Anesth Pain Med.  2022 Oct;17(4):352-360. 10.17085/apm.22215.

Choice of the correct size of endotracheal tube in pediatric patients

• Park S
• Shin SW
• Kim HJ
• Byeon GJ
• Yoon JU
• Kim EJ
• Kim HY

• KMID: 2535333
• DOI: http://doi.org/10.17085/apm.22215

Abstract

Selection and insertion of an endotracheal tube (ETT) of appropriate size for airway management during general anesthesia in pediatric patients is very important. A very small ETT increases the risk of inadequate ventilation, air leakage, and aspiration, whereas a very large ETT may cause serious complications including airway damage, post-intubation croup, and, in severe cases, subglottic stenosis. Although the pediatric larynx is conical, the narrowest part, the rima glottidis, is cylindrical in the anteroposterior dimension, regardless of development, and the cricoid ring is slightly elliptical. A cuffed ETT reduces the number of endotracheal intubation attempts, and if cuff pressure can be maintained within a safe range, the risk of airway damage may not be greater than that of an ETT without cuff. The age-based formula suggested by Cole (age/4 + 4) has long been used to select the appropriate ETT size in children. Because age-based formulas in children are not always accurate, various alternative methods for estimating the ETT size have been examined and suggested. Chest radiography, ultrasound, and a three-dimensional airway model can be used to determine the appropriate ETT size; however, there are several limitations.

Keyword

Airway management; Anesthesia; Child; Endotracheal intubation; Pediatrics; Trachea

Figure

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  Fig. 1. Endotracheal tube (ETT) with cross-sectional circular shape in an elliptical-shaped airway (A) and in a circular airway (B). When placed in an elliptical airway, there may be lateral pressure on the mucosa of the trachea, and possible leakage during continuous positive airway pressure test above and below the ETT in the anterior–posterior diameter. When a cuff (violet) is inflated in the elliptical airway, the airway can be sealed with equal pressure on all aspects of the tracheal wall (C).

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  Fig. 2. Ideal position of the cuffed endotracheal tube.

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  Fig. 3. Microcuff endotracheal tube.

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  Fig. 4. ID (mm) = 3 + 0.3 × (tra­cheal diameter at at C7 from chest radiograph. C7: seventh cervical vertebra, ID: internal diameter.

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  Fig. 5. Ultrasonographic measurement of the transverse subglottic diameter of the cricoid cartilage. The cricoid cartilage appears as a round hypoechoic structure with hyperechoic edges, composed of perichondrium. The transverse subglottic diameter is determined by measuring the dimension of the air-mucosa interface (between the two white crosses) within the bilateral inner margin of the cricoid cartilage.

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  Fig. 6. (A, left) An FDM type 3D printer CreatBot (CreatBot F430, Henan Suwei Electronic Technology Co., Ltd., China) was used to print 3D airway models from the sub-glottis to the upper carina. (A, middle) 3D-printed airway model. (A, right). Cuffed ETTs is inserted into a 3D-printed airway model. (B) DICOM files of pediatric patient’s CT images were converted to STL files using the 3D conversion software open source program InVersalius (InVersalius 3.0, Renato Archer Information Technology Center, Brazil). (C) STL files were converted to G-Code 3D Printer File [49]. Adapted from the article of Park et al. (Korean J Anesthesiol 2021;74:333-41) [49]. FDM: fused deposition modeling, DICOM: Digital Imaging and Communications in Medicine, CT: computed tomography, ETT: endotracheal tube, STL: Standard Triangle Language, 3D: three-dimensional.

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