the past 20 years sport diving has become extremely popular,
both at home and abroad.
However, diving is not without its dangers and it is
vitally important that divers become suitably qualified to
undertake any proposed dives.
Qualifications can be obtained by joining a club and
undergoing a training course or by attending a recognised
diving school for training, and subsequently making sure that
you keep your skills up to date.
must be planned and carried out in a responsible manner,
making sure that first aid equipment and relevant telephone
numbers are at hand should an accident take place.
Finally, it is important to know the signs of decompression
sickness and to be able to give first aid to an affected diver.
sickness, also called the bends, is caused by nitrogen bubbles
forming in the bloodstream and tissues of the body. The bubbles
occur if you move from deep water towards the surface (where
the surrounding pressure is lower) in too short a space of
occur soon after the dive has finished and, in the most serious
cases, it can lead to unconsciousness or death.
suspect decompression sickness, stop the dive, initiate first
aid, and summon assistance from a specialist in divers' medicine.
Treatment is 100 per cent oxygen on site and during transportation,
followed by treatment in a decompression chamber.
if you or your buddy
the diver becomes unconscious, give first aid.
the emergency services immediately.
pure (100%) oxygen if available.
over-exertion. Lie the victim down with their feet
plenty of liquid.
unusual condition after a dive should be considered
as decompression sickness until proven otherwise.
So always get medical help.
are the symptoms?
of decompression sickness vary because the nitrogen bubbles
can form in different parts of the body.
may complain of headache or vertigo, unusual tiredness or
fatigue. He or she may have a rash, pain in one or more joints,
tingling in the arms or legs, muscular weakness or paralysis.
Less often, breathing difficulties, shock, unconsciousness
or death may be seen.
generally appear in a relatively short period after completing
the dive. Almost 50 per cent of divers develop symptoms within
the first hour after the dive, 90 per cent within six hours
and 98 per cent within the first 24 hours.
this means symptoms that appear more than 24 hours after the
dive are probably not decompression sickness.
An exception is if the diver has travelled in an aircraft
or has been travelling in the mountains. Under these circumstances,
low pressure can still trigger decompression sickness more
than 24 hours after the last dive. As a result, it is wise
not to fly within 24 hours of a deep dive.
Why does it happen?
Nitrogen makes up 79 per cent of the air we breathe (in
the air around us and in our diving bottles). During a dive,
large amounts of nitrogen are taken into the body's tissues.
This is because the diver is breathing air at a higher pressure
than if they were at the surface.
of dissolved nitrogen depend on the depth and duration of
the dive. The deeper and longer the dive, the more nitrogen
is taken up by the body. This does not present a problem as
long as the diver remains under pressure.
the diver begins to ascend to the surface, the surrounding
pressure falls, and nitrogen is released from the body via
the lungs when the diver breathes out.
If the rate of ascent exceeds that at which nitrogen can be
released, it forms bubbles in the blood and tissues (similar
to opening a bottle of fizzy drink too quickly).
minimise the risk of bubbles forming and divers developing
decompression sickness, various tables have been drawn up
that show the relationship between a given depth of water
and the time a diver can stay down.
divers are advised to make a safety stop every 5m, and not
to ascend at a pace of more than 10m a minute. If the dive
has been deep or of long duration, it may be necessary to
stop one or more times on the way up, making so-called decompression
following the advice of the tables is no guarantee of avoiding
decompression sickness. This is because the risk of developing
decompression sickness is not only determined by the depth
and length of the dive, but also by any safety/decompression
stops. Factors such as cold, current, exertion and lack of
fluid also play a part.
characteristics such as age, sex, percentage of body fat and
physical condition must also be considered. Women are more
at risk of decompression sickness than men. Similarly, the
risk becomes greater the older the diver and also depends
on the level of physical fitness.
is it diagnosed?
most cases, the diving history (ie information on the number
of dives, diving depth, dive time, rate of ascent and decompressions)
as well as information on contributory factors such as cold,
current, work and the diver's physical condition will give
some indication as to whether it could be decompression sickness.
a thorough examination, which includes investigating balance,
coordination, sense of touch, reflexes and muscular strength,
the doctor can build up a complete picture to evaluate whether
decompression sickness is likely.
will also decide if the diver requires treatment in a decompression
chamber (also called a hyperbaric or recompression chamber).
measures can be taken to avoid decompression sickness?
within the limits set out in the diving tables.
your rate of ascent to a maximum 10m/min.
plan any dives that need a decompression stop in the water.
a 3 minute safety stop at a depth of 5m, (or 1 minute at
dive more than three times in one day.
you plan more than one dive in one day, start by making
the deepest dive first.
you are diving for several days in a row, have a dive-free
day after two to three days.
do any hard work before or after diving.
lots of liquid before diving. Lack of fluid due to heat
or excess alcohol is dangerous.
sure you are in good physical condition and well rested.
Have regular medical checkups.
sure there is an interval of at least 24 hours between diving
and travel by air or climbing up mountains. If you have
had decompression treatment, the recommended interval before
the next dive is at least 48 hours.
after decompression sickness
forms of decompression sickness can resolve themselves without
treatment or by breathing 100 per cent oxygen at the site
of the accident.
if there is any suspicion of decompression sickness, the diver
must be examined by a doctor. This is because although it
might not seem serious at the time, the condition may deteriorate.
the diver receives treatment at an early stage, the chances
of avoiding permanent injury are good. The longer that treatment
is delayed, the greater the risk of serious consequences.
should take a rest from diving after treatment for decompression
sickness. The length of this rest depends on the severity
of the decompression sickness and the effects of treatment,
and should be discussed with a specialist in divers' medicine.
is decompression sickness treated?
is no medicine that is used as a matter of routine in treating
the dive site and during transport
100 % oxygen.
diver plenty of fluids if conscious.
first aid if appropriate.
the casualty from exerting himself or getting cold.
hospital and specialised centres
decompression chamber is a steel tank that can be pressurised.
are decompression chambers in various places in the UK - some
of these are situated at naval centres.
The pressure in a decompression chamber is increased by closing
the doors and pumping air in.
During treatment for decompression sickness, pressure is increased
to correspond to the pressure found 18m under water. In some
cases, the pressure in the chamber is set at 50m.
casualty breathes pure oxygen through a mask, which improves
exhalation of nitrogen.
At depths in excess of 18m, and also after adequate intervals,
the mask can be removed in the chamber. Pressure in the chamber
is reduced gradually until the diver reaches surface pressure
typically lasts between five and six hours.
treatment a specially trained helper stays with the diver
in the chamber. The diver's condition is closely monitored
by further examination of coordination and balance, sense
of touch, etc.
necessary, the diver's medical specialist can join the diver
in the chamber, but otherwise takes charge of the treatment
outside the chamber in co-operation with the specially trained
treatment, the diver will be kept for 24 hours for observation
in case his condition deteriorates.
most instances one course of treatment is adequate, but occasionally
several treatments may be needed.
treatment for decompression sickness, a diver should take
a rest from diving. The length of this rest should be discussed
with a specialist in divers' medicine.