Dive computers and 'Bends'

[budgy]

I just don't seem to do dives that need a computor to work out deco stops.

[Mark Chase]

I dont understand

I know a lot of old bauld divers :0

Mark Chase
Dyslexic Diver

[Dr Stevil]

Careful Mark,  you'll be banned from the Dyslexics club for spelling it correctly ;)

[John Gulliver]

For spelling what correctly? Not bald, anyhow! But maybe Mark meant old bawdy divers. I know a few of those.

[Dr Stevil]

"I used to be dyslexic but now I'm only partially dyslexic, someone said no you're not as dyslexic as me, so you're only partially dyslexic,  there's a lot of rivalry in the dyslexia camp, rivalry with three 'v's..."

Eddie Izzard "Glorious"

[Seadart Bob]

i fink i am missing somfing ere wots dislexia got to do wiv dive computers??

[angus Theape]

One of the things you have to consider is that a "bend" is viewed as a venous thing, excess N2 not being released properly from the tissues. Thus joint pains, paralysis etc. in simple terms caused by from inadequate decompression to bad luck from a normal ascent.

Peter, what you suffered from has all the symtoms of a CNS problem and therefore viewed as arterial. There are basically two ways of getting this problem. Rapid ascent was little or no decompression. In this situation, the N2 micro bubbles are in such excess they have not the time to dissapate from the lungs and pass to the arterial side, this you did not do. Or a PFO, where the micro bubbles from a normal ascent bypass the lungs and pass directly to the arterial side of the heart.

The distinction between venous and arterial problems are academic as far as treatment is concerned, the treatment being the same. The difference being how the problem arose to cause the incident.

In your case, I suspect you have a PFO that is normally closed, but is not actually sealed. When you moved the barrel, the exertion opened the pfo allowing the micro bubbles to shunt across your heart thus bypassing the lungs.

The mere fact that the "pooter" is on your wrist as against being on your desk, makes no difference to what it adds. All the computer is doing is measuring the amount of N2 the algorythm calculates you have absorbed. The desk top can basically only calculate a rectangular profile dive unless you have a special dive profile you intend to follow exactly. The wrist model simply calculates from the same algorythm, but on what you are actually doing on the dive.

Remember computers are stupid, they only do exactly what a human being told them and can only count to 1.

(Edited by angus Theape at 2:39 am on Feb. 16, 2003)

[peter k]

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Originally Posted by [b

Quote[/b] ]Quote: from angus Theape on 2:36 am on Feb. 16, 2003
In your case, I suspect you have a PFO that is normally closed, but is not actually sealed. When you moved the barrel, the exertion opened the pfo allowing the micro bubbles to shunt across your heart thus bypassing the lungs.

<span =''>

Hi Angus,
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;What does moved the barrel mean and would exertion have caused this barrel to move? If what you are saying is correct, Why does the PFO go from a closed state to an open state? Again, would exertion cause this as both my bends have been preceded by exertion and the last one was finished with exertion? You make a bit of sense so far.

Peter &nbsp;

[Ian W]

</span>

Originally Posted by [b

Quote[/b] ]Quote from Peter K at 2:22 pm on Feb. 16, 2003
What does moved the barrel mean and would exertion have caused this barrel to move? If what you are saying is correct, Why does the PFO go from a closed state to an open state?

<span =''>
Peter, you said in your original message describing your incident that after the first dive you had a long walk back up a steep hill in full kit and then helped someone push a barrel over. That kind of effort can cause differences in blood pressure between the right and left sides of the heart that can open a PFO and allow bubbly blood to be squeezed through to the arterial circulation. The tests for PFO involve injecting bubbles into the venous bloodstream and getting the subject to cough or do a strong valsalva manouevre or something similar to generate a pressure difference in the heart, then they use ultrasound to look for bubbles in the arterial side.

However, Angus seems to have confused neurological decompression sickness with arterial gas embolism. Neurological DCS could occur without arterial bubbles. The fact you had neurological symptoms (weakness, numbness, visual disturbances) does not prove you have a PFO, although your case history suggests you might well have. On the other hand, your computer let you do two deep dives with a fairly short surface interval, which is known to be provocative.

Ian W

[peter k]

Oh, THAT barrel. I thought it was either a euphamism for something or medical speak for a bit of my heart.

Thanks
Peter