The worst possible outcome of attempted endotracheal intubation is unrecognized esophageal intubation. The tube placement is confirmed by listening for air entry over both lung fields and over the epigastrium. If air entry or a "gurgling" sound is heard over the epigastrium, or there is an absence of air entry over the lung fields, the rescuer should immediately remove the ET tube and resume bag-valve-ventilation. If air entry is only heard over the right lung field, the ET tube may have been advanced too far - into the right main stem bronchus. In this circumstance, the ET tube should be withdrawn so that the 22 cm mark on the tube is at the corner of the mouth.

Note correct technique:

1. Attach bag-valve ventilator to ET tube.
2. Don stethoscope prior to first ventilation.
3. Listen over epigastrium with first ventilation.
4. Listen over both lung fields with subsequent ventilations.
5. Listen to trachea for air leaks.