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The Bends


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#1 rohan

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Posted 25 May 2005 - 02:30 PM

G'day guys, anyone here know anything about the bends? I'm going to new zealand next week but I've been doing alot of spearfishing lately and am planning to do a bit on the weekend. How deep do ya have to go before it becomes an issue? I'm only snorkelling but I notice that sometimes I get a water logged ear. Is this a problem?
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#2 Jazman

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Posted 25 May 2005 - 04:05 PM

Hi Rohan
Are you going to be freediving or SCUBA diving? If you are freediving the bends is not a concern. How the bends happen is that if you stay at depth (and therefore at pressure) for long enough, nitrogen accumulates in the water in your body. If you come up from depth (and therefore into a lower pressure environment) too quickly, the nitrogen in the water in your body will come out as bubbles, which can lodge in your joints and cause 'the bends'. This will happen if you are SCUBA diving at depths of 30+ metres for extended periods (say 30 minutes or more), and ascend too quickly. If you ascend at an appropriate speed the nitrogen will come out without forming bubbles. If you are freediving you won't spend enough time at depth to accumulate enough nitrogen to cause the bends - this is why competition freedivers are able to dive to 160m+ depths, but the maximum depth for recreational SCUBA diving is around 50m. Also, since your are not actually breathing at depth while freediving, there is limited nitrogen available to accumulate in the water in your body, so again freediving is not a concern. I personally haven't freedived to much more than 10m, although some of the really good guys can get to 20 or even 30m, and stay there for a few minutes without getting the bends.

The biggest risk factor for freediving is shallow water blackout (SWB). SWB happens when you hyperventilate to increase your breath hold capacity, and pass out on the way back up. In short, DO NOT hyperventilate, although it does increase your breath hold the risks are just not worth it.

I'm not sure what could be causing your water logged ear, if you're worried about it go and see a doctor who specialises in diving medicine (there are a few around melbourne).

Jaz :beer
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#3 Chick3n

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Posted 25 May 2005 - 06:22 PM

Is the bends the same as a burst ear drum? If you are shallow water diving for depths at 3m will this be a problem?

Thanks,

Chick3n
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#4 Jazman

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Posted 25 May 2005 - 06:42 PM

Burst ear drums and the bends are totally unrelated.
The bends happens under the conditions I described above, burst ear drums happen when you fail to equalise the pressure in your ears while descending. Your ears have a small enclosed air gap inside them, at pressure the air in this gap expands, and if you don't equalise the pressure in the gap by 'popping' your ears you can rupture your ear drum. Your ears re-equalise the pressure (when you come up from depth) by themselves.
Popular ways of 'popping' your ears include holding your nose while trying to breath out through your nose, or doing a big yawn and manipulating your jaw until you feel the pop. Everyone should be familiar with pooping your ears, it happens sometimes if you drive up a big hill, or in a plane during take-off.
3m is about the maximum I would dive to without equalising, but it is a good policy to equalise in whatever depth of water you are diving in - your ears should let you know if they need equalising anyway ie/ if your ears start to become very painful, you need to equalise! If you feel pain on equalising, or cannot equalise at all, it may be because you have a cold or similar illness which swells the tubes in your ears, or may be something more serious - if in doubt see a doctor.
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#5 rohan

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Posted 25 May 2005 - 07:03 PM

Yeah thanks jazz man. I'm only free diving in water to probabely 5m, but it was just the fact that I was going on a plane soon after. I thought the bends had something to do with water in your ear drum under different pressures.
Sometimes if I spend a couple of hours out in the water constantly diving and equalising I end up with water trapped in my ears for a couple of days!

Hey jaz man you could be the forum online doctor: "Dear Dive Doctor, I have a rash on my balls..." :beer
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#6 Jazman

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Posted 25 May 2005 - 07:31 PM

lol Rohan, I'm happy to field questions about diving, as for the rash....show your mum and ask her what she reckons :beer :beer
As for diving and catching a plane, again it's only a concern if you've been SCUBA diving. During your dive training they recommend that if you're flying somewhere to go diving, that you don't schedule any dives on the day you fly. There have been cases of people getting in strife because they fly within a couple of hours of SCUBA diving....bad idea.
You learn all about the bends, pressure, equalising, decompression and heaps of other stuff if you do a SCUBA course - I'd highly recommend it to anyone who wants to add another dimension to their ocean experience. :ink
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