In underwater diving, Alternobaric vertigo is dizziness resulting from unequal pressures being exerted between the ears due to one or the other Eustachian tubes being less patent than the other. This might have occurred due to barotrauma of descent and/or the effects of nasal decongestants. It is due to unequal increase in middle ear pressures on ascent, is usually mild, and most often cleared by further ascent.