What sensation may indicate nitrogen narcosis?

The sensation that may indicate nitrogen narcosis is tingling and vague numbness of the lips, gums, and legs. Nitrogen narcosis, often referred to as the "rapture of the deep," occurs when divers are exposed to increased partial pressures of nitrogen at depths typically greater than 30 meters (approximately 100 feet). The increased pressure can alter the way nitrogen affects the central nervous system, leading to various neurological effects.

Tingling and numbness in specific areas, such as the lips, gums, and legs, can be symptoms experienced due to the psychoactive effects of nitrogen under high-pressure conditions. These sensations can signal that a diver is becoming impaired and may need to ascend to a shallower depth to relieve the symptoms. Understanding these sensations is crucial for divers, as recognizing them can help prevent more severe effects of narcosis, such as impaired judgment and motor skills.

Other options present different types of sensations or symptoms that do not relate directly to nitrogen narcosis. For instance, sudden blindness and high-pitched hearing are not typical indicators of this condition. Numbness in the extremities might suggest other issues unrelated to narcosis, making the understanding of the appropriate sensation critical for safety in diving.