W
hen it comes to
safety we each
have our own
ideas about what
constitutes acceptable risk. For
some divers it means diving within
recreational limits, while for others
it means seeking various types of
advanced training to dive beyond
those limits. As your dive safety
association, we work hard to provide
you with the information you need
to be a prepared diver and to make
informed decisions about the level of
risk you wish to accept.
On a recent dive trip, someone
asked me about the rationale behind
DAN’s Flying After Diving Guidelines and questioned
whether they were too conservative.
A 2013 study of commercial aircraft flights found an
average peak cabin altitude of approximately 6,300 feet
with 10 percent exceeding 8,000 feet, the cabin altitude
widely accepted as the normal maximum. Without a
sufficient surface interval between a diver’s last dive
and his flight, the change in atmospheric pressure from
sea level to these altitudes can be sufficient to cause
symptoms of decompression sickness (DCS). It’s also
important to note that flying may involve situations that
increase the risk, such as an unexpected loss of cabin
pressure or diversions mandated by weather or air-traffic
control that lead to an increase in cabin altitude.
For more than two decades DAN has been investigating
preflight surface intervals after diving. Through
experimental studies, workshops and years of analysis,
the DAN research team has worked diligently to establish
meaningful safety guidelines for divers.
Leaders in the diving research community held
a workshop in 1989 to discuss flying-after-diving
guidelines. The recommendations from that meeting
were a 12-hour interval after a single, no-decompression
dive; a 24-hour wait after multiday, no-decompression
diving; greater than 24 hours after dives with
decompression obligations; and no flying for divers
exhibiting symptoms of DCS unless a transfer by air
ambulance was required to reach medical care.
Since these discussions, DAN has
worked with key stakeholders including
the Professional Association of Diving
Instructors (PADI), the U.S. Navy
and the Duke Center for Hyperbaric
Medicine and Environmental
Physiology to investigate and calibrate
these guidelines. In 2002 DAN
sponsored the Flying After Recreational
Diving Workshop, where participants
determined that the guidelines should
be revised based on experimental data
gathered from a series of DAN-funded
dry hyperbaric studies at Duke.
While many dive resorts and
livaboards recommend a 24-hour
interval between diving and flying, the
guidelines for recreational diving that were established
after this workshop are the ones we follow today. The
recommended minimum preflight surface intervals are:
• 12 hours following a single no-decompression dive
• 18 hours after multiple dives or multiple days of diving
• Substantially greater than 18 hours for technical dives
requiring decompression stops
Since these guidelines were established, DAN has
continued to conduct chamber studies to validate
and calibrate the original findings. The most recent
series of studies compared the protocols of dry, resting
divers; dry, exercising divers; and immersed, exercising
divers. While the data are still being analyzed,
preliminary findings suggest there is no difference in
DCS risk between the previously established dry-tested
guidelines (thus validating the previous data set).
In modern diving, our computers use algorithms to predict
when flying is deemed safe, but algorithms vary among
computers, and it’s prudent to err toward the conservative.
It’s important to remember that the established
flying-after-diving guidelines have been tested and
offer the best guidance available for building in a
safety buffer during your travels. We are confident
in these findings, and we will continue our research
efforts to help you make informed decisions about
your safety. To learn more, I encourage you to visit
DAN.org/Research or email our team directly at
.
AD
FROM THE SAFETY STOP
//
P E R S P E C T I V E S
8
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SPRING 2014
Flying After Diving
B y B i l l Z i e f l e
STEVE EXUM
