What effect does a forceful Valsalva maneuver during descent have?

A forceful Valsalva maneuver, which involves exhaling forcefully against a closed airway, primarily serves to equalize pressure in the middle ear with the surrounding water pressure during descent. This maneuver helps prevent discomfort and potential injury due to sudden changes in pressure. While some divers might experience alternobaric vertigo due to unequal pressure changes between the ears, the main purpose and result of a successful Valsalva is achieving equalization of pressure.

Although the maneuver may help alleviate ear pressure temporarily, it does not prevent barotrauma if the pressure is not properly equalized. Therefore, the key aspect of the Valsalva maneuver is its role in equalizing pressure effectively, making it an essential technique for divers to practice to maintain ear health during descent and ascent in underwater environments.