Which airway device should not be used on conscious patients due to tolerance issues?

The oropharyngeal airway is not suitable for use on conscious patients primarily because it can provoke a gag reflex. This reflex is a natural response that occurs when objects are placed in the back of the throat, which is where the oropharyngeal airway is positioned. In conscious individuals, this gagging sensation can cause significant discomfort and anxiety, making it difficult for them to tolerate the device.

In contrast, other devices, like the endotracheal tube, are typically used in situations where the patient is unconscious or heavily sedated. The nasopharyngeal airway can be used on conscious patients because it is less likely to induce a gag reflex, as it is inserted through the nasal passage. The supraglottic airway device is also designed for use in unconscious or sedated patients but may be tolerable for some conscious individuals under certain conditions. Thus, the oropharyngeal airway stands out as the choice that should not be used on conscious patients due to the issue of tolerance related to the gag reflex.