- "Sports Sci. 2009 Dec 3:1-16. [Epub ahead of print]
Decompression sickness in breath-hold divers: A review.
Lemaitre F, Fahlman A, Gardette B, Kohshi K.
Faculty of Sport Sciences, University of Rouen, Mont-Saint-Aignan,
France.
Although it has been generally assumed that the risk of decompression
sickness is virtually zero during a single breath-hold dive in humans,
repeated dives may result in a cumulative increase in the tissue and
blood nitrogen tension. Many species of marine mammals perform extensive
foraging bouts with deep and long dives interspersed by a short surface
interval, and some human divers regularly perform repeated dives to
30-40 m or a single dive to more than 200 m, all of which may result in
nitrogen concentrations that elicit symptoms of decompression sickness.
Neurological problems have been reported in humans after single or
repeated dives and recent necropsy reports in stranded marine mammals
were suggestive of decompression sickness-like symptoms. Modelling
attempts have suggested that marine mammals may live permanently with
elevated nitrogen concentrations and may be at risk when altering their
dive behaviour. In humans, non-pathogenic bubbles have been recorded and
symptoms of decompression sickness have been reported after repeated
dives to modest depths. The mechanisms implicated in these accidents
indicate that repeated breath-hold dives with short surface intervals
are factors that predispose to decompression sickness. During deep
diving, the effect of pulmonary shunts and/or lung collapse may play a
major role in reducing the incidence of decompression sickness in humans
and marine mammals."
- "Res Sports Med. 2006 Jul-Sep;14(3):163-78.
Decompression sickness following breath-hold diving.
Schipke JD, Gams E, Kallweit O.
Research Group Experimental Surgery, University Hospital Duesseldorf,
Germany.
schipke@med.uni-duesseldorf.de
Despite convincing evidence of a relationship between breath-hold diving
and decompression sickness (DCS), the causal connection is only slowly
being accepted. Only the more recent textbooks have acknowledged the
risks of repetitive breath-hold diving. We compare four groups of
breath-hold divers: (1) Japanese and Korean amas and other divers from
the Pacific area, (2) instructors at naval training facilities, (3)
spear fishers, and (4) free-dive athletes. While the number of amas is
likely decreasing, and Scandinavian Navy training facilities recorded
only a few accidents, the number of spear fishers suffering accidents is
on the rise, in particular during championships or using scooters.
Finally, national and international associations (e.g., International
Association of Free Drives [IAFD] or Association Internationale pour Le
Developpment De L'Apnee [AIDA]) promote free-diving championships
including deep diving categories such as constant weight, variable
weight, and no limit. A number of free-diving athletes, training for or
participating in competitions, are increasingly accident prone as the
world record is presently set at a depth of 171 m. This review presents
data found after searching Medline and ISI Web of Science and using
appropriate Internet search engines (e.g., Google). We report some 90
cases in which DCS occurred after repetitive breath-hold dives. Even
today, the risk of suffering from DCS after repetitive breath-hold
diving is often not acknowledged. We strongly suggest that breath-hold
divers and their advisors and physicians be made aware of the
possibility of DCS and of the appropriate therapeutic measures to be
taken when DCS is suspected. Because the risk of suffering from DCS
increases depending on depth, bottom time, rate of ascent, and duration
of surface intervals, some approaches to assess the risks are presented.
Regrettably, none of these approaches is widely accepted. We propose
therefore the development of easily manageable algorithms for the
prevention of those avoidable accidents."
A single dive won't give you DCS but who knows how many times he was diving at that time?