For insertion depth, the tube should be inserted such that the 5.5 - to 6.5-cm mark is at the lip for infants who weigh < 1 kg 7-cm mark for 1 kg 8-cm mark for 2 kg 9-cm mark for 3 kg The tip of the endotracheal tube should be positioned about halfway between the clavicles and the carina on chest x-ray, coinciding roughly with vertebral level T2.