Page 88 - AlertDiver_Winter2013

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Reporting System (www.
DAN.org/IncidentReport)
as a means to improve
reporting of incidents. RF3
also stressed the need for a
predive checklist to become
commonplace in recreational
and technical diving.
Current Safety Issues in
Recreational Diving
Prevention of injuries and fatalities remains a primary
concern of DAN Research. The problem is compounded
by the aging population of recreational divers, which is a
reflection of an aging general population combined with
relatively fewer young people willing to commit to diving
(many engage in diving occasionally). Explore-diving
opportunities like those popular at many resorts cater to
such occasional divers. On the other hand, some divers
engage in more challenging diving practices such as technical
diving, cave diving and breath-hold diving, which expose
them to different sets of risks. Here is an overview of our
ongoing studies and our plan for addressing these issues.
Health and Diving Practices Survey
This study indicated that DAN members are healthier
and wealthier than the general population in the U.S.
The proportion of divers with known cardiac problems is
small, but there are many who have known risk factors for
cardiac disease such as smoking, physical inactivity, obesity,
high blood cholesterol and high blood pressure. The best
strategies for mitigating the associated risks are the same
as for nondivers: adopting a healthy lifestyle; controlling
cholesterol, blood pressure and weight; and regularly
engaging in physical activity. More research is needed to
learn how diving may affect these divers and to identify those
whose risk could be increased due to diving.
Patent Foramen Ovale (PFO) and Diving
The risk of DCS may be increased in divers with a PFO. A
retrospective review of statistics indicates there may be an
association between PFO and DCS, but the risk of DCS is small
in all divers (whether or not they have a PFO). Some divers with
PFOs who suffered multiple episodes of DCS decide to quit
diving, others choose to dive more conservatively, and some
others choose to undergo a medical procedure that closes the
PFO to mitigate their risk. The procedure of closure includes a
small risk of complications, but a true risk-benefit analysis had
never been conducted. In cooperation
with Dr. Doug Ebersole of Watson
Clinic in Florida, we undertook a
five-year study to compare the safety
of divers who underwent PFO closure and those who continue
diving without it. There are currently 60 participants in the
study, and enrollment is still open.
Nitrox Versus Air in Open-Circuit Diving
Nitrox has been widely used in the past few decades. Despite
some concerns raised in the early stages of this practice, injury
and fatality statistics did not show any increase due to the use
of nitrox. There is a general consensus that replacing air with
nitrox and diving at the same depth for the same duration
provides an additional margin of safety (due to a reduced
partial pressure of nitrogen and more oxygen). However,
using nitrox to extend dive time without incurring mandatory
decompression or diving to the equivalent air depth was never
explicitly tested in recreational diving. We compared postdive
bubble grades in divers breathing air at 60 feet of seawater
with divers breathing nitrox at the equivalent depth of 70 feet.
Both depths exposed divers to the same partial pressure of
nitrogen. The overall bubble grades were similar, but the high
bubble grades and, probably, the greater risk of DCS were
more common in the divers breathing air. This small favorable
effect may have been due to the higher partial pressure of
oxygen in nitrox. While this suggests a benefit of nitrox diving,
we continue research by analyzing circulating microparticles,
small fragments shed from cells, which may be in some way
implicated as mechanisms of DCS.
Extreme Diving Field Studies
Technical divers use mixed gases in open- and closed-circuit
diving and regularly exceed depths of 200 feet. This exposes
their bodies to large loads of dissolved inert gases and imposes
significant decompression obligations. Most decompression
tables and algorithms used in dive computers have not been
systematically tested. Since an observational study during
dives on the Britannic in 2006, we have conducted monitoring
of technical divers on many occasions and in various diving
activities. The main tool in our research is echocardiography,
which enables imaging of bubbles that pass through heart. So far
Clockwise from right: Urine osmolality
(concentration) is measured with a portable
refractometer during a field dive-monitoring study.
A portable transthoracic echo (TTE) imaging device
is used to look for postdive bubbles in the heart.
A Holter monitor measures electric activity of the
heart. A DAN researcher organizes blood tubes
collected for microparticle research.
Rosemary E. Lunn
NEAL POLLOCK
NEAL POLLOCK
Marilyn Gibbs