Accuracy of various recent recommendations to estimate the optimal depth of orotracheal tube in Thai neonates.

Background: Malposition of an endotracheal tube (ETT) may lead to many serious consequences. Recently, various methods have been proposed to estimate the proper position of orotracheal intubation (Pro-depth) for neonates.

Objectives: To determine and compare the accuracy of various methods for estimating the Pro-depth and to define the most accurate method for the Asian population.

Method: This cross-sectional study was conducted at the Chiang Mai University Hospital, Thailand in Asian neonates who required orotracheal intubation and their ETT's position were confirmed with anteroposterior chest radiographs. The estimated depths of orotracheal tubes (Est-depth) were calculated by using 4 methods: the rule of 7-8-9, NTL + 1 cm, corrected gestational age (GA)-based table, and body weight (BW)-based table. We defined the Pro-depth as the depth which provided the ETT's tip placed at mid trachea. The Pearson's correlation coefficient, the Bland-Altmann plot and mean differences with standard deviation (SD) between paired Est-depth by each method and Pro-depth were determined. New formulae were generated to estimate the Pro-depth based on a linear regression equation. The accuracy of each method to predict the optimal depth of orotracheal intubation (Opt-depth) was calculated.

Results: Fifty-eight Asian neonates were enrolled of which, 82.8% were Thai. The mean ± SD of GA and BW were 33 ± 5 weeks and 1562 ± 842 g, respectively. NTL + 1 cm and the Pro-depth showed the strongest correlation ( = 0.90, -value < .01) and agreement with mean difference ± SD of 0.28 ± 0.53 cm. The accuracies of the rule of 7-8-9, NTL + 1cm, corrected GA-based and BW-based table to predict the Opt-depth were 56.9%, 63.8%, 62.1%, and 60.3%, respectively. We created two simple formulae for our population to increase the accuracy of NTL parameter: NTL + 1 cm for measured NTL ≤ 6.5 cm and NTL + 0.5 cm for measured NTL > 6.5 cm. This new method provided more accuracy (72.4%) with mean difference ± SD of -0.03 ± 0.53 cm.

Conclusion: NTL was the most suitable parameter for estimating the Pro-depth. Our new modified NTL method should be used for Thai neonates with high accuracy and non-significantly underestimated trend. However, promptly clinical assessment and final confirmation by a chest radiography should be done in all intubated patients.