Endotracheal intubation has many advantage such as airway protection, maintenance of patent airway, pulmonary toilet, application of positive pressure ventilation, and maintenance of adequate oxygenation. But risks that develop complications related to endotracheal tube always present, when we insert a tube into the trachea. We have experienced an armored tube obstruction with bulged inner wall after EO gas sterilization. So, it is important that we have to pretest a tube and check pateney of the inside of a tube, before endotracheal intubation.