The optimal position for an endotracheal tube is with the tip 3-7 cm above the carina.

The optimal position for a nasogastric tube is with the tip (and side hole) in the stomach well below the diaphragm, at least 10 cm beyond the gastro-esophageal junction.

The optimal position for an internal jugular central venous catheter is with the tip in the superior vena cava or at the superior cavo-atrial junction.