The combination of dive computers
and live-aboard dive
vessels encourage multiday, multidive
trips — and decompression
sickness. In addition, taking a
flight home soon after the dive trip
multiplies the chance of problems.
Here are two important pieces to
consider for your multiday diving.
In the first, Steve Goble (Senior
Hyperbaric Technician at the Royal
Adelaide Hospital, Australia) and
Dr. Lindsay Barker (with the
Hospital’s Hyperbaric Medicine
Unit) discuss the problems of
putting deeper dives between shallower
dives and taking deeper dives
at the end, rather than the beginning,
of the trip.
In the second, Aussie physician
Geoff Gordon says the way we
manage our safety stops may not be
enough and, in fact, we need to
rethink the way we go about diving.
Both pieces are versions of articles
that appeared in the Journal of the
South Pacific Medicine Society, which
we offer with their permission.
* * * *
Australian physicians studied 185
cases of DCI, sixty-two of which
were related to multiday diving.
While the mean was only six dives
in four days, the ranges were 4-30
dives in 2-21 days. For example,
one diver logged thirty dives over
eight days to 100 feet, another
dived as deep as 200 feet, 2-3 times
a day for six days. And, another
made five dives in three days, the
last thirty-seven minutes at 100 feet,
then flew home a few hours later.
Most of the divers noted at least
two major symptoms; joint
pain, headache and excessive
fatigue. Typically, the symptoms
appeared about thirteen hours
after the last dive, but in some
cases didn’t appear for four days.
The average delay between onset
and treatment was about 100
hours. Some symptoms went unnoticed
or were ignored: skin tingling,
numbness, problems with
memory and thinking, and itching.
Many patients were content to
suffer from these “vague” symptoms
for several days before realizing
that they might have a problem
and seek treatment.
When comparing multiday with
single-day divers, the symptoms differed
little. However, the singleday
group noticed their symptoms
on average six hours earlier than
their multiday counterparts, and
reported for treatment an average
of thirty- nine hours earlier. About
double the proportion of multiday
divers used computers and about
double the proportion (32
percent) took a flight after their
last dive. Most of these did so
within thirty- six hours and noted
the appearance of symptoms while
flying home.
The most common problem
appears to be making deep dives between shallow dives. It was
common to see the first dive to 60
feet, a second to 100 feet, and the
third to 70 feet, for example.
While computers calculate these
types of profiles, doing your deep
dive first and then doing progressively
shallower dives reduces your
risk.
Many live-aboard operations
face the dilemma of whether to
put deeper dives at the beginning
or the end of the trip. If the
deeper dives are at the end of a
trip then the infrequent diver has a
few days to polish up skills before
moving on to deeper diving.
However by diving deeper at the
end of a trip, the diver is then at
greater risk of DCI if he intends
flying home within 24-36 hours.
A newly qualified diver or an
infrequent club diver would
probably be at a higher risk of DCI
when participating in intense multiday
diving trips. Just the increase
in physical exercise and associated
fatigue is likely to increase risk.
Finally, divers need to realize
that vague symptoms -- fatigue,
itching, memory problems, etc. --
indicate a neurological problem
that needs treatment immediately,
not three days down the track.
* * * *
Our thinking regarding how we
dive needs to change if we are to
reduce the incidence of DCI in
recreational diving.
The holy grail of no-stop diving
may not be such a laudable goal
after all. The data suggests that
staged decompression after every
dive will substantially reduce a
diver’s risk of DCI.
While we see an increase in risk
as dives get deeper, this effect is
not nearly as great as with longer
time. DCI can be expected to
occur occasionally, even in relatively
unprovocative exposures. Thus
it should not be regarded as an
accident because it does not always
represent a loss of control.
Studies suggest that stops need
to be made before significant bubbling
has occurred if a benefit is to
be realized. Spending, say, one
minute at 60 feet, 2-3 minutes at
3O feet and 5-1O minutes at 15
feet after each dive should
significantly reduce risk.
Can we trust recreational divers
to discipline their diving
to decrease DCI? Realistically I
think not, as studies show an
alarming number of divers who are
unable to manage even their air
supply. . . . However, I do hold out
hope for those who have a genuine
interest in reducing the risk of DCI
in their dive practice, mainly us
older, once bolder types.
The evidence is overwhelming
for staged decompression --
even following a dive profile that,
according to some algorithm,
incurs no decompression debt.
The objective after all is to reduce
the probability of DCI to an acceptable
minimum.