During descent, compressed gases cause a negative pressure on the walls
of the body cavities, such as the middle ear and the sinuses. This can
lead to pain and conductive hearing loss, rupture of the tympanic
membrane, vertigo, sinus pain, and epistaxis.2 On ascent,
these gases expand in response to decreasing barometric pressure.
When the ascent from diving is rapid, there is insufficient time for
nitrogen to reequilibrate between the tissues and the blood. This
causes the formation of nitrogen bubbles in the blood, which can be
very extensive and result in fatal gas embolism.