The development of the cricoid cartilage and its implications for the use of endotracheal tubes in the pediatric population

Abstract

BackgroundThe rigid cricoid cartilage is functionally the narrowest portion of the larynx. There is some controversy over the shape of the pediatric cricoid cartilage in the transverse plane. It is important to understand the development of the cricoid cartilage so that endo‐traceheal tubes can be used more safely.AimTo determine changes in the internal diameter and shape of the cricoid cartilage during development and explore the implications of those changes for the selection of ETT type and size for children.MethodsThe cervical computed tomography scans were reviewed in patients aged 1‐20 years. After performing the multiplanar reconstruction and correcting the slant, the transverse and anteroposterior internal diameters of the inlet and outlet of the cricoid cartilage were measured, respectively. The angle between the arch and the lamina of the cricoid cartilage in the middle sagittal plane was measured. The ratios of transverse to anteroposterior diameter for the inlet and outlet of the cricoid cartilage were calculated, respectively.ResultsIn females, the internal diameters of the cricoid cartilage increased linearly with age. In males, the internal diameters of the cricoid cartilage exhibited a growth spurt during adolescence. The transverse diameter of the inlet was the smallest diameter of the cricoid cartilage, and the predicting formula of the transverse diameter of the inlet for children aged 1‐12 was 0.4 × age (year) + 5.1, R2 = .758. The angle between the arch and lamina of the cricoid cartilage and the ratios of transverse to anteroposterior diameter correlated weakly with age.ConclusionThe transverse inner diameter of the inlet is the smallest diameter of the cricoid cartilage. The “funnel shape” of the cricoid cartilage remains unchanged during development. The outer diameter should be considered when selecting an endotracheal tube.

Age-related Change of the Dimensions of the Cricoid Cartilage in Adults

“…12,13 However, one previous in vivo study has shown that the cricoid cartilage remains “funnel-shaped” in the middle sagittal plane during development, and the transition to “column-shaped” does not occur. 7 In this study, we found that the cricoid cartilage is still “funnel-shaped” in the adult population and the cricoid angle does not change with age. In addition, the average cricoid angle is greater in males than in females, showing that the cricoid cartilage is more “funnel-shaped” in males.…”

“…Computed tomography is a reliable tool to measure the diameters of the airway and it has been successfully used to measure the diameter of the cricoid cartilage in the pediatric population. 7,[9][10][11] After performing the multiplanar reconstruction of the cervical CT scans and correcting the slant, we can easily obtain the slice of the inlet and outlet of the cricoid cartilage. Then the diameters of the cricoid cartilage can be accurately measured.…”

“…This is consistent with previous studies and the classic textbooks. 1,7 The shape of the outlet of the cricoid cartilage, however, varies greatly among individuals and it is related with age and sex. In subjects aged 50 or younger, the cricoid outlets were mostly round or vertical oval in both genders, while the transverse oval was a minority.…”

“…1 Previous studies have shown that the shapes of the cricoid outlet are similar between different genders at the end of puberty. 7 However, there are significant gender differences in the shapes of the cricoid outlet among the elderly. 8 It is not clear when the sexual dimorphism in the shape of the cricoid cartilage occurs.…”

Dimensional compatibility of rigid ventilating bronchoscopes with pediatric airway anatomy using different recommendations for age‐related sizing—A bench study

“…The following anatomical airway data were used to assess age‐related dimensional compatibility of the pediatric rigid bronchoscopes: anterior‐posterior and lateral internal diameters of the cricoid outlet, of the mid‐trachea, of the proximal left and right mainstem bronchus as well as the length of the trachea (vocal cords to carina distance). Anatomical data for the cricoid were taken from the work published by Liu et al, 17 who recently reported on internal cricoid diameters assessed by cervical computed tomography in 625 patients aged from 1 to 20 years. Data on tracheal and bronchial dimensions were obtained from Szelloe et al 18 This work assessed lower airway dimensions based on computer tomography chest scans obtained from 195 pediatric patients aged from 0.04 to 16.0 years.…”