Article of the Month – November 2020

A Retrospective Evaluation of Airway Anatomy in Young Children and Implications for One-Lung Ventilation

Authors: Downard MG, Lee AJ, Heald CJ, Anthony EY, Singh J, Templeton WT.

URL: https://www.jcvaonline.com/article/S1053-0770(20)30809-0/fulltext

DOI: https://doi.org/10.1053/j.jvca.2020.08.015

Published: J Cardiothorac Vasc Anesth. 2020 September 10, in press.

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Article Description:

• Technological advancements in surgical thoracoscopy increase the need for lung separation in paediatric patients.
• Lung separation/isolation is challenging in children younger than 8 years.
• The use of endobronchial blocker and the endotracheal tube is usually considered for lung isolation at that age group.
• Few studies have measured lower airway anatomy in children < 8 years old.
• The objective of this study was to describe lower airway anatomy relevant to the establishment of one-lung ventilation in children younger than 8 years.

Summary:

• Chest computed tomographic scans of 111 children 4 days to 8 years of age were retrospectively reviewed.
• Measurements were taken from (1) the thyroid isthmus to the carina, (2) carina to first lobar branch on the left and right, (3) diameter of the trachea at the carina, and (4) diameter of the left and right mainstem bronchi.
• Dimensions were correlated with the outer diameter of endotracheal tubes and bronchial blockers.
• The left mainstem bronchus is consistently smaller than the right.
• The length from the carina to the first lobar branch on the left is consistently 3 times longer than on the right.
• Lung isolation using a mainstem technique on the left should use an ETT a half size smaller than would be used for tracheal intubation.
• Further, age-delineated bronchial diameters suggest that the clinician should transition from a 5F to a 7F Arndt bronchial blocker at 3-to-4 years of age.
• Linear regression fitting and algebraic transformation of depth as a function of the ID of cuffed ETT resulted in a more simplified expression for the depth of insertion.
• Right side OLV: Depth of placement (cm) = ([3.5 * age – appropriate cuffed ETT for oral intubation] + 1) cm
• Left side OLV: Depth of placement (cm) = ([3.5 * age – appropriate cuffed ETT for oral intubation] + 2) cm
• These simplified expressions correlated reasonably well with the depths calculated by the longer formula in most age groups, although the difference in these estimates increased in children aged 6 years and older.
• The primary limitation of this study was its retrospective design and a small number of patients.

Conclusion: A more detailed and accurate understanding of paediatric lower airway anatomy may assist the clinician in successfully performing OLV in young children.