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    Common Motion Sickness Drug Could Impair Divers' Judgment


    While in the chamber, the subjects performed various tasks of memory, verbal ability, and manual dexterity. Each person also wore a monitor that recorded his or her heart rate and rhythm. They went through the same battery of tests while resting in the chamber at normal atmospheric pressure.

    Even without the drugs, the participants exhibited increased anxiety and decreased verbal fluency at conditions simulating 66 feet under water, the researchers found. Pseudoephedrine produced a slight increase in heart rate and interacted with the depth effect to increase the decline in verbal fluency, but overall, the authors write that "it is unlikely that pseudoephedrine adds significant risk to the diver."

    Dimenhydrinate, on the other hand, was associated with much lower scores on a test that required the subjects to switch rapidly between two tasks and is a measure of mental flexibility. "We showed a definite impairment [from dimenhydrinate], especially in combination with narcosis, and the deeper you go, the greater your decline," says O'Toole, an experienced diver who directs the hyperbaric medicine program at the University of Pittsburgh. "I would not recommend that someone take this drug and dive."

    Add dimenhydrinate to the effects of narcosis "and you're really zonked," says Murray Grossan, MD, a Los Angeles-based otolaryngologist and a scuba diver since 1970. He tells WebMD that many fatal diving accidents occur because divers ignore or forget to watch the monitors that tell them they're low on air, which could be the result of impaired judgment produced by narcosis. Grossan was not involved in the study.

    However, the potential effects of pseudoephedrine on heart function should not be dismissed, warns Claes Lundgren, MD, PhD, director of the Center for Research and Education in Special Environments at the State University of New York in Buffalo. People diving at great depths may experience an immersion effect, in which blood travels away from the limbs and into the chest, where it may distend the heart and render it more vulnerable to the effects of drugs that affect heart rhythm. "This could be responsible for a number of scuba deaths that remained unexplained," he tells WebMD.

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