DCS results from the accumulation of nitrogen bubbles in tissue and blood. Symptoms usually occur within 12 hours of diving. DCS is divided into 2 groups: type I (pain only), in which DCS causes limb or joint pain with skin or lymphatic involvement; and type II, which also includes neurologic symptoms ranging from weakness to vertigo to altered mental status. DCS II also can manifest as pulmonary symptoms, referred to as the chokes. Nitrogen narcosis describes the intoxicating effect that nitrogen has on divers. Inner ear barotrauma results from a pressure differential between the inner ear and middle ear causing a rupture of the vestibular or cochlear window. Inner ear barotrauma usually occurs close to the surface during a difficult descent. Symptoms include a sudden onset of severe vertigo not relieved by ascent, tinnitus, nystagmus, a feeling of fullness in the affected ear, and hearing loss. Arterial gas embolism is the most serious and fatal of all diving accidents. Symptoms occur on ascent, usually within 10 minutes of surfacing, and include visual disturbances, muscular or sensory disturbances, loss of consciousness, cardiac dysrhythmia, and cardiac arrest. Sudden loss of consciousness in a diver is assumed to be arterial gas embolism until proven otherwise.
- Type II decompression sickness (DCS II).
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