Descend to Decompress???

[BlaineAtk]

I am sure this has been covered on here before but I couldn't seem to find it, I was sitting back thinking about if for some crazy reason you shot up from the bottom and you were fairly deep and had been down close to your time limit at certain depth. I was wondering what the consequences would be of going back down and starting your offgassing or decompressing at a depth a little above your average depth for the majority of the bottom time? Now, while I was thinking about all of this I came up with a couple different "answers" in my head, both of which could be completely inaccurate which is why I wanted to come to the forum. My first thought was that if you were diving air you would more than likely end up loading more nitrogen and possibly make a rough situation worse....... maybe you wouldn't have enough bottle to even touch the required obligation, I don't know... hopefully someone can chime in here on this! My second thought brought me to the idea that if you had been diving air for your dive but had a nitrox bottle onboard with you and switched out and went back down, you could go down to a safe depth for your mix and start the decompression there and work your way up from there making a few stops every 5 - 10ft with the extra oxygen. Would this help your situation or still make it worse? Obviously, the overall best option is to get to a chamber as quick as you can, but in this thought I was having, the situation had you a long way from a chamber....

Anyway guys, Im sure with this question you can tell that I don't know a whole lot about decompression theory or if that even applies to my question. Any added input would help give me one less thing for my mind to wander and think about before I go to sleep hahah

So thank you guys and Hope to get some decent answers!

 

[racerx_]

There were some threads about this but can't remember where they all are.. although some people do this, the general consensus seems to be that its not a good idea. I think one of the reasons was that unless you have specific calculations, surface support and the right gas you're more likely to do more harm than good and are probably better off on 100% O2 and then in a chamber if necessary. As you mentioned you would be ongassing nitrogen if your diving with air.. again that's my vague recollection.

Most of the instances I've heard of where people did it, seemed more of a panic response than any specific decompression plan



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[Lemna]

It's called 'in-water recompression', and I don't believe many agencies advocate this (anymore) for recreational divers. Seems much safer to use pure oxygen at the surface while you are waiting for emergency services. It's described in the navy diving manual though, but these guys have support divers and most likely surface-supplied gas. By the way, the main problem would not necessarily be the time you spend at depth, but the speed at which you ascend.

If you are looking for a good read on decompression theory, try 'Deco for Divers' by Mark Powell. There is also the very interesting 'Ask Dr. Deco' forum here on ScubaBoard.

Others will probably chime in with better answers...

 

[supergaijin]

In the old days, if you came up bent, you were obliged to try to go down again and recompress the bubbles. Diving was a bit different back then- usually deeper but shorter dives, far away from any help.

Nowadays this practice is ill-advised. You're more likely to be better off hauling ass to the nearest source of oxygen and then a chamber. Recompressing underwater following typical mulit-level and repetitive dives woud require a massive amount of time underwater- not recommended.

 

[danvolker]

I am sure this has been covered on here before but I couldn't seem to find it, I was sitting back thinking about if for some crazy reason you shot up from the bottom and you were fairly deep and had been down close to your time limit at certain depth. I was wondering what the consequences would be of going back down and starting your offgassing or decompressing at a depth a little above your average depth for the majority of the bottom time? Now, while I was thinking about all of this I came up with a couple different "answers" in my head, both of which could be completely inaccurate which is why I wanted to come to the forum. My first thought was that if you were diving air you would more than likely end up loading more nitrogen and possibly make a rough situation worse....... maybe you wouldn't have enough bottle to even touch the required obligation, I don't know... hopefully someone can chime in here on this! My second thought brought me to the idea that if you had been diving air for your dive but had a nitrox bottle onboard with you and switched out and went back down, you could go down to a safe depth for your mix and start the decompression there and work your way up from there making a few stops every 5 - 10ft with the extra oxygen. Would this help your situation or still make it worse? Obviously, the overall best option is to get to a chamber as quick as you can, but in this thought I was having, the situation had you a long way from a chamber....

Anyway guys, Im sure with this question you can tell that I don't know a whole lot about decompression theory or if that even applies to my question. Any added input would help give me one less thing for my mind to wander and think about before I go to sleep hahah

So thank you guys and Hope to get some decent answers!

What the agencies fail to mention, is that it normally takes 1 to 2 minutes for hypersaturation to occur... actual bubbling is DCS. If you had a sudden explosive ascent, by accident, and you were able to fix the cause of the inflation problem, whatever, in a few seconds at the surface, you could still easily have time to rocket back down to your previous depth, and do a very slow ascent with multiple stops....When I say rocket, I don't mean swimming hard, as that could cause bubbling by itself--I mean dumped BC and falling fast with some kicking too, but not a hard effort.


The AGENCY ISSUE is that if you wait too long, hypersaturation will have already begin, and bubbles will be popping out of your bloodstream and growing. The Agencies assume you do not have 100% O2 to get this to resolve, and even for a tech diver, the issue becomes "how badly is the blood flow impaired, when the tech diver attempts to go back down". If it is impaired too much, the attempt to begin resolving the bubbles may fail due to extreme damage done prior to the attempt to go back down, and inflamation and other issues beginning to result....again, the whole issue is moot, if you INSTANTLY go back down from the sudden ascent.

This may fail if the ascent in question was not a rocketing ascent accident, but instead, a slow ascent00but one where stops were omitted, and lots of time elapsed where bubbles began growing and blocking circulation. Damage would already be done, so this is a much more complicated issue, much closer to what the agencies are "speaking to" with their recomendations. It might resolve with in-water recompression.....and with pure O2, there would be many situations where it could resolve...but in most cases, the people that could handle this, and that carried the O2 and had the training for this, would not have the type of accident where this would be necessary.

The stuck inflator that a diver cant get to in time, to pull off the hose and end the inflation, is about the only scenario that comes to mind where the type of rocket ascent of a "good diver" might then call for that same diver to finally succeed in getting the inflator hose detached, and then to rocket back down.

 

[spectrum]

I agree with all that have discouraged the practice of in water decompression. In many ways it can and will work. but it has a few gotchas
1) The diver is apt to be cold while doing so and that does not promote good off-gassing
2) Chamber rides usually include optimized gasses whereas in the water would probably only offer air, lengthening the process elevating the risk of #1
3) It's an inexact art at best and if it goes sour being down in the water column on a scuba regulator cold and tired you have a big chance of major complications.

That being said as in the day if you are truly remote to a chamber, have no O2, feel you are at risk of DCI / getting bent it's a ditch effort.

Pete

 

[danvolker]

I agree with all that have discouraged the practice of in water decompression. In many ways it can and will work. but it has a few gotchas
1) The diver is apt to be cold while doing so and that does not promote good off-gassing
2) Chamber rides usually include optimized gasses whereas in the water would probably only offer air, lengthening the process elevating the risk of #1
3) It's an inexact art at best and if it goes sour being down in the water column on a scuba regulator cold and tired you have a big chance of major complications.

That being said as in the day if you are truly remote to a chamber, have no O2, feel you are at risk of DCI / getting bent it's a ditch effort.

Pete

Pete, I would agree with you, except for the bonafide "good diver" rapid accident ascent scenario I described above......in this scenario, you could prevent all damage of DCS from occurring....waiting for the chamber WILL GUARANTEE some damage, even if it is damage that can heal. Another scenario for this....you are on a deep ( 140 foot dive) and find a diver from another group from your boat, lying on the bottom unconscious--you have been down 10 minutes or more already. If you know the boat is likely to be near overhead, follwing your group's flag or buoy, then you"could" do a rapid ascent with the unconscious diver, inflate their BC as you near surface, SEE that the boat sees you and the EMERGENCY in the 10 seconds you are at the surface, then leave the diver on their back at surface ( hopefully with reg in mouth) and head straight back down--let the boat take over the rescue....With some boats and crews in Palm Beach, this would be a perfect rescue-- they would see you and be on you in seconds...and a crew member would be doing the cpr etc long before you could have done any thing due to being geared up.

We are talking very specific instances here....But the understanding of the issue of DCS does call for making real distinctions like this...and what moral responsibilities exist.

 

[BlaineAtk]

Thanks for the replies! I have been thinking about it for a little while now and I knew that the situation would be HIGHLY UNLIKELY to happen, if it did, it would be an avoidable situation anyway by simply not putting yourself in it. Although, you could still have the emergency of the stuck inflator and that could be an issue but you should be fluent enough with your gear to hopefully alleviate the issue before it becomes a problem. So from what I am gathering, it would be best to just get to 100% oxygen asap and get to a chamber. I will most likely purchase that book and read up on it.

 

[elan]

My instructor answered this as follows:
- if you have access to EMS and the chamber in reasonable proximity call EMS so they can take you to the chamber.
- if the chamber is thousand miles away then do the in water recompression with the highest o2 gas available as long as you can but having someone going down with you to watch you.

 

[PfcAJ]

Consider what would happen if you attempted an IWR and went symptomatic while in the water. Bad news...