Deco Procedures

[VTWarrenG]

newton,

I don't have any basis for the number 90% -- my apologies for presenting it as fact. It was an educated guess.

- Warren

 

[Lost Yooper]

I'll just briefly go through some of these.

Originally posted by newton
I know you should never deviate from your plan, but sometimes stuff happens and it's time for Plan B.

LY mentions he has some tables for different depths and times, but what happens when you stay down too long (found a great relic, got silted out in a wreck, O-ring blew, etc..)

As I understand, the tables are generated with certain assumptions (depth and time), and when you violate one, the table is no longer useful. (True?)

It's useful when you combine it with what's in your head. Once you understand what you are trying to accomplish with the bubbles, it's relatively easy to make an educated guess of what to do.

Example:

The plan is 240' for 40 minutes, and I have tables for this. However, I found a porthole, and I stay down for 45 minutes, longer than my table is setup to do.

What now? Obviously, (at least to me), pre-calculated tables can't take into account all of the different possibilities there are.

I'm guessing the answer to this question is

"Don't do technical/deco diving unless you are absolutely committed to your plan, and do not deviate from it."

I can see alot of really good arguments for this, and any budding technical diver *must* be willing to follow these rules to the letter.

Discipline is apart of it, but things happen. I have a few sets of contingency plans that I carry for various circumstances. In your particular example, 5mins isn't all that relavent -- I would just hang for a little longer and add a minute to my final ascent time. Remember, deco isn't an exact science that is accurate to the minute.

However, when I read about the WKPP divers going down into the caves they have *NO* idea how long they are going to be under when they are extending the line. GI3 has a some-what famous post where he talks about extending the line from 14K to 18K. Prior to the dive, he had no idea how long he was going to be down, so how can you plan for such a dive? Do you generate saturate tables for the maximum depth and use them? (I don't think so, since according to the articles I'm reading, even the dives the WKPP folks are doing aren't saturation dives).

They are very close to saturation diving. Once you've gotten to that level, the deco is pretty easy and standard. Their understanding of deco is so acute, that it's quite fascinating (at least to me). Irvine doesn't even take tables with him any more, so go figue.

Later.

Mike

 

[newton]

I'm enjoying this.

[ The plan has been violated, and the tables are no longer valid ]


As I understand, the tables are generated with certain assumptions (depth and time), and when you violate one, the table is no longer useful. (True?)

It's useful when you combine it with what's in your head. Once you understand what you are trying to accomplish with the bubbles, it's relatively easy to make an educated guess of what to do.


I imagine alot of that comes with experience and staring at generate tables. I have no experience with generated tables (except the standard non-deco tables for rec diving).


"Don't do technical/deco diving unless you are absolutely committed to your plan, and do not deviate from it."

I can see alot of really good arguments for this, and any budding technical diver *must* be willing to follow these rules to the letter.

Discipline is apart of it, but things happen. I have a few sets of contingency plans that I carry for various circumstances. In your particualr example, 5mins isn't all that relavent -- I would just hang for a little longer and add a minute to my final ascent time. Remember, deco isn't an exact science that is accurate to the minute.

Totally agree regarding the non-exactness of deco. My example of 5 minutes over was not very good since I was trying to find an example that had a big effect on deco, but was still within the realm of feasibility. (Again, my lack of experience/knowledge of deco tables shows..)

However, when I read about the WKPP divers going down into the caves they have *NO* idea how long they are going to be under when they are extending the line. GI3 has a some-what famous post where he talks about extending the line from 14K to 18K. Prior to the dive, he had no idea how long he was going to be down, so how can you plan for such a dive? Do you generate saturate tables for the maximum depth and use them? (I don't think so, since according to the articles I'm reading, even the dives the WKPP folks are doing aren't saturation dives).

They are very close to saturation diving.

Really? That's not the impression I get from the literature. What I'm reading implies that it takes days of diving to get saturated, which really only happens when you're in a dive bell or something like is used on oil platforms.

However, I suppose that if you treat the dive like a saturation dive, you certainly can't go wrong. (But, it would also explain why they're 'saturation-deco schedules' take alot less time than the ones used by commercial divers. They're not really saturated.

Irvine doesn't even take tables with him any more, so go figue.

That much is amazing.

 

[Lost Yooper]

Originally posted by newton

Right. Complete decompression depends on lots of factors, including the length of the surface interval. As far as I know, the current thinking is that you should be completely off-gassed 24 hours after you get out of the water from doign recreational (aka non-deco dives). Does that hold true for tech dives as well?

Of course, it depends on the person. It is my understanding that a person who is in relatively decent shape; uses a good trimix; incorporates proper deep stops/slow ascents; uses proper deco mixes; follows a good planner; incorporates a slow final ascent; is well hydrated; has no preconditions; and avoids post dive stress, they should be offgassed somewhere between 1-6hrs or so. Of course, this is all subjective and has little to no scientific backing that I know of. This is only my understanding. The "current thinking" has no choice but to encompass everyone from the very physically fit to very obese divers, I guess.

Unless your GI3, who likes to do the last 20' bubbling, according to the talk he gave the Dutch (??) where you posted the MP3 a couple weeks back. However, I'm more interested in what normal people do, and I don't consider George 'normal' .

Normal people who are using computers (and aren't using deep stops) are doing a lot of their deco by bubbling -- which is less than optimal. What he's talking about is getting rid of nitrogen in solution deep (using slow ascents and proper deep and intermediate stops), and using the shallower stops (on 02) to get rid of nitrogen in bubble form -- which is very efficient.
When you hit the shallower depths, the nitrogen bubbles will start to come out. This is why it is critical to ascend slowly during that final ascent -- so your lungs can filter out the bubbles. If you ascend too fast, the lungs won't catch all the bubbles. No matter what you do, once you surface you will get a shower of bubbles -- this normal. The difference is in the amount and the severity.

That's my understanding, anyway.

/]So, in these kinds of cases, it wouldn't be advisable to use 'standard' tables, but instead either bring you Deco laptop with you on a trip, or plan the trip ahead of time, and *stick* to the trip. Is this a fair assumption? (It would seem to me that this would be overly restrictive, since when doing a trip like the Doria, you don't have a lot of control over things like surface intervales, since that is often dictated by the weather as well as your boat-mates).

I would bring my lap top for sure.

Mike

 

[newton]

Unless your GI3, who likes to do the last 20' bubbling, according to the talk he gave the Dutch (??) where you posted the MP3 a couple weeks back. However, I'm more interested in what normal people do, and I don't consider George 'normal' .

What he's talking about is getting rid of nitrogen in solution deep (using slow ascents and proper deep and intermediate stops), and using the shallower stops (on 02) to get rid of nitrogen in bubble form -- which is very efficient.

Effiecient I'll believe. However, it doesn't sound very safe.


When you hit the shallower depths, the nitrogen bubbles will start to come out. This is why it is critical to ascend slowly during that final ascent -- so your lungs can filter out the bubbles. If you ascend too fast, the lungs won't catch all the bubbles. No matter what you do, once you surface you will get a shower of bubbles -- this normal. The difference is in the amount and the severity.


This make alot more sense now that you've explained it. I'm not sure I like artificially causing the nitrogen to bubble (since it sounds like something you want to avoid), but I can understand the effeciency argument.

From the talk he gave, I got the impression that the last 20' stop and slow ascension gives him the greatest bang for the buck in terms of decreasing his deco times vs. the tables generated by DecoPlanner and other 'newer' deco programs.

It just sounds unsafe from my point of view, since it even contradicts even some of the more aggressive/newer deco software.

In any case, I'm enjoying the discussion alot, since I'm learning something.

(Wonder if UP will chime in here with his wisdom....)

 

[Lost Yooper]

Originally posted by newton

(This is especially important when you discuss things like flying after diving. Many of the current WKPP/DIR folks believe that you should be able to dive moments after doing a deco dive, which I believe to be utter foolishness. It's their life to do as they please, but I'd hate to be on the same plane if one of them had a DCS hit during a flight.)

This is some of the more unusual things they do that are very much against the grain of the industry as a whole. Irvine talks about a time where he and Bill Mee were diving deep in the Bahamas and flew home in a small Sesna at 10,000' while still in their wet shorts -- never had so much as an itch. Science doesn't always have all the answers. Personally, I don't care much about flying after diving considering the cabin is pressurized anyway -- that's just me though.

Actually, this is fairly common. Many of the articles on decompression theory explain this as well. It's not rhetoric so much as the lingering effect of our previous lack of knowledge in understand deco theory. When in doubt, be more conservative, especially when it comes to your life.

The last I heard, they aren't even sure who came up with the "reverse profiles is bad" thing. It seems to have come about out of thin air with out much thought put into it. It seems to be a non-issue.

We're in violent agreement, although I'm more convinced from the deco papers from the mid-90's than in GI3's experience.

GI3 and the WKPP folks are not what I consider to be 'normal'. They are in *way* better shape than most recreational divers, and in better shape than even most technical divers. They have a heavily regimented lifestyle (most, if not all WKPP divers are vegans), and Doppler studies of GI3 show that at least he is more resistant to DCS/bubbling than the average diver. (This could be related to his lifestyle, genetics, or the phase of the moon, but at this time we really don't know why).

Applying his experiences to the rest of the world w/regard to deco (something that varies from day to day in an individual, let alone the variations across individuals) is something that shouldn't be done lightly. Just because he can deco in half the time that the Navy tables doesn't mean his tables are better.

On the other hand, neither can his experiences be ignored, and what I'm seeing in the literature is that their *results* aren't being ignored. They are pressing the envelope and their experiences are causing experts to re-examine some of their assumptions to try and explain
why these folks aren't getting DCS.

IMO, the answer is a combination of personal physiology, experience, and a little bit of luck.

Keep in mind, that it's not just him doing this stuff. He requires his deco theories to be followed by his members too. They are all coming out pretty good -- though not as good as he is.

I have little doubt he has a better handle on this stuff than the Navy tables. In fact, the Navy has been studying these guys for years.

An interesting time? Most certainly .

Mike

 

[Lost Yooper]

Originally posted by newton

This make alot more sense now that you've explained it. I'm not sure I like artificially causing the nitrogen to bubble (since it sounds like something you want to avoid), but I can understand the effeciency argument.

From the talk he gave, I got the impression that the last 20' stop and slow ascension gives him the greatest bang for the buck in terms of decreasing his deco times vs. the tables generated by DecoPlanner and other 'newer' deco programs.

Avoiding bubbling would be great, but is unrealistic. Bubbling is a part of deco in the shallows. The difference is in how you deal with it. If you follow Deco Planner and shoot to the surface following your last stop, you'll be fine, but you'll be a whole lot better if you took 3-5mins to get to the surface (getting rid of more bubbles). What he is talking about, I believe, is that he can deco out quicker than any of the planners because he shaves off times the planner spits out by using the very slow final ascent. I don't do any shaving. I do what the planner says plus add in the slow ascent.

(Wonder if UP will chime in here with his wisdom....)

I hope so. There's guys on here who know more about this crap than I do. Besides that, my fingers are getting tired .

Mike

PS. You should get on Tech Diver and do a search for deep stops, helium, deco, and other relavent terms and just read through those discussions. You'll have to wade through a lot of BS and profanity, but there really is some good stuff to be had on there. It beats the heck out of getting it second hand, I think. This is fun though .

 

[AquaTec]

Newton
I am going to jump in here, and try and catch up.

Deep dive first or repetitive diving, decompressing is the same either way [I think]
As long as you figure for it in your method of doing dive planning, I use software that will account for repetitive dives or reverse profiles. I do agree that at the completion of your deco you have eliminated a large percentage of the inert gas. And as soon as you do another jump then you are starting to load up exponentially, so it would seem that the relatively small amount remaining even though it needs to be figured in plays a small part in your next dive.

Your five-minute over thing I don’t agree with Yoop [which may be the first time].
This is completely relative to the depth and PLANNED time of your dive
For instance take a dive of 300 ft for 15 minutes = total RT of 87 minutes
Add five minutes to that bottom time [all other factors being equal] and now your run time is 128 minutes that’s 50% more time. Gas planning and management now becomes a major issue, even if you are able to calculate your new deco stops and times from memory.

The software I use [Voyager] has one big draw back it doesn’t figure deep stops automatically, but one of the benefits is that it generates dive tables that show your planned dive time and depth and then ten minutes and ten feet either side of that. I just laminate and carry along.
I also carry my bailout deco stops for the planned depth and time. Which will include loosing gas from various deco, travel, or bottom mixes. I am know to be a diver who follows my tables very strictly, were other buddies are a little looser on them.

I believe that deco is not an exact science, and that there can be fluctuation either way within your own physiology that day on that dive. I feel that the deco tables mean average of those variations so I try to stick to them. Supposedly hitting the middle ground on how my body is reacting to the days diving.

I agree with you that we need to be careful that we don’t just follow what one particular group of supper divers are doing, because of the reasons you pointed out, unless we can say we fit into their physiological state.
Its like the old argument about the navy tables [which is the only tables I ever memorized some 20 years ago] if you are a navy seal or experimental dive unit member then make full use of those tables, if not get realistic.

Your comments about ascent rates Yoop has dealt with this well, I will just add the old first grade example. Dump about an inch of coke from a bottle then shake it up, through it across the room. Now untwist the top extremely slowly, if bubbles form that’s ok, if bubbles start to overflow out the cap then your headed for the chamber. This is an exercise in patients and discipline, which will be required when you are ascending during deco.

 

[Lost Yooper]

Yes, that's right. It is dependant on depth and planned time. This is why a contigency plan should be brought with you to account for such over extentions.

Good catch, Doug.

Mike

 

[WYDT]

Decoplanner has a cool feature where you can print a deco range with your own parameters for depths and mixes.

I printed out a set for 32% & a set for 34% (what I use on most N FL cavedives) that start at 60ft and go to 120 in 10min increments starting with 1min deco @ 20ft. One set with O2 and one without O2 for deco.

I then wrote in big letters (without obstructing the numbers) the mix and if it was WITH O2 or not. Then cut into 2 pieces (so they would fit into my wetnotes) and had them laminated at the local mailboxes etc. 34% WITH O2 on one side and 34% WITHOUT O2 on the other. Same for 32%.

They now have ~20 dives on them and still look brand new.

So what you have is not one plan but every scenario you can think of right there in one table.

If you use the same mix all the time you will memorize this table pretty quickly (took me about 5 dives) and not even have to take it out anymore!

I'm a BIG fan of keeping it simple!