I would use one to secure an open airway.
"When a patient becomes unconscious, the muscles in the jaw commonly relax and can allow the tongue to slide back and obstruct the airway."

"Where an artificial form of airway maintenance is necessary but it is impossible or unadvisory to use an oropharyngeal airway, the preferred type of airway adjunct. For example, in a patient having epileptic seizures whose teeth are clenched shut.
Also, oropharyngeal airways often trigger a patient's gag reflex, while nasopharyngeal airways often do not."