Disorientation and Vertigo
Under certain conditions, a diver may develop underwater vertigo. This condition is not to be confused with dizziness or lightheadedness. It is an actual severe disorientation that is experienced as a sensation that either the diver or the sea is spinning around without reference. The condition may become immediately life threatening if not recognized and dealt with appropriately. Conditions that may lead to vertigo include visual sensory deprivation, disorders of the ear, or inhaled gas problems such as hypoxia (low oxygen) or hypocapnia (low carbon dioxide).
The body uses three sensory input systems to establish orientation in space. If any two are rendered ineffective then severe disorientation/vertigo may ensue. The three components are the nervous system, the inner ear, and the eyes. The inner ear contains a network of air and fluid levels that provide gravity-related clues to spatial orientation. The peripheral nerves and brain work together to use touch, weight, and solid ground to determine orientation. The eyes provide visual input. Underwater the sensation of “touching” your environment is all around you so the nervous system remains relatively clueless to spatial orientation. As aforementioned, the inner ear primarily uses gravity for its sensory input. The inner ear is therefore the only system that determines orientation in space without clues from the environment.
Visual sensory deprivation may occur at night or when diving in very murky water. It will typically occur with inexperienced divers who are not skilled at using alternative underwater visual or sensory clues. A diver may use a floating gauge or camera or floating bubbles to determine which way is up. A weight belt will pull in a downward direction giving the nervous system orientation input. A chest filled with air will float upward with heavy legs below. Nevertheless, if a diver is unable to use alternative visual or sensory clues to determine orientation, disorientation may ensue. Hyperventilation, anxiety, and eventually panic often follow. Severe vertigo is often the result. If such severe disorientation is experienced it may accelerate into a life-threatening situation.
Disorders of the ear may cause disorientation. As previously mentioned, two of the three balancing systems of the body must be working to maintain normal spatial orientation. Disorders that affect the balancing mechanisms of the inner ear may therefore lead to vertigo. Barotrauma of the middle, external, or inner ear may lead to vertigo The vestibular nerve, which sends sensory information to the brain from the middle ear, is also sensitive to hot/cold differences between the ears. Diving horizontally into relatively cold water with one external ear canal plugged and the other open may lead to disorientation and vertigo. This “caloric” vertigo resolves when the diver resumes a vertical position in the water.
Abnormalities to the gas supply underwater may lead to severe disorientation. These would include nitrogen narcosis, hypoxia, oxygen toxicity, or carbon dioxide toxicity.
Underwater vertigo must be followed by immediate ascent. Often a diving buddy is the only support capable of providing direction to which way is up. Because the victim may be in panic mode with severe nausea, possible vomiting or water swallowing, the buddy diver may have a very difficult time. Firmness is essential. Staged decompression stops are not followed on ascent and therefore possible decompression illness must be evaluated at the surface.
