In which situation is the use of a nasopharyngeal airway contraindicated?

The use of a nasopharyngeal airway is contraindicated in patients with a head injury primarily due to the risk of further injury or complication. In cases of significant head trauma, particularly if there is suspicion of a skull fracture, inserting a nasopharyngeal airway can cause the device to penetrate through the fractured skull or into the brain tissue, leading to severe complications such as intracranial hemorrhage or meningitis.

In contrast, the other scenarios do not present the same level of risk. A conscious patient might still require airway management; an airway adjunct could be appropriate as long as their gag reflex is intact and they can protect their airway. Patients with loud snoring without obstruction may indicate a need for airway support but are not contraindicated. Regarding patients with a history of nasal surgery, it might be necessary to exercise caution, but this does not automatically preclude the use of a nasopharyngeal airway, which might still be appropriate depending on the specific circumstances.