Establishment of a CT-based prediction model for endotracheal tube size in infants aged <1 year

By quantifying airway parameters on computed tomography (CT) and incorporating clinical factors such as age and prematurity, this study developed an airway prediction model for infants to provide more accurate guidance for endotracheal tube size selection and insertion depth in patients under one year of age.

A retrospective analysis of data on infants under one year of age who underwent preoperative anesthesia evaluation at Peking University People's Hospital from January 2020 to December 2022. Inclusion criteria: All enrolled infants underwent chest CT examination, with the scanning range covering the level of the cricoid cartilage. The development of cricoid cartilage was associated with laryngeal cartilage maturity. Its size and ossification degree change with age, sex, height and other factors. Therefore, we collected clinical data including the age, sex, gestational age, preterm birth, height and weight at birth and visit which may affect the shortest diameter of the cricoid cartilage in children. Infants with congenital laryngeal malformations, acquired nutritional deficiencies, hormonal abnormalities such as hypothyroidism, neck tumors and a history of maternal smoking during pregnancy were excluded. Accurately measure the shortest inner diameter of the cricoid cartilage and the distance from the cricoid cartilage to the carina on CT images. SPSS 24.0 software was used for simple and multiple linear regression analysis to screen key factors. Corresponding prediction models were established for the shortest cricoid cartilage diameter and the cricoid-to-carina distance, so as to facilitate the individualized selection of tracheal tube sizes and insertion depths in clinical practice.

In this study, age and preterm birth were identified as independent influencing factors for the shortest cricoid cartilage diameter in infants [P = 0.008, 0.005(95% CI: 0.001 to 0.008); P = 0.022, -1.261 (95% CI: -2.321 to -0.201)]. The established prediction formulas were as follows: the shortest diameter of the cricoid cartilage in full-term infants (mm) = 6.119 + 0.005 × age; The shortest diameter of the cricoid cartilage in preterm infants (mm) = 6.119 + 0.005 × age-1.261. For the distance from the cricoid cartilage to the carina, age was the only significant influencing factor [P = 0.003, 35.725(95% CI: 0.016 to 0.073)], and carina formula was derived as follows: distance from the cricoid cartilage to the carina (mm) = 35.725 + 0.044 × age.

Age and preterm status were independently associated with the shortest cricoid cartilage diameter in infants under one year of age, suggesting that preterm infants may require smaller endotracheal tubes than full-term infants of the same age. Age was also associated with the cricoid-to-carina distance. These CT-based findings may support more individualized airway management in infants. However, despite internal bootstrap validation, the model remains limited by the lack of external validation, small sample size, and highly specific ophthalmologic surgical population; therefore, broader validation is required before clinical generalization.