Simply breathing compressed
air at depth presents another potential for mishap. As well trained and
experienced as we will certainly become during our sport diving career,
the potential for Decompression Illness will always exist. Many years
of scientifically catalogued and collected data demonstrates that even
when exactly following the various safe, conservative and
internationally approved recreational dive profile tables, divers may
still experience incidents of pressure related injury. Not all human
bodies fit exactly to the normal standards used in the algorithmic
derivation of these generally quite safe dive profiling systems.
We can divide into two sub-groups, this potential for pressure injury.
The first of these 2 sub-groups, Decompression Sickness (DCS), can
manifest as either Decompression Sickness
- Type I ...pain only, usually
in the joints or muscles, or the potentially more serious Decompression
Sickness
- Type II...a typical diagnosis of Type II DCS indicates that
symptomatic evidence of Central Nervous System involvement is present.
Decompression Sickness onset can be directly related to our return to
the much lower pressure found at the surface after completion of our
dive to the higher pressures encountered at depth. DCS is caused by the
relatively uncontrolled release of Nitrogen gas from it's temporary
state of complete liquid solution within the blood and various body
tissues. Nitrogen Gas dissolves into solution painlessly, and this
occurs after prolonged breathing of compressed air under the pressures
encountered during our immersion. During our dive, remember that we
breathe a higher than usual concentration of Nitrogen gas, under
pressure, from our SCUBA cylinder at depth. The result is pretty
predictable... the longer we breathe the compressed air at depth, the
more time this "larger than normal" quantity of Nitrogen gas has to
dissolve into our blood and our variety of body tissues. While we are
under pressure, this dissolved Nitrogen gas will stay in solution.
Think in terms of a pressurized, carbonated soft drink suddenly opened
to a state of lower pressure. The carbonated gas which was safely
contained in a state of solution while pressurized, now fizzes (or
bubbles), transformed from a state of complete liquid solution back to
a gaseous state as the surrounding pressure lessens upon removal of the
soft drink bottlecap.
Similar conditions give rise to the potentially unregulated release of
Nitrogen from solution in our body's blood and tissues as a return to
the lower pressure at the surface allows it's transformation once
again, into a gaseous state.
This free Nitrogen gas begins as micro-bubbles, these bubbles can
merge, growing larger as the pressure surrounding the diver's body
continues to lessen and as the tissues and blood surrender their gas
load under the condition of decreased pressure as we return towards the
surface. These expanding gas bubbles have the potential to collect,
causing clotting and may obstruct nerve signal transmission, leading to
the loss of feeling (DCS Type II), or again, potentially, to collect at
joint sites or in muscle areas causing a steadily progressive sensation
of pain or soreness (DCS Type I).
Symptoms of DCS can manifest as long as 48 hours following a dive,
although the historical data collected demonstrates that nearly 75% of
DCS symptoms develop within 4 hours, post-dive. Many afflicted divers
will exhibit DCS symptoms within 12-24 hours following their immersion,
athough as presented above, some divers may not develop symptoms for as
long as 48 hours post dive. Following precisely our dive profiles, and
observing strict discipline about the importance of regulated surface
intervals is a pretty dependable way to avoid DCS. But it DOES happen,
even when we observe all the guidelines. No one can explain this,
except by pointing out that the perfect dive time and depth profile
table has not yet been formulated that would protect ALL divers under
ALL conditions. Dive smart--dive safe....and be prepared.
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