down current, upwell at safety stop

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xrcjdx

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about a month in a half ago i had an exciting dive at verde island. after being pushed down to about 42 meters during descent before bringing that under control, the dive continued normally until the safety stop, by this time blown well off the reef into the blue. after a short time at 5 m was blown down to about 10 m (guess) before regaining the 5 m mark. shortly thereafter was pushed up nearly to the surface. descended again to 5 m and because the computer was treating this as a blown safety stop there was no further countdown. manually timed a 5+ minute stop at a relatively level 5 m before surfacing. post dive was normal, with no ill effects. same for buddy, who had nearly the same profile but maintained control at the safety stop somewhat better than i did.

question: once the safety stop is blown as this one was, does it do a body any good to descend to safety depth and resume/restart a stop? my instinct is once the cap is off the bottle any benefit from regaining depth is marginal at best, but i don't recall seeing this issue discussed before, even though i assume it is a relatively common experience. please forgive me if i didn't search hard enough for an answer before posting.

r
 
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Dr Deco

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--------- Post added October 5th, 2015 at 09:50 AM ----------

I believe that redoing the stop is of some value. It will assist in the shrinkage of bubbles [to a small degree].
 

Pearlman

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about a month in a half ago i had an exciting dive at verde island. after being pushed down to about 42 meters during descent before bringing that under control, the dive continued normally until the safety stop, by this time blown well off the reef into the blue. after a short time at 5 m was blown down to about 10 m (guess) before regaining the 5 m mark. shortly thereafter was pushed up nearly to the surface. descended again to 5 m and because the computer was treating this as a blown safety stop there was no further countdown. manually timed a 5+ minute stop at a relatively level 5 m before surfacing. post dive was normal, with no ill effects. same for buddy, who had nearly the same profile but maintained control at the safety stop somewhat better than i did.

question: once the safety stop is blown as this one was, does it do a body any good to descend to safety depth and resume/restart a stop? my instinct is once the cap is off the bottle any benefit from regaining depth is marginal at best, but i don't recall seeing this issue discussed before, even though i assume it is a relatively common experience. please forgive me if i didn't search hard enough for an answer before posting.

r

Isnt that what is attempted in a decompression chamber? Go back to "depth" and ease off?

I dived Verde in May - what dive site was this? Washing machine?

P
 

phoenix31tt

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Remember safety stops are optional and precautionary... if you are at the surface and not in deco i would not go back down in those conditions to finish off any safety stop. You take a greater risk by going down in those conditions than by skipping the stop.

if you computer locks you out because of a blown safety stop... get a new computer :D

---------- Post added October 5th, 2015 at 03:47 PM ----------

Isnt that what is attempted in a decompression chamber? Go back to "depth" and ease off?

But a recompression chamber is controlled and you are doing it with oxygen and an attendant. From all the books i've read about diving, it is never recommended to attempt in water recompression.
 

Akimbo

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… From all the books i've read about diving, it is never recommended to attempt in water recompression.

It is a repetitive or dive continuation if you are symptom free, not a DCS treatment — in the water or in a chamber. Returning to the max depth does not make sense in most cases and is not how you would be treated in an omitted decompression incident if you had a chamber onboard.

The VAST majority of DCS chamber treatments run to 60' max, while actual symptoms often resolve above 40' for recreational dives within NDL limits.

The two most important things in reducing the risk of DCS is to increase the PPO2 and compress the bubbles. A depth of 33' doubles PPO2 and compresses bubbles in half. That is often enough to alleviate symptoms from much deeper dives when administered quickly. Bubbles in the bloodstream almost always exist after any dive, but are small enough that symptoms don’t present or we just can’t find them with instrumentation.

I often return to 15-20' as a prophylactic measure after a deep dive, often in less than 10 minutes of surfacing and on pure O2 if available — but air or Nitrox is just fine when it’s not.

IWR has its place, but only under well prepared conditions and when the nearest operational chamber is many hours or days away.

In-water Recompression | Rubicon Foundation
 

NAM001

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I have no real clue what protocol says about this. My opinion is you should be able to go back to the missed depth. there is a process that says what to do with a missed or not completed deco stop. you could follow that if you want , but the key to this is that a safety stop is just that a non required stop.

about a month in a half ago i had an exciting dive at verde island. after being pushed down to about 42 meters during descent before bringing that under control, the dive continued normally until the safety stop, by this time blown well off the reef into the blue. after a short time at 5 m was blown down to about 10 m (guess) before regaining the 5 m mark. shortly thereafter was pushed up nearly to the surface. descended again to 5 m and because the computer was treating this as a blown safety stop there was no further countdown. manually timed a 5+ minute stop at a relatively level 5 m before surfacing. post dive was normal, with no ill effects. same for buddy, who had nearly the same profile but maintained control at the safety stop somewhat better than i did.

question: once the safety stop is blown as this one was, does it do a body any good to descend to safety depth and resume/restart a stop? my instinct is once the cap is off the bottle any benefit from regaining depth is marginal at best, but i don't recall seeing this issue discussed before, even though i assume it is a relatively common experience. please forgive me if i didn't search hard enough for an answer before posting.

r
 

xrcjdx

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thanks all for the time and thoughtful answers.

@pearlman - i'm not sure of any names there except north and south. the washing machine u r talking about is just east of sabang, correct?
 
https://www.shearwater.com/products/perdix-ai/

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