Basic HTML Version
Chapter 13 — 6
!
Individuals.
Some people are to be more susceptible to DCS than others. Even an individual may vary in
susceptibility at different times, and DCS can develop after a dive profile which has been
safely followed on many previous occasions. Others frequently get DCS despite conservative
diving.
!
Adaptation.
Repeated dives to similar depths over a period of time reduce the incidence of DCS. This may
be due to the elimination of bubble nuclei. A diver returning to these dives after a 2 week
break loses the benefits of this adaptation or acclimatisation.
!
Age.
Older divers
tend to be more predisposed to DCS (an old diver can be defined as anyone
older than the senior author of this text). This age factor probably comes into play after the 3
rd
decade.
!
Obesity.
This appears to be a predisposing factor probably due to increased N
2
solubility (4-5 : 1) in
fat compared to water (obesity is defined as anyone heavier than the biggest author). This
may be relevant for those with a BMI of > 25.
!
Debilitation.
Factors causing the diver to be unwell such as
dehydration, hangover
or
exhaustion
tend to
predispose to DCS. Fatigue (pre-dive) is observed in some cases.
!
Injury.
DCS, particularly involving the musculo-skeletal system and joints, is more likely with recent
bruises, strains or chronic injuries.
!
DCS.
A previous episode of DCS, especially if it was unexpected from the dive profile, or if it
damaged tissue (as in neurological DCS), makes the diver predisposed to similar subsequent
episodes.
!
Patent Foramen Ovale.
One reason for some people to have an increased susceptibility to DCS is that they have a
small hole in their heart. All of us had a hole in our heart when we were a foetus. In about a
third of the population some remnant of this hole remains, it is called a patent foramen ovale,
or PFO. These people have an increased susceptibility to DCS, the likely reason is that
bubbles that would normally be trapped in the lungs without causing symptoms pass through
the hole, by-passing the lung filter, and on to other parts of the body, where they cause
noticeable symptoms. However, the risk from a PFO is not great enough for it to be
appropriate to test all divers for it, and repair of the hole is probably more dangerous than
diving with it.