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Optimal endotracheal tube insertion depth in infants with birth weights under 500 grams

Journal of Perinatology (2026)Cite this article

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Abstract

Objective

Develop a birth anthropometry-based model to estimate initial endotracheal tube (ETT) insertion depth for infants with birth weight <500 g.

Study design

Retrospective single center cohort (2010–2025) including infants with birth weight <500 g, intubated on day 0 and underwent a postintubation chest radiograph. Adequate depth was defined as lip-to-tip placement between the upper border of T1 and the lower border of T2. Linear and quadratic models using birth weight and length were compared; the final model was presented as a bedside nomogram.

Result

Eighty-two infants met the inclusion criteria. Birth weight and length independently predicted radiograph-derived optimal depth (p < 0.001). A combined quadratic model showed the strongest fit (adjusted R² = 0.70), outperforming single parameter rules.

Conclusion

In neonates <500 g, a quadratic weight-length model improves the prediction of radiograph-defined midtracheal ETT depth and offers a practical bedside guide for initial placement.

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Fig. 1: Relationship between birth parameters and optimal endotracheal tube (ETT) depth.
Fig. 2: Heatmap-based nomogram estimating optimal endotracheal tube (ETT) depth from birth weight and birth length.

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Data availability

All data generated or analyzed during this study are included in this article. Further enquiries can be directed to the corresponding author.

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Authors and Affiliations

  1. Department of Pediatrics, Asan Medical Center Children’s Hospital, University of Ulsan College of Medicine, Seoul, Republic of Korea

    Kyusang Yoo, Soo Hyun Kim, Jung Il Kwak, Tae-Gyeong Kim, Abraham Kwak, Juhee Park, Joo Hyung Roh, Jeong Min Lee, Ha Na Lee, Jiyoon Jeong, Chae Young Kim, Euiseok Jung & Byong Sop Lee

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  1. Kyusang Yoo
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Contributions

Kyusang Yoo conceptualized and designed the study, collected and analyzed the data, and drafted the initial manuscript. Soo Hyun Kim contributed to the conceptualization and design of the study, supervised the work, and critically revised the manuscript for important intellectual content. Jung Il Kwak, Tae-Gyeong Kim, Abraham Kwak, Juhee Park, Joo Hyung Roh, Jeong Min Lee, Ha Na Lee, Jiyoon Jeong, and Chae Young Kim contributed to data acquisition and manuscript review. Euiseok Jung and Byong Sop Lee provided a critical review and interpretation of the results. All authors approved the final manuscript and agree to be accountable for all aspects of the work.

Corresponding author

Correspondence to Soo Hyun Kim.

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Competing interests

The authors declare no competing interests.

Ethics

This study was approved by the Asan Medical Center Institutional Review Board (Approval No. 2025-1027). All methods were performed in accordance with the relevant guidelines and regulations. Given the retrospective nature of this study and the use of de-identified data, the requirement for informed consent was waived by the Institutional Review Board.

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Yoo, K., Kim, S.H., Kwak, J.I. et al. Optimal endotracheal tube insertion depth in infants with birth weights under 500 grams. J Perinatol (2026). https://doi.org/10.1038/s41372-026-02634-9

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