APART from a shark attack, the “bends” are a scuba diver’s worst nightmare.
But an underwater wristwatch developed in Scotland could soon give divers ample
warning that they are heading for serious trouble.
The device monitors the amount of air dissolved in divers’ blood, and warns
them to ascend more slowly if it is approaching danger level.
The longer divers stay underwater, the more dissolved gas accumulates in
their bodies. When surfacing, divers have to allow time for this gas to be
expelled as the pressure of the surrounding water falls. The bends, also known
as decompression sickness, occur when a diver comes up too fast from a dive and
the gas forms dangerous bubbles within the body. Symptoms vary from harmless
skin rashes to paralysis, or even death.
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Divers normally rely upon their own calculations and timekeeping to keep the
gas levels in their blood within safe limits. If things go wrong, the only way
to determine whether someone has the bends is to use an ultrasound system on the
surface, says Ken Forbes of Heriot-Watt University’s International Centre for
Island Technology in the Orkney Islands. A technician gauges the extent of
decompression by comparing the way ultrasound is reflected by the diver’s blood
with pre-recorded samples.
Forbes now aims to remove any room for error by giving divers real-time
information while they are underwater that prevents the bends altogether. “We
want to totally automate the system,” says Forbes.
Helped by funding from Britain’s Health and Safety Executive, Forbes is
developing a wristwatch-like device that beams sound waves into the wearer’s
wrist. Software in the gadget analyses the reflected signals to calculate the
amount of gas in the blood to give the diver a read-out of the key figures.
Forbes is using a bubble generator to test the accuracy of his invention.
“Not too many people die from decompression sickness,” says Forbes. “But
those that get it require a lot of medical support.” He envisages fitting each
device with a smart card that keeps a record of all the wearer’s activity. “It
will constantly monitor the diver during, before and after the dive.” John
Harrison of the British Hyperbaric Association in the Wirral says there are
around 400 cases of decompression sickness each year in Britain alone.
Although the wristwatch will primarily be used by commercial divers, who are
most at risk, Forbes says it could also benefit recreational divers. At Scapa
Flow in the Orkney Islands people do a lot of recreational diving over a short
period of time. “Sometimes it’s two dives a day for six days back-to-back,” says
Forbes. “It’s one of the worst types of diving you can do. But they are all on
holiday and think they are invincible.”
“If this device can train you to modify your dive it could be a big help,”
says Harrison. “If you can minimise the bubbles you’re going to reduce the
amount of decompression sickness.”