Last Updated: 11 December 2018
An air or gas embolism is
a bubble that becomes trapped in a blood vessel and blocks it. This can lead to
many different symptoms depending on where the blockage occurs. It's one of the
leading causes of death among divers. An air or gas embolism can happen when a scuba
diver surfaces too quickly from any depth. This can cause air to escape into
the blood vessels from the lungs (pulmonary barotrauma) or bubbles of nitrogen
to form in the blood vessels (decompression illness, or "the bends").
An embolism can develop in an artery or vein. When
an air bubble travels along an artery, it moves through a system of blood
vessels that gradually become narrower. At some point, the bubble may block a
small artery and cut off the blood supply to a particular area of the body. Bubbles in the veins travel around the body and can
cause breathing difficulties when they reach the lungs.
How
serious is it?
The seriousness of the blockage depends on which
part of the body the affected blood vessel supplies blood to and the size of
the air bubble. For example, an air embolism in:
- the
arteries to the brain can cause immediate loss of consciousness and may
lead to seizures (fits) or a stroke – it can also cause
confusion, dizziness and slurred speech
- the
coronary arteries (which lead to the heart) may cause a heart attack or an abnormal heart
rhythm
- a
blood vessel to the lungs may cause a pulmonary embolism.
These conditions are very serious and can be fatal,
particularly if an air embolism is not recognised and treated promptly. Even with treatment, some people who survive are
left with permanent brain damage, although this is very rare.
Warning signs
Divers should always be carefully monitored by
their colleagues and supervisors so any air or gas embolism can be immediately
identified and treated. Signs and symptoms of an air embolism can include:
- joint
or muscle pains
- low blood pressure, which may cause dizziness
- an
irregular heartbeat
- breathlessness and fast breathing
- blurred
vision
- chest pain
- strong
feelings of anxiety and itching of the skin
- a
faint blue tone to the skin (cyanosis)
- bloody
froth from the mouth
- paralysis or weakness, possibly
of one or more limbs
- seizures
(fits)
- loss
of consciousness.
If a scuba diver develops these symptoms within 10
to 20 minutes of surfacing, they probably have an air embolism and should be
given 100% oxygen and transferred to hospital as soon as possible, preferably
one with a recompression chamber.
Treating
air embolisms
If a diver develops an air embolism, the only
effective treatment is immediate recompression treatment in a special
pressurised room called a hyperbaric chamber. The diver should be given 100% oxygen and laid horizontally
until they reach the hyperbaric chamber.
Recompression treatment involves lying in a
hyperbaric chamber, usually for several hours, and breathing a mixture of gases
and oxygen under pressure. The high pressure can restore normal blood flow and
oxygen to the body's tissues and reduce the size of the air bubbles in the
body.
In cases of decompression sickness, the pressure
forces the bubbles of nitrogen to dissolve back into the bloodstream. After recompression, pressure is reduced gradually
to allow the gases to leave the body without worsening the problem, similar to
surfacing slowly from a dive. Treatment might be continued for several days
depending on the severity of symptoms.
Preventing
an air embolism while diving
The following advice can help reduce your risk of
developing an air or gas embolism when diving:
- Limit
the depth and duration of your dives.
- Come
up to the surface slowly and always perform safety stops to allow any air
in your tissues and blood vessels to escape safely. Use a dive computer or
dive tables, and don't dive again if you have broken these rules until you
have had a suitable time at the surface.
- Don't
dive with a cold, cough or chest infection.
- Avoid
rigorous exercise before, during and after a dive.
- Make
sure you're well hydrated before diving.
- If
planning several dives, leave adequate surface intervals between dives to
allow the nitrogen to leave your body.
- After
diving, wait for 24 hours before flying or going to a higher altitude.
If in doubt, contact a dive professional or doctor,
who can provide further advice.
Other
causes of air embolisms
Air embolisms also occur during surgery or
other medical procedures, but this is rare. In hospitals and health centres, care should be
taken to prevent this. For example:
- before
injections, air should be removed from syringes and intravenous lines
- catheters
or other tubes inserted into the body should be inserted and removed using
a technique that minimises the possibility of air getting into the blood
vessels
- patients
should be closely monitored to help ensure air bubbles don't form in blood
vessels during surgery.
Air embolisms resulting from surgery, anaesthesia
or other medical procedures can be difficult to treat. Treatment is usually
needed to support the heart, blood vessels and lungs.
For example, fluids may be used to treat a fall in
blood pressure and oxygen may be given to reduce levels of other gases in the
blood vessels.
Source: NHS Choices