Endotracheal intubation is the insertion of a soft rubber or plastic tube (endotracheal, or ET, tube) through the nose or mouth into the windpipe (trachea). It is done to deliver oxygen or inhaled anesthetics into the lungs.
Intubation frequently is used with general anesthesia to help control breathing during surgery. It also may provide assistance (mechanical ventilation) to persons who are having difficulty breathing on their own.
WebMD Medical Reference from Healthwise