Endotracheal tube in the esophagus is best assessed by:
Chest wall movement
Auscultation
CO2 Exhalation
Chest tube passes through vocal cords
For sure shot confirmation of endotracheal tube Capnography is used. ET tube in trachea (capnography) While if almost Flat line appears - Et tube is in esophagus.
FMGE 2019