Trouble with bubbles in your body

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Posted by on February 13, 2005 at 19:03:04:

UNDER PRESSURE: Diver Hans Renner recovered after suffering the bends when he surfaced too quickly.

As Hans Renner struggled to suck a last gasp of air from an empty tank, he knew he was in trouble. Deep trouble.

Lured to an interesting-looking rock and distracted from his air gauge by the far more engaging spectacle of the wall-to-wall crayfish living around it, he suddenly found himself running on empty in deep water.

"The first sign you have that you've run out of air is it actually stops. You take a breath and it's okay and the next breath you are thinking `shit'."

At the time about seven years ago Mr Renner, now 45, was diving in one of his favourite spots out the back of Taputeranga island in Island Bay, at about 40 to 43 metres.

"It was almost an emergency ascent. I finned to the surface but did not have to drop my weight belt or catch bag. I remember as I was coming up thinking, `I'm in the shit here. This is definitely not in the textbook.' But I did not have any choice."

Surfacing from that depth, Mr Renner should have ascended slowly, making a recompression stop in shallow water to allow his system to get rid of any nitrogen dissolved in the body tissues. Coming up quickly with no stop he was at serious risk of succumbing to a diver's biggest fear or perhaps a close second to sharks the bends.

"When I got to the surface I had a splitting headache. It was like someone had hit me on the back of the head with an axe."

Back on shore Mr Renner noticed he had a sore bottom, leg and hip, but thought nothing of it. Thinking he had come out okay, he took a couple of aspirin and went to bed.

That was Wednesday, the beginning of a run of amazing weather. When the next day dawned sunny and calm, the temptation to get back in the water was just too great.

"We did back-to-back dives to about 24 metres. When we got back to Island Bay my leg was so stiff I had trouble getting off the boat after washing it down.""

Unfazed, Mr Renner took another couple of aspirin and set off to his regular cards and darts night. "I was that sore that I could barely sit down and could not stand in a controlled way to play darts. I was home by eight o'clock, instead of the usual midnight."

But he still thought nothing of it, and when he woke on the Friday to another stunning day he could hardly refuse his dive instructor buddy's suggestion of another dive.

"I can remember trying to get off the boat and on to the road. I just about could not do it. I could not move my left leg. My mate said, `What the hell's wrong with you?' "

When he explained the week's activity, his dive instructor friend immediately worked out he had the bends and ushered him off to hospital, where he was in so much pain it took him 10 minutes to get out of the car and across the road.

The doctor quickly confirmed the diagnosis and Mr Renner was rushed to Devonport Naval Base by air ambulance.

"It was just incredible. It felt like somebody had got a rusty six-inch nail and hammered it into my hip and was trying to drag it back out with a crowbar."

Mr Renner spent his Friday night sucking on oxygen in the recompression chamber, feeling a little sheepish under the watchful eye of the chamber nurse. The chamber reduces the nitrogen bubbles by increasing the pressure and allowing the body to slowly get rid of the excess gas.

Being put on to the ward the next day was sobering and made him realise how lucky he had been.

"There was a guy in the bed across from me who was paralysed he had been diving for food for his father's tangi. I was set to cry he could not get out of bed into his wheelchair.

"The guy next to him could not move his shoulder he was a builder."

Over the next four days he was in and out of the chamber, spending progressively shorter periods each time and gradually reducing the simulated depth.

On the ward, every sip of water entering and leaving his body had to be meticulously measured to check his bladder was working properly.

In the chamber the searing pain went away, but he was still hobbling around. Even now he walks with a limp.

"My left leg has been permanently damaged. I still limp and in a cold southerly it hurts like hell."

He still lives for diving, but the terrifying experience has made him much more conservative underwater.

"When I got home (my wife) Ingrid said, `Before you go diving again you are going to get a dive computer.' It does not make you a better diver but it helps calculate multiple dive profiles."

He admits his bout of the bends was "dumb" but he learned to dive at the age of 13, when dive tickets were unheard of. His father taught himself to dive, after being given a set of scuba gear when the family was living by the Red Sea.

Mr Renner dived on instinct and without incident for more than 15 years before getting certified.

Devonport Naval Hospital hyperbaric medical officer Chris Sames says the number of people he treats every year for the bends has dropped from about 80 to 90 five years ago to 30 to 35 now possibly because of better diver education.

THE BENDS was first recognised in coal miners working in pressurised tunnels in the mid-1800s. They suffered muscular pains and walked holding their lower back, resembling the fashionable women of the time who walked with hands on hips in a posture known as the Grecian Bends. Hence the term the bends.

When divers are underwater they breathe compressed air, made up of about 80 per cent nitrogen a space-filler not used by the body. At depth it dissolves into the body tissue, Dr Sames says.

As a diver surfaces and pressure drops, the gas expands and forms bubbles, which usually travel to the lungs and are breathed off. But if the bubbles expand too quickly and the gas comes out of the tissues into the blood, they can go into the brain or block blood vessels and limit blood supply.

"It's like taking the top off a coke bottle. Coke has dissolved carbon dioxide you don't see that till you rapidly take the top off and release the pressure. It's the same with divers.

"The danger, really, is in how long they stay under, how deep they go and how quickly they come up."

Divers with the most serious form of the bends where bubbles go into the brain can have symptoms as soon as they surface, including loss of consciousness, which can lead to drowning. They can also experience convulsions and personality changes. If bubbles get into the spine, they can cause paralysis.

More minor symptoms include headaches, lethargy, joint aches and a general feeling of unwellness, Dr Sames says.

These may go away naturally, but it is safer to treat them because the condition may worsen.

The sooner a diver goes into recompression the better. Patients are usually flown by helicopter or air ambulance to the navy hospital, or a unit in Christchurch, to be assessed.

People with minor symptoms usually spend about 1-1/4 hours in the recompression chamber, which is pressurised down to a depth of about 18 metres. This squeezes the nitrogen bubbles so they dissolve.

"The `coke' is repressurised and the bubbles disappear. In the slow ascent phase they breathe off the nitrogen safely," Dr Sames says.

Divers often recover with just one treatment, but more serious cases, such as Mr Renner's, require repeat recompression. Even after the nitrogen has been removed, there can be permanent damage. The bubbles can damage nerves or the fragile lining in blood vessels, causing clotting or swelling, which is just as dangerous as the bends itself.

Recompression treatment is not cheap, ranging from $3000 to $10,000, depending on severity and not including travel by helicopter or air ambulance. ACC picks up the tab.

Other than the obvious, fitness is the biggest single factor influencing whether divers get the bends, and people should have regular medical check-ups to make sure they are fit to dive, Dr Sames says.

Most of those treated are responsible divers who have had an accident or gear problem, but some just run out of air through carelessness.

Dive tables and dive computers give a good indication of how to dive safely without getting the bends. But they are not infallible. On one recent dive, Mr Renner's dive computer showed he had 18 minutes of safe bottom time left when he surfaced, but his buddy, who had done an identical dive, got the bends.

Though cases of the bends can be serious and the treatment numbers do not include those who die before they make it to recompression, the incidence is very low considering tens of thousands of divers do hundreds of thousands of dives in New Zealand every year, Dr Sames says.

"Generally it is not that dangerous. By and large, everyone comes home safely.

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