A syringe that is attached to the endotracheal tube immediately after an intubation attempt. If aspiration is difficult or stomach contents are withdrawn, or both, the endotracheal (ET) tube may have been placed in the esophagus and needs to be removed and reinserted. If aspiration is easy and free of stomach contents, there is a good chance that the ET tube is located in the trachea; the rescuer should then confirm tube placement by other techniques (e.g., a combination of auscultation, x-ray, and pulse oximetry).