Feature: New diagnosis for the bends

By STEPHEN SHELDON  |  March 10, 2002 at 11:58 AM
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SYDNEY, March 7 (UPI) -- Medical researchers in Australia have developed a new test to help doctors cheaply, easily and accurately diagnose whether a scuba diver has decompression illness, commonly known as "the bends."

The bends affects more than 300 patients a year in Australia, more than 500 in the United States and thousands more worldwide. It generally occurs when a diver fails to follow correct diving procedures and absorbs excess nitrogen in their body.

The nitrogen bubbles cause a range of symptoms, including musculo-skeletal pain, tingling and nausea. The long-term effects can be quite severe, and include profound neurological damage, quadriplegia and even death.

The only cure is emergency treatment in a recompression chamber.

The trouble with the bends is because the symptoms often are subtle and non-specific, it can be difficult to diagnose except in extreme cases. As there is no simple test, doctors often are in a quandary about the state of a patient's health.

Unable to take the risk leaving the bends untreated, patients are rushed at great expense, and often unnecessarily, to a specialist hospital with a recompression chamber. Recompression chambers are scarce. Only eight Australian hospitals have one.

Hyperbaric physician, Dr Michael Bennett, from the University of New South Wales in Sydney, devised the new test. It involves counting the number of tiny air bubbles in the tear film in the lower eyelid using an optometrist's tool called a slit lamp.

In his study, Bennett measured bubbles in the tear film of healthy divers, as well as in divers who had the bends.

He found when a person scuba dives safely, they have two or three air bubbles in their tear film. But a diver with the bends has between 10 and 30 bubbles. The bubbles are present for about two days after the dive, and then go away.

"We can now conclude for the first time that if a diver has more than 10 bubbles, then it is more than likely they have the bends and should be sent to a hyperbaric chamber," Bennett told United Press International.

His findings are supported by Dr. Simon Mitchell, a physician at Queensland's Wesley Centre of Hyperbaric Medicine.

"This study has discovered for the first time the existence of elevated tear-film bubble counts following compressed air breathing by divers," Mitchell told UPI.

The physicians said it is a major advance in hyperbaric medicine and likely will replace current tests using an ultrasonic Doppler monitoring, which measures bubbles in a patient's bloodstream.

"The trouble is that bubbles in the blood do not necessarily mean you have the bends," Dr. David Doolette, from the University of Adelaide, told UPI. Doolette also said counting tear film bubbles using a slit lamp is easier and more reliable than the Doppler method.

"Our research may result in a test for the bends that can be done by any doctor, anywhere," Bennett said. "We hope that a remote area doctor, suspicious that a patient may have the bends, will be able to do a simple, inexpensive examination of the patient's tear film. Based on the number of air bubbles they will then be able to make a decision on whether the patient needs to be flown out for further treatment."

Bennett said, however, a bubble count would be a confirmatory rather than a primary diagnostic tool. "Bubble counts would never over-ride the patient's other symptoms," he says.

For divers who think they may have the bends but actually do not, the bubble count test may relieve their stress on the spot and let them continue their diving trip.

The test will be of particular interest to Australia, which has the busiest hyperbaric hospital in the world -- at Townsville near the Great Barrier Reef.

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