Cricoid and left bronchial diameter in the pediatric population

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Lung isolation in the pediatric population can be problematic. The diameter and length of the right and left mainstem bronchi are not well described in young children. Information regarding these measurements may help determine the appropriate size of endotracheal tubes for endobronchial intubation as well as the development of lung isolation devices for the pediatric population. The present study is based on computed tomography (CT) measurements to evaluate airway dimensions. The goal of this study was to define the relationship between the diameters of the left mainstem bronchus (LMSB) and the cricoid ring, and to study the effect of age, weight, and height on these dimensions.


The two-dimensional CT images of 102 children, ranging in age from 1 month to 10 years, undergoing radiological evaluation unrelated to airway symptomatology were examined. The cricoid dimensions (anteroposterior and transverse diameters) were measured using transverse plane images. The LMSB diameter was measured below the carina along the long axis of left main bronchus. Univariate regression analysis was used to determine whether one or more of the variables (age, gender, height, weight) had a predictable relationship with the cricoid and the LMSB diameters.


The cricoid as well as the LMSB diameters increase with age, height, and weight. The relationship between the cricoid diameter and the LMSB diameter remains constant across all ages with a ratio of 0.78 ± 0.14. This ratio was slightly larger for girls than boys (0.81 ± 0.16 vs 0.77 ± 0.13).


The cricoid to LMSB ratio (relationship) remains constant with respect to age, height, and weight.

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