I sometimes see divers on the boat who get dizzy after they ascend. Some become distressed by the phenomenon and then ask the question "Am I bent" or "Is this a sign of decompression illness?"
After a quick inspection, I generally give them a reassuring YES and NO! But, if the pain persists, you become disorientated, collapse and the dizziness doesn't go away, see your doctor immediately.
The diver is suffering from vertigo.
A sensation of whirling and loss of balance, associated particularly with looking down from a great height, or caused by disease affecting the inner ear or the vestibular nerve; giddiness.
Synonyms: dizziness, giddiness, light-headedness, loss of balance, loss of equilibrium, spinning/swimming of the head;
Symptoms of Vertigo are usually more pronounced, whilst a diver is ascending. Not only are the symptoms uncomfortable, but they also can lead to catastrophic problems for the diver. There is the very real sensation, that the world around them is moving, spinning, tilting, all whilst they are standing or sitting still.
Vertigo is the sensation that the room is spinning, and is a form of dizziness. Divers generally feel off-balance, feel like they are about pass out or at the least very light headed and need to sit down, before they fall down. Being on a rocking boat, certainly doesn't help the nausea sensation.
What the diver is experiencing is called "Alternobaric Vertigo", which is caused by unequal pressures between your middle-ear compartments. Experiencing vertigo whilst ascending is fairly typical, but not really that common, amongst scuba divers.
To explain this further- the body maintains balance with sensory information from three systems, proprioception, vision and the vestibular system. Sensory input from these three systems is integrated and processed within the brain. The brain responds with stimuli that are sent to the eyes to help maintain steady vision and to the muscles, to help maintain balance and posture.
Vertigo in divers is brought about by divers having a slight cold, deciding to dive even though they must equalise with a little bit of difficulty or may opt to use sinus medications, to ease the equalising process- they continue to descend, even whilst having difficulty with the equalisation process- After a short time underwater, the medications wear off or the slight blockage now becomes evident, only noticing as the diver begins their ascent. Upon noticing the sensation of giddiness, the diver grabs the ascent line, slows down their ascent and begins the process of descending and ascending along the ascent line to clear the blockage.
Diver stress can at this point in time, trigger or worsen vertigo, associated by becoming anxious, not equalising correctly, making a rapid ascent. The pain in the ear space is very intense and the diver complains of ear pain and nausea upon ascent. Soon after ascent, the diver continues experiencing severe dizziness and probably collapses onto the boat deck.
This diver is diagnosed as suffering DCS, put on 100% Oxygen and transported to chamber where they are treated for DCI. After several hours’ treatment in the chamber, diver does not display any DCI symptoms and is cleared by medical staff to go home.
This is where my answer Yes- Vertigo can be explained as DCS.
Do they have nitrogen bubbles in their system? No! But they do have damage to vestibular organs by barotrauma or acoustic shock, which may be permanent and are warned against diving for a period of around six to eight weeks but, if diving is not a particularly engrossed sport, most people who have experienced severe vertigom, don't dive again!
Return to diving after inner-ear barotrauma or DCS should be evaluated on an individual basis depending on the extent of permanent injury of inner-ear organs. Prevention of vertigo during dives requires careful, gradual and continuous equalisation of the pressures within the middle ear throughout the dive.
When attempting to dive with a cold, no medications should be used.
If you cannot equalise, you should abort the dive and return to the surface, slowly.
During cooler months wearing a hood- leave the hood down until you reach the bottom or, allow some water to penetrate the hood especially around the ears, to allow equalisation.