Final answer:
For a client with Ménière's disease experiencing vertigo, the best nursing intervention is to turn off the television and darken the room, as this helps reduce stimuli that could worsen symptoms.
Step-by-step explanation:
The intervention a nurse should implement for a client with Ménière's disease who is experiencing vertigo and is incapacitated is D) Turn off the television and darken the room. This action helps reduce stimuli that can aggravate vertigo symptoms. Other interventions such as keeping the head of the bed elevated can provide comfort, but in the acute phase of vertigo, limiting sensory input is most beneficial. Encouraging high fluid intake isn't necessarily helpful during an acute vertigo attack, and changing positions frequently can potentially worsen vertigo symptoms. The primary care for this condition should be aimed at minimizing the factors that can lead to increased vertigo.