Yes its Mauro's fault. Now its twice I've had to get up early in the
morning to fit in some chat before the days work. Addictive isn't it?
RE- my earlier comments on decompression sickness. Andrew Taylor has
pointed out to me that there are cases of human decompression sickness from
free diving!! I was stunned. None of my texts on deep diving or
sub-aquadic medicine mention this. Following this revelation I phoned HMAS
Stirling here in Perth and discovered the following. Based on their
experience no recreational or pearl diver has been bent from free diving,
however in the past they have had a few incidences of Navy personnel getting
DCS from frequent breath hold dives into their 20m diving tank. On these
dives they held their breath for 3 minutes (a little beyond me I'm afraid).
The likely cause of the DCS was a number of consecutive free dives with a
rapid ascent. They now limit the number of dives to 10 a day and have had
no further problems. One thing that came out of the conversation was that
these divers take as large a breath as possible and keep that air in their
lungs until they return to the surface. Many recreational free divers
however, dribble off air when they are under the water (this should be safe
as long as you do not hyperventilate on the surface before you dive and you
are not tearing around down there exhausting your oxygen supply). Reflecting
back on our earlier chat it made me wonder whether keeping a huge lung full
of air enhanced DCS?? Thanks for the info Andrew, but I am still stunned
that one breath of air could bring on DCS.
This made me wonder about my statements on Nitrogen Narcosis and Oxygen
Toxicity. I consulted my old animal physiology book which stated "Diving
animals are not subject to the dangers of oxygen toxicity or the narcotic
effects of inert gases for the simple reason that they do not breath a
continuous supply of air during the dive". This statement supports my
thoughts outlined in my previous e-mail, but the book is quite old. Is this
still the case or has there since been evidence to the contrary??
Cheers Julie.
P.S. In reply to Pat's question, "What do you divers see down there?", we
see penguins with the latest in internal scuba tank technology of course.
Julie Raines
Australasian Ecological Services
E-mail
Snail PO Box 312, Wanneroo, Western Australia 6065
Tel/fax + 61 9 306 1642 Mobile 014 081 702
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