Which complication is NOT associated with endotracheal intubation?

The correct answer focuses on left main stem bronchus intubation, which is not a complication typically associated with endotracheal intubation itself but rather a potential outcome of misplacing the tube during the procedure. It occurs when the endotracheal tube is inadvertently advanced too far into the trachea, leading to unilateral ventilation of the left lung.

In contrast, pneumothorax can occur as a result of accidental injury to the pleura during the intubation process, particularly if high pressure is applied during bag mask ventilation. Esophageal intubation is a significant complication wherein the tube is mistakenly placed into the esophagus rather than the trachea, leading to inadequate ventilation and oxygenation. Airway obstruction, which can occur due to various factors such as tube kinking, secretions, or positioning issues, is also a recognized complication.

Thus, the potential for left main stem bronchus intubation represents a specific scenario related to the technique of tube placement, while the other options are broader complications directly tied to the risks involved in the intubation procedure.