www.alertdiver.com
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39
physics as well as your physiology. As gas density goes up with
increasing depth, carbon dioxide (CO
2
) retention also goes up
with increased effort or work at depth. With an increase in
CO
2
retention, your likelihood of passing out from hypercapnia
(excess CO
2
) or a seizure also increases. (Excess CO
2
can
predispose divers to seizures when using any gas mixture with
a high partial pressure of oxygen.) Overexertion at depth has
killed many divers via both mechanisms and is something to be
avoided at all costs. A highly skilled diver will expend far less
effort to move through the water than a brand new but highly
fit diver. The best scenario: Be both experienced and in good
physical shape with properly streamlined equipment.
Speaking of overexertion, recent research indicates diver
mortality from cardiac events is a growing concern, and
various means of addressing this concern were the subject
of heated debates at the 2010 DAN
®
Recreational Diving
Fatalities Workshop. Overall fitness should not be taken
lightly; if you are concerned about your cardiac health, talk
to your doctor, or call DAN for a referral to a doctor trained
in dive medicine. If you are over 40 or have cardiac risk
factors such as long-standing high blood pressure, a history
of tobacco use, heart disease in the family, diabetes or other
medical conditions, you can’t go wrong getting evaluated.
THE HAZARDS OF WRECKS
OK, you work out regularly, don’t smoke, keep up with your
health concerns, have streamlined your gear so an occasional
fin stroke keeps you ahead of the divemaster and have logged
82 Caribbean and offshore dives in the last three years. So what
do you need to be concerned about down on a wreck?
Wrecks present unique hazards for those diving the outside
as well as the inside of the structure. The outside of a wreck
seems deceptively safe. The reality is that fishermen love
wrecks as much as we do, only they seem determined to cover
L u x u r y L i v e a b o a r d
T u b b aTa h a
b o h o L
S o u T h e r n L e y T e
a n i L a o
Puerto
G
alera
Dumaguete
a p o r e e f
visit us at deMa - booth #1572
Explore the Philippines
in style ...with Atlantis
at l a n t i s ho t e l . com
Nippo Maru bridge,
Truk Lagoon
38-40_Advanced_Diving_Fall2011.indd 39
9/29/11