Page 50 - AlertDiver_Winter2013
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at Duke University conducted an animal study and demonstrated that
rats treated with PDE-5 seized sooner than untreated animals. The
lesson for divers is that use of PDE-5 inhibitors the night before diving
may not be safe. Attention should be given to the effective duration
of the chosen medication and the partial pressures of oxygen likely to
be encountered on planned dives. The diver should discuss dive plans
with a DAN medic or a doctor trained in dive medicine.
In the case of pseudoephedrine, things evolved differently. Several
divers who experienced symptoms of oxygen toxicity called DAN and
blamed the drug pseudoephedrine, an active ingredient in many over-
the-counter medications (such as Sudafed®) used to treat congestion.
DAN contracted an animal study with the University of South Florida.
The study indicated that normal doses of pseudoephedrine should
not increase the risk of seizures in the majority of divers, but there
was a huge individual variability in susceptibility to oxygen toxicity
— sufficient variability to explain why divers sometimes get toxicity
symptoms despite “safe” exposures. It was also demonstrated that very
large doses, which may be achieved if a diver uses multiple over-the-
counter drugs containing pseudoephedrine, may increase susceptibility
to oxygen toxicity.
Protection from Oxygen Toxicity
So far there are no drugs that would practically increase tolerance
to oxygen, but these may be developed in the future. There were
hopes that some antioxidants such as vitamin E and vitamin C could
protect against oxygen toxicity. While this may be true in animals
with a lack of these vitamins, in normally fed animals no beneficial
effect of vitamin supplementation has been demonstrated. On the
other hand, there are many drugs that may increase susceptibility to
oxygen toxicity such as reserpine, quanethidine, thyroxin, disulfiram
and others. Divers taking medications for chronic conditions should
consult their physicians before getting involved with nitrox or mixed-
gas diving.
The best protection is to keep inspired oxygen pressure at or below
1.2 ATA while physically active and at or below 1.6 ATA during
decompression. In addition, use low-oxygen breaks, control carbon
dioxide, do not overexert yourself, stay warm, and be fit and healthy.
Divers wishing to further reduce the risk of drowning due to seizure might
consider using a full face mask and should never dive alone.
AD
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WINTER 2013
ABOUT THE AUTHOR
Petar Denoble, M.D., D.Sc.,
is the senior director of DAN Research. After
graduating from medical school, he joined the navy in the former Yugoslavia and
specialized in naval and diving medicine. For 13 years he was involved with training,
supervision and treatment of divers in open-circuit, closed-circuit, deep-bounce and
saturation diving. His doctoral thesis focused on studying oxygen consumption in
underwater swimming. Denoble has been at DAN for 20 years and has been involved
in the development of the largest database of exposure and outcomes in recreational
diving, the monitoring of diving injuries and the study, treatment and prevention of fatal
outcomes and long-term consequences of diving accidents.
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