An endotracheal tube is a thin, flexible tube placed into a person's windpipe (trachea) to help them breathe. It's often used during surgery or for people who can't breathe on their own. The tube can be inserted through the mouth (orotracheal) or nose (nasotracheal). It may have a balloon at the tip to create a seal and prevent air leaks. Endotracheal tubes help deliver oxygen and keep airways open.