Final answer:
An endotracheal tube placed too deeply is likely to end up in one of the primary bronchi, typically the right one due to its more vertical alignment and larger size, which can cause unilateral lung ventilation and potential injury.
Step-by-step explanation:
If an endotracheal tube is placed too far, it is most likely to end up in one of the primary bronchi. During the process of intubation, the tube is designed to pass through the larynx into the trachea and should terminate above the bifurcation where the trachea divides into the right and left primary bronchi.
However, the right primary bronchus is more vertically aligned and wider than the left, making it more likely for an endotracheal tube to mistakenly enter here if inserted too deeply.
This can lead to a situation where only one lung is ventilated, which could cause inadequate oxygenation and potential lung injury due to overinflation. Medical professionals are trained to assess proper placement by checking for bilateral breath sounds and monitoring end-tidal CO2 levels, among other things, to ensure the tube is correctly positioned within the trachea.
Chest x-rays can also confirm proper placement. Thus, careful placement and confirmation of the endotracheal tube's position are critical to avoid such complications.