<prompt> What should be the internal diameter of the endotracheal tube in a child weighing 1500 gm ?2 mm2.5 mm3 mm3.5 mm  <response>: Body weight in grams and internal diameter of ET tube :- 1000 gm 2.5 mm, 1000-2000 gm 3 mm, 2000-3000 3.5 mm, 3000 3.5-4.0 mm. 