PURPOSE: The application of ultrasound in the intubation of endotracheal tube (ETT) was reported recently, but these studies mainly focused on whether the ETT was inserted in the airway rather than in the esophagus. For respiratoryintensive care unit (RICU) patients, the ETT should not only be placed in the trachea, but also be located in a rational distance (2-5cm) from carina. One of the most usefulconfirmation methods isfiber bronchoscope, but the technique is expensive and invasive. Howeverthe technique of ultrasound is inexpensive and non-invasive. We hypothesize that bedside ultrasound would become a new powerful tool in confirmation the location of the ETT.