Measurement of tracheal length on chest radiographs by using the picture archiving communication system. The distance between the vocal cords (△) and carina tracheae was defined as the tracheal length. This sample patient was 7 days old, 51 cm tall, and weighed 3.1 kg, undergoing arterial switch surgery for transposition of the great arteries. The tracheal length was measured as 41.3 cm, which corresponded to 8.1% of the body height.