate ETT depth in infants and identify which is most accurate at predicting optimal placement. Design/Methods: This was a single-center retrospective study of neonates with a birth weight (BW) < 1000 g and gestational age (GA) < 28 weeks who required intubation between January 2021 and July 2023. Initial ETT depth and adjustments were obtained from chart review, and radiographs were assessed for ETT position. Infants lacking confirmation imaging were excluded. The prediction criteria were as follows: NRP (23-24 weeks: 5.5 cm / 25-26 weeks: 6.0 cm / 27-29 weeks: 6.5 cm), Duke Formula (5.0 cm + 1 cm/kg for infants < 500 g / 5.5 cm + 1 cm/kg for infants 500-999 g), and 7-8-9 Rule (6.0 cm + 1 cm/kg). Results: The intubations of 109 infants were included. The mean BW was 778.8 g and the mean GA was 26 weeks. The majority of infants (64.2%) did not have an appropriate ETT position in the first X-ray and most required repositioning (62.4%). The Pearson correlations of the different tools with the final ETT position were the following: NRP PC=0.599, Duke PC=0.735, and 7-8-9 PC=0.756 (p < .001). The Bland-Altman plots of methods and their final position demonstrates an overestimated depth with Duke and 7-8-9, while NRP underestimated it.
Conclusion(s): There is substantial variability when comparing three methods for ETT placement in this population, and depending on the method used, the magnitude of the measurement value may influence the agreement between the placement method and the final ETT depth. In our sample, the 7-8-9 rule had the strongest correlation with the final ETT position; however, the paired measurements exhibited a strong positive trend. The correlation between the Duke method and the final ETT was similarly strong (r = 0.74), and while it also exhibited a significant trend, the trend was driven by the highest 25% of measurements. While the correlation between NRP and the final ETT depth was less strong than the other two methods, paired NRP and ETT measurements were randomly scattered around the bias line and all points fit between the 95% limits of agreement. IMG_0947.jpeg
