To determine the correct size of endotracheal tubes (ETT) for endotracheal intubation of pediatric patients is no menial task. Although new methods have been investigated to determine ETT size, and the three-dimensional (3D) printing technology has been successful in the field of surgery, there are not many studies in the field of anesthesia. The purpose of this study is to evaluate the accuracy of a 3D airway model for prediction of the correct ETT size, and compare the results with a conventional age-based formula in pediatric patients.

To determine the correct size of endotracheal tubes (ETT) for endotracheal intubation of pediatric patients is no menial task. Although new methods have been investigated to determine ETT size, and the three-dimensional (3D) printing technology has been successful in the field of surgery, there are not many studies in the field of anesthesia. The purpose of this study is to evaluate the accuracy of a 3D airway model for prediction of the correct ETT size, and compare the results with a conventional age-based formula in pediatric patients. : Thirty five pediatric patients under 6 years of age who were scheduled for congenital heart surgery. In the pre-anaesthetic period, the patient's computed tomography (CT) images were converted to STL files using the 3D conversion program. An FDM type 3D printer was used to print 3D airway models from the sub-glottis to the upper carina. ETT size was selected by inserting various sized cuffed-ETTs to a printed 3D airway model.

Inclusion Criteria:

• children under 6 years of age (range 4 days to 61 months) scheduled for surgery for congenital heart disease with chest computed tomography (CT) images including upper airways

Exclusion Criteria:

• pediatric patients with intubation or tracheostomy before general anesthesia due to underlying disease
• small sized airway with inner diameter <3.0 mm because of pre-term or low birth weight
• unstable vital signs during induction
• history of difficult intubation
• emergency surgery where printing a 3D airway model in advance was not possible

We enrolled children under 6 years of age (range 4 days to 61 months) scheduled for surgery for congenital heart disease with chest computed tomography (CT) images including upper airways from September 3, 2019, to March, 16, 2020. Pediatric patients with congenital heart disease were chosen because they usually keep their ETT with mechanical ventilation in the intensive care unit and also have relatively high risk of complication associated with ETT comparing to healthy patients. Therefore, we think it is more important to select appropriate size of ETT in pediatric patients with congenital heart disease.