BSAC 88. Time for an update? [Archive] - BSAC Scuba Diving Forums

Matt Duke

20-10-2003, 14:35

Hello,

Put simply, all the PC and wrist mounted decco software I have, seem to give much longer deccompression penalties for dives, than the 88 tables.

Are these new programs "Ultra safe" (i.e don't sue me) or has deccompression theory moved on, and the resultant decco algorithms more accurate than the 88 Tables?

I guess that 15 years is a very long time for tables to have been used, and wondered if there was any plan to "Update" them at HQ?

If there isn't a plan to update them, what does the club think about this issue?

I have to say, that I have not met anyone who actually uses the 88 Tables for anything other than teaching "Club Divers", or having in their BCD as a backup for their computers.

"Flaming" or "Anti-BSAC" replies to this are not welcome, nor the intention of this post. I simply think that the time has come to debate the use of "88 tables" in the BSAC. At the same time, change is a challange. The implementation of the BSAC 88 tables caused some discontent within the membership, so I imagine this proposal will do the same.

Kind Regards,

Matt Duke
Bergen, Norway

Chris Cherrington

20-10-2003, 18:46

Hello,

Put simply, all the PC and wrist mounted decco software I have, seem to give much longer deccompression penalties for dives, than the 88 tables.

Are these new programs "Ultra safe" (i.e don't sue me) or has deccompression theory moved on, and the resultant decco algorithms more accurate than the 88 Tables?

Matt,

Check out the recent in-depth forum for more stuff on the 88 tables. The short answer is that the new stuff is different thinking and arguably more conservative on dive 1 and less so on repetitive dives.

Personally I cannot see a point in 'updating' the tables as most of us now use computers not tables to dive with and BSAC recognises/accepts Bulhmann and derivatives. Tables are OK to learn on and if you cannot afford a computer. The 88s are easy to use and introduce the concept of run time which is great when you get a bit more advanced. Whether they should form such an integral part of training and exams for DL, AD and FCD is more open to argument.
Also it depends what you mean by updating. If you accept they work (i.e. you don't get hit) then they don't need it. Updating for mixed gases is a different thing and no doubt someone is looking at this for BSAC Trimix if/when it arrives.

Chris

Steve Walker

20-10-2003, 19:22

:=Hello,
:=
:=Put simply, all the PC and wrist mounted decco software I have, seem to give much longer deccompression penalties for dives, than the 88 tables.
:=
:=Are these new programs "Ultra safe" (i.e don't sue me) or has deccompression theory moved on, and the resultant decco algorithms more accurate than the 88 Tables?
:=

Matt,

Check out the recent in-depth forum for more stuff on the 88 tables. The short answer is that the new stuff is different thinking and arguably more conservative on dive 1 and less so on repetitive dives.

Personally I cannot see a point in 'updating' the tables as most of us now use computers not tables to dive with and BSAC recognises/accepts Bulhmann and derivatives. Tables are OK to learn on and if you cannot afford a computer. The 88s are easy to use and introduce the concept of run time which is great when you get a bit more advanced. Whether they should form such an integral part of training and exams for DL, AD and FCD is more open to argument.
Also it depends what you mean by updating. If you accept they work (i.e. you don't get hit) then they don't need it. Updating for mixed gases is a different thing and no doubt someone is looking at this for BSAC Trimix if/when it arrives.

Chris

I tend to agree, no need for a new set and all the work that would entail; tables/puta's etc all use "models" and AFAIAC a model is a model is a model... Personally, I never do only the minimum required by table/puta's any way, so I'd say for anyone with concerns over BSAC'88 safety levels, whether justified or not, - stick in the three minute safety stop at 6m as a matter of course

Vic

20-10-2003, 20:28

> Personally I cannot see a point in 'updating' the tables as
> most of us now use computers

I actually disagree with this.

Most of us use a Buehlmann algorithm, whether we use tables or computer. Why? Is Buehlmann better? No, it's just more accessible.

I'm a big fan of the BSAC '88 tables. They are the simplest table system you'll find - ever. I'm not too convinced about the numbers on the tables though - particularly in light of more modern thinking about ascent rates, etc.

I'd really like to see the model published in a parametric form so that we can play about with this sort of thing - I'm not sure that's going to happen, but Tom Hennessy has very kindly sent me some info on the model, so I'm hoping to find the time to put something together. If I ever get round to it - and if I get it right! - we can start looking at how the model scales in comparison to the Buehlmann model. That could be fun ;-)

Vic.

john kendall

20-10-2003, 22:16

Matt Duke

21-10-2003, 10:04

I believe it would be forward thinking of BSAC to commission some tables that take into account modern thinking on deep stops, rather than just "Bend them and Fix them" tables.

John

Which is where we need to find out if it's "Worth it" from a cost benefit perspective? I also have had a much better experience by using Pyle stops, which is one the factors that made me post.

So, back to the 88. The options as I see it are:

1.) Do nothing, continue to promote BSAC 88 as a good safe tool.

2.) Commission a new set of tables, perhaps based on a "Known" algorithm, with a nice setpoint with plenty of the "J" factor.

3.) Take the 88 Tables out of circulation, and use a thrid party set of tables as the "Chosen" BSAC option for teaching and diving.

I honestly think it's time to debate this.

Matt

Keith L

21-10-2003, 10:16

[Personal Opinion]

I have to agree with Matt D on the actual usage of the BSAC-88 tables, like many I teach them (I also agree with Vic ? they are probably the easiest tables to teach and use) but I do not use them in my own diving. I do not in any way believe that they are unsafe, but with my limited understanding of modern decompression theory they do not fit very well with my preferred style of diving. There are two aspects of the BSAC-88 tables where I feel that revision could be due, this is simply revision to cater for modern diving practices ?

Ascent Rates : One of the strengths of the BSAC-88 tables is that they are a run-time table rather than a bottom time table. But that strength could also be seen as a weakness with the medical evidence and modern practices tending towards slower ascent rates and the use of deep stops. I will not ascend at the 15m/minute required by the BSAC-88 tables, 5m/min on the shallower part of the ascent is more like it for me, I do use 2 minute deep stops and like many others I find that this cuts down the post dive fatigue. Being a run-time table the BSAC-88 cannot give any credit for these slower ascent rates, to use slow ascent rates and deep stops with the BSAC-88 tables gives impossibly short bottom times and/or decompression requirements vastly different to other algorithms.

Surface Intervals : This is the difficult one, the strength of the tables is their simplicity but this simplicity is at the expense of flexibility in the very granular interpretation of the surface interval. I would venture to suggest that the majority of repetitive dives actually undertaken recreationally would have the diver in the C or B current tissue code. C persists for 2 hours, B persists for 10 hours! Whilst this may be sufficient for the traditional British 2 dives per day this does not fit very well with multiple dives per day as seen in some training situations and the trend towards modern liveaboard diving with three or sometimes fours dives per day.

I do fully appreciate that decompression theory is guesswork on the first dive and guesswork-on-a-prayer for repetitive dives, but multiple dives planned using alternative tables are safely carried out all of the time. These dives would be impossible on the BSAC-88 tables without harsh decompression penalties due to the course nature of the surface interval codes. For this reason I do not feel that the BSAC-88 tables fit very well with this pattern of diving.

I am not saying that the BSAC-88 tables are wrong in any way, far from it ? they have been used successfully for many years and have been proved to be a safe and reliable table. I am certainly no decompression expert, if I am wrong in any of my observations and practices then please tell me (keep it simple). But like Matt D I do not feel that the current BSAC-88 tables cater for all of our modern diving practices and needs, my personal table of choice is the Buehlmann as it is what my computer uses, it can be used with EAD and it can be used in all of the situations that I have described above. So maybe it is about time that we thought about updating the BSAC-88 tables to give us a table that can be used in all of the modern diving situations and practices?

Regards

Keith L

Chris Cherrington

21-10-2003, 10:39

I am not saying that the BSAC-88 tables are wrong in any way, far from it ? they have been used successfully for many years and have been proved to be a safe and reliable table. I am certainly no decompression expert, if I am wrong in any of my observations and practices then please tell me (keep it simple). But like Matt D I do not feel that the current BSAC-88 tables cater for all of our modern diving practices and needs, my personal table of choice is the Buehlmann as it is what my computer uses, it can be used with EAD and it can be used in all of the situations that I have described above. So maybe it is about time that we thought about updating the BSAC-88 tables to give us a table that can be used in all of the modern diving situations and practices?

Regards

Keith L

I agree with the comments made regarding the ascent rate. Most now accept 10m/min as max with a bit slower better. However, the question is cost vs. benefit. If the "update" were free then maybe, but I guess it would not be and there is the rub. Why spend money on a new table when you can download Drogon or V Planner for nothing?
If we are to spend money surely better to wait a while until something is available with "Pyle"/Baker stop thinking and multiple gasses? Maybe post it on the web - Keith in your members only section??
That would be something - leading from the front again - to borrow something from another post.

Chris

Keith L

21-10-2003, 11:18

[Personal Opinion]

Divers never cease to amaze me, they will spend a tenner on a couple of plastic clips to dangle bits off but not a tenner on a dive table to keep them safe! I do not use Drogon or V Planner, I wouldn?t know how and they are overkill for my personal style of diving. Neither do I take a PC onto a boat with me (OK, I may do sometimes), I certainly don?t have one in my BCD pocket. Neither should we be looking at an all-singing-all-dancing-any-weird-gas-going solution IMHO. What we are talking about here is a simple recreational table that can be used by all recreational divers all over the world in all situations. A simple bit of printed plastic sheeting in a dive bag is the best solution for that. If you want to extend the model used to mixed gasses and even a software product then fine, but that?s as an addition, for those who need it, to the basic recreational table. I think you will find that is what Matt D was getting at.

Regards

Keith L

Vic

21-10-2003, 11:44

> 1.) Do nothing, continue to promote BSAC 88 as a good safe tool.
>
> 2.) Commission a new set of tables, perhaps based on a "Known"
> algorithm, with a nice setpoint with plenty of the "J" factor.

IMHO, the above ought to be combined.

There is no reason to believe that the Hennessy algorithm is incorrect, rather that we want to add features to the ascent profile. In this respect, it is no different at all from the Buehlmann algorithm - which also gives you shallow stops as standard. The difference is in publication - there is enough knowledge about Buehlmann in the public domain that Baker and Pyle could add their modifications without exceeding the allowed tissue loadings (because they could be re-calculated). This is not (currently) true of the Hennessy model - at present, all deep stops would have to be considered bottom time, and that's going to put you off-table in a heartbeat...

But if we had a computational model - if such a thing is feasible - we could add Pyle and GF stops to our hearts' content. This would satisfy everyone...

Of course it remains to be seen whether this is a safe thing to do with this model - I can't see a reason why not, but that doesn't mean that the reason doesn't exist ;-)

Vic.

Vic

21-10-2003, 11:50

> A simple bit of printed plastic sheeting in a dive bag is the
> best solution for that.

Indeed it is.

And for those of us who already have a PC and a printer, a laminator makes that sheeting very easy to obtain... ;-)

Vic.

Steve Walker

21-10-2003, 11:57

> 2.) Commission a new set of tables, perhaps based on a "Known"
> algorithm, with a nice setpoint with plenty of the "J" factor.

The "J" factor...? que?

AS regards all these algorithms, models, factors, theories, blah blah blah.... All the theory and maths in the world won't guard against the "H" factor, ie the human element, people wanting to cut corners, or in too much of a hurry to end the dive once they've seen the wreck or whatever.

If we (BSAC) were going to spend the type of time (and money!) needed to construct or adapt the current tables (which I find to be safe enough) I for one would like to see us (BSAC) encouraging more focus on intrinsic factors (ie fitness, diet, alcohol/tobacco etc) than on the extrinsic factors such as new tables, algorithms etc etc etc.

Chris Cherrington

21-10-2003, 12:57

[Personal Opinion]

Divers never cease to amaze me, they will spend a tenner on a couple of plastic clips to dangle bits off but not a tenner on a dive table to keep them safe! I do not use Drogon or V Planner, I wouldn?t know how and they are overkill for my personal style of diving. Neither do I take a PC onto a boat with me (OK, I may do sometimes), I certainly don?t have one in my BCD pocket. Neither should we be looking at an all-singing-all-dancing-any-weird-gas-going solution IMHO. What we are talking about here is a simple recreational table that can be used by all recreational divers all over the world in all situations. A simple bit of printed plastic sheeting in a dive..

Isn't that the one we already have?

If you only need a basic table then the 88s should suffice. If you want more then get a PDA/Notebook.

Did I miss something??

Chris
(Oceanic Divemax & Suunto Vyper BTW)

Keith L

21-10-2003, 14:54

If you only need a basic table then the 88s should suffice.

Do keep up at the back there!

Matt's original post alluded to the fact that the BSAC-88 tables are dated and may need updating, the question under disccussion is whether we should be doing this as a club. Even as a basic table they have their deficiencies in some peoples opinion. Also they are not easily (I believe) extendable in their current form into the technical diving realms.

So should we be looking at updating the BSAC-88 tables =AND= providing a model that could be extended into the technical realms? i.e. With a bit of tailoring could one size fit all?

Keith L

Matt Duke

21-10-2003, 15:53

So should we be looking at updating the BSAC-88 tables =AND= providing a model that could be extended into the technical realms? i.e. With a bit of tailoring could one size fit all?

Keith L

Thanks for spot on replies Keith. Good to keep the thread relevant.

The first thing I would like to establish, is whether the 88 Tables have now run their course, and if their use is no longer the safest option for our membership?

This question needs to be answered by a decompression expert, who is prepared to give independent advice on the subject to the BSAC.

But what do I (Or 99.9% of BSAC members) know about Decco? Nothing! I'm just a BSAC Advanced diver, who knows that in 1995 when we dived for a week in Scapa on Air, with no deep stops and a 15M/Min ascent I felt like crap all week, and from 1996 onwards having done similar dives with slower ascents, deep stops and Nitrox for the decco, I have felt really good after the dives.

So for me, a very personal subjective opinion is:

-88 Table Run times are not in line with my training from IANTD and TDI, and indeed even on the BSAC ERD course

-88 Table runtimes made me feel very tired and weak after diving a week in Scapa. One year later with slower ascents, Deep stops and EAN50 for the decco I felt great!

Now all this subjective stuff means nothing. It just explains why I have my own personal opinion based on my own personal experience. I am hoping that if lots of us have had similar experiences, then maybe the guys we elected to run the club might consider looking into this further?

Cheers

Matt
Bergen, Norway

Vic

21-10-2003, 16:00

> So should we be looking at updating the BSAC-88 tables =AND=
> providing a model that could be extended into the technical
> realms? i.e. With a bit of tailoring could one size fit all?

No, I don't think we should. The amount of time & effort it would take for BSAC to validate such tables is unlikely to be repaid in terms of fewer hits - there are already a number of solutions around to cater for those who want to put in deep stops, etc.

But at the same time, I think we should enable those who want to do it *for themselves* to do so; let's make the model public, and let people make their own decisions.

Vic.

rogersides

21-10-2003, 16:01

The first thing I would like to establish, is whether the 88 Tables have now run their course, and if their use is no longer the safest option for our membership?

Are there any details upon how many bends have occured using these tables?

Keith L

21-10-2003, 16:31

Are there any details upon how many bends have occured using these tables?

Such information is completely irrelevant outside of strictly controlled test conditions in all honesty. OK ? I get a bend, in one pocket I have my Buehlmann, in the other pocket my BSAC-88 ? which table bent me? I?ve also used ProPlanner in the past, perfectly within the tables ? and then sat outside the chamber watching my buddy being recompressed for doing exactly the same profile as me. Tables don?t get bends, people do ? or as it was very succinctly put to me by a chamber doctor ?bends don?t read tables?.

Safety is relative, the BSAC-88?s are probably no more or less likely to bend you than any other table. I am reminded of the guarantee that Greg Roach puts on his DivePlan software ? ?If you dive often enough, using this or any other model, you are *guaranteed* to get bent eventually?. That just about sums it up and that is the reality of the situation on ANY dive table. The only way to guarantee not getting bent on any dive table is to stay out of the water.

Keith L

Dominic Humphries

21-10-2003, 17:35

The only way to guarantee not getting bent on any dive table is to stay out of the water.

Unless you know that trick with the 88's multi-level tables and a chair, in which case you can get yourself into mandatory deco without going into the water :o)

Matt Duke

21-10-2003, 19:11

The only way to guarantee not getting bent on any dive table is to stay out of the water.

Keith L

That's right. But at the same time, would you(Take BSAC hat off) advise a diver doing a fairly typical "Advanced BSAC" dive of say 45M, with 10 minutes of stops, to:

1.) Use the BSAC 88 tables, and ascent rates with no deep stops

or

2.) Advise them to use a modern Dive computer, with a PC/PDA generated table bailout in their BCD pocket? (Assuming a slow ascent and deep stops.)

I can't help but feel the safer option would be number 2.

If it is number 2, then why are we teaching/allowing divers to do such dives on the BSAC 88 tables?

That's why we need to know if the table model still holds up in light of the last decade's research into DCI. If it does, then great. If it doesn't then I suggest we drop it.

/Matt

matt

22-10-2003, 00:59

Hi Matt, Keith, all

Thought I better stick my oar in.

First off I agree the best thing about 88s is that they are remarkably easy to use and teach. This makes them more approachable than RNT based tables and you have a chance that the less experienced will actually use them to plan dives. I also happen to like the enforced surface interval, it teaches the less experienced to be conservative. An extra 20 mins surface interval could make the difference between bent/unbent if the ascent gets out of hand.

For the benefit of those that rely solely on dive computers I personally think your mad. You are exposing yourself to a non-breathable atmosphere which has the potential to put you in a wheel chair and your going to do it without knowing before hand how long you expect to stay!!!!

Anyhow things I don't like about 88s.

Most obviously while there is plenty of disagreement in deco research slowing of ascent rates and the importance of safety stops are widely agreed on. Less well known but also in general agreement is that the last stop should be at 5.5m or shallower. The 88s are out of date in this respect.

Next we have the difference with Buhlmann tables. This one is rather odd as neither can be said to be more accurrate than the other, they are different guesses at the same problem. Both tables roughly agree on the time before you go into deco. What they disgree on is the length of the stops once your into deco. The only conclusion you can make is that for a first dive the Bhulmanns are more conservative than the 88s because they require a significantly longer stop.

So lets assume that both algorithms are equally safe. Why might we think about abondaoning 88s. Well what about the practical aspects.

Bends happen more frequently on first dives. Most likely because we do our long deep dive first. The publics attitude to helo evacs, coupled with modern equipment and divers willingness to spend longer in the water than in 88, makes a more conservative first dive somewhat desirable.

We have heard that 'everyone uses a computer'. Well those computers are almost exclusively using a Bhulmann algorithm. Try planning a dive on 88s and completeing it with a Bhulmann computer. Your slate bares no resemblance to your actual profile, lets hope you were generous with your air reserve! Now go do your BSAC nitrox course. You are taught to use a NX computer and take a slate...but you need a different slate for every possible mix and bottom time combination!

I do not apologise for what may appear a radical view. Is there a better way?

Well how about this. Retain the 88s as a no decompression table. Adjust the ascent rate to 10m/min and enforce a safety stop of 3 minutes at 5m or shallower. The adjustment needs no more than a reprint as it fits inside the current table. When the diver gets a computer the no stops times will roughly agree.

For decompression diving we abandon 88s and embrace the Bhulmann table. We could even publish a set with BSAC written on them. For Nx we use a Bhulmann table and teach EAD. So you only need carry one submersible table and write down the EAD, to back up your computer whatever the dive.

I feel this would both bring our techniques up to date and provide a clarity of thinking to our decompression practice. Unfortunately I doubt I will live to see such a change :-(

Just my 5ps worth

matt

22-10-2003, 01:35

:=> 2.) Commission a new set of tables, perhaps based on a "Known"
:=> algorithm, with a nice setpoint with plenty of the "J" factor.

The "J" factor...? que?

AS regards all these algorithms, models, factors, theories, blah blah blah.... All the theory and maths in the world won't guard against the "H" factor, ie the human element, people wanting to cut corners, or in too much of a hurry to end the dive once they've seen the wreck or whatever.

The sad fact is that AFAIK the vast majority of bends are caused by 'H' factors that have nothing to do with decompression practice; rapid ascents, running out of air, bad buoyancy and basic ignorance. However this is no excuse for teaching an out of date table to those who do manage to complete their profile's acceptably.

If we (BSAC) were going to spend the type of time (and money!) needed to construct or adapt the current tables

Here we almost agree. A complete re-write would be expensive and still not adress the problem that the table we end up with would have no resemblance to the algorithm computer manufacturers use.

(which I find to be safe enough)

Please tell me how you explain away 15 minutes of stops to someone that asks why their computer requires so much more decompression? People are concerned about this. I find that it is often the first time they venture to question BSACs wisdom. People want to be as safe as they can be.

I for one would like to see us (BSAC) encouraging more focus on intrinsic factors (ie fitness, diet, alcohol/tobacco etc) than on the extrinsic factors such as new tables, algorithms etc etc etc.

Yep agree, despite being a smoker that likes a drink and is not adverse to two 30-50m dives a day. I know my weakness and try to compensate in all other areas.

Chris Cherrington

22-10-2003, 10:13

Well how about this. Retain the 88s as a no decompression table. Adjust the ascent rate to 10m/min and enforce a safety stop of 3 minutes at 5m or shallower. The adjustment needs no more than a reprint as it fits inside the current table. When the diver gets a computer the no stops times will roughly agree.

For decompression diving we abandon 88s and embrace the Bhulmann table. We could even publish a set with BSAC written on them. For Nx we use a Bhulmann table and teach EAD. So you only need carry one submersible table and write down the EAD, to back up your computer whatever the dive.

I feel this would both bring our techniques up to date and provide a clarity of thinking to our decompression practice. Unfortunately I doubt I will live to see such a change :-(

Just my 5ps worth

Sounds like a reasonable compromise to me and low cost too. If you look at the PADI RDP it doesn't give much info on dives deeper than 24m but gives lots of granularity for the shallow stuff. Ideal for new divers on recreational profiles, useless thereafter - i.e. go get more training with IANTD/TDI (or BSAC even!!). The next level takes you to Bulhmann and all the software stuff for those of us odd enough to be interested in this area!

I think this is a good idea....

Chris

Matt Duke

22-10-2003, 12:25

:=Well how about this. Retain the 88s as a no decompression table. Adjust the ascent rate to 10m/min and enforce a safety stop of 3 minutes at 5m or shallower. The adjustment needs no more than a reprint as it fits inside the current table. When the diver gets a computer the no stops times will roughly agree.

In reality this is probably what actually happens. Divers wanting to do "Advanced" dives, tend to be encouraged to use Bhulman tables, and get ERD training.

So if this is the case, I agree, the BSAC tables should be recommended as "No-Stop" tables.

This in iteslf would be a positive move, if it is agreed that there are better, more current ways of working out ones decco obligation for advanced dives.

But again, without an "Offical" line, this is all just speculation.

So, in light of these postings, are the BSAC 88 tables under review then? Or not? If it's not something the committee are considering looking into then I think I've said my bit and will leave it at that. If they are, it would be great to hear.

Best regards,

Matt Duke

rogersides

22-10-2003, 12:59

Steve Walker

22-10-2003, 13:07

Please tell me how you explain away 15 minutes of stops to someone that asks why their computer requires so much more decompression? People are concerned about this. I find that it is often the first time they venture to question BSACs wisdom. People want to be as safe as they can be.

I dunno about that last line, I see/hear alot of people who try to cut every corner that they can get away with, but it's good to know there are others out there that are more safety concious than some folk I've seen. But to answer your question, I'd simply use that as an opportunity to reiterate the issue about "models", that no one model is perfect or necessarily accurate, that someone somewhere is always working on a new improved version, that models are there for guidance and are not absolutes in and of theirselves, etc, and most of all I'd use it to drive home the message that, when faced with differing levels of conservancy, you should always go for the _most_ conservative option, also I'd check to see if their 'puta was on a higher altitude setting ;-)

Cheers
Steve

terryh

22-10-2003, 14:39

But again, without an "Offical" line, this is all just speculation.

So, in light of these postings, are the BSAC 88 tables under review then? Or not? If it's not something the committee are considering looking into then I think I've said my bit and will leave it at that. If they are, it would be great to hear.

Just like to point out that commercial pressures have largely
been ingored in this debate.

We have a new Instructor manual, workbooks, Dive Manual etc.
which all spout 88's. True that only Sport & DL have any deco
elemenst, but that means the whole of this very expensive
reprint may need to be revised.

On top of that what of the contactual obligations with the
copyright owner (I presume intelectual property etc. belongs
to Tom Hennessy).

And finaly we have the current stock and/or reprints, printing
contracts etc. of the tables themselves.

If there is a true benefit to changing the tables then a long
term stratagy of change allied to the end of contractual
obligations etc. may be a less painful approach as long as
there isnt any safety compromise.

There is a larger picture. Of course safety comes first, but
we still need to be realistic.

TerryH

Matt Duke

22-10-2003, 14:52

There is a larger picture. Of course safety comes first, but
we still need to be realistic.

TerryH

Agree 100%.

So fingers crossed we will get an idea from HQ on what they think. Mind you, a public forum may not be the best place for this, but perhaps an "Offical position" would be nice.

Very interesting constructive comments from everyone. Thanks!

Best Regards,

Matt Duke

Keith Lawrence(BSAC)

22-10-2003, 16:31

:=There is a larger picture. Of course safety comes first, but
:=we still need to be realistic.

?but perhaps an "Official position" would be nice.

You cynics. Whilst I cannot speak for the NDC I can speak for myself, so if you want an ?official? position then here?s one for you ?

The day that Council makes a judgement along the lines of Terry?s speculation and basically says ??well, we know that we should really as it?s a safety issue but let?s get rid of all this old stock before we tell them? ? then that will be the day that an absolute minimum of one replacement Council member will be required.

If you knew what actually happens in Council and understood the way that we discharge our duties then you would understand why I find the notion of your speculation mildly insulting, no problem, you weren?t to know. But in matters of members vs commercial interests we ALWAYS side with the members. That sometimes makes things ?interesting? as we (Council) are both members representatives and directors of a large company, but ATEOTD we are the custodians of the club on behalf of the members and their interests come first. That?s what makes it such a damn difficult job at times.

I have never seen what you are suggesting Terry (and Matt) happen on Council, I haven?t even seen it get anywhere close. I can?t predict the future but I can tell you for a fact that it could only ever happen ONCE whilst I represented members on Council! I didn?t stand for Council to be party to decisions like that.

Cheers

Keith Lawrence
BSAC Council Member

terryh

22-10-2003, 17:54

:=:=There is a larger picture. Of course safety comes first, but
:=:=we still need to be realistic.

:=?but perhaps an "Official position" would be nice.

You cynics. Whilst I cannot speak for the NDC I can speak for myself, so if you want an ?official? position then here?s one for you ?

The day that Council makes a judgement along the lines of Terry?s speculation and basically says ??well, we know that we should really as it?s a safety issue but let?s get rid of all this old stock before we tell them? ? then that will be the day that an absolute minimum of one replacement Council member will be required.

If you knew what actually happens in Council and understood the way that we discharge our duties then you would understand why I find the notion of your speculation mildly insulting, no problem, you weren?t to know. But in matters of members vs commercial interests we ALWAYS side with the members. That sometimes makes things ?interesting? as we (Council) are both members representatives and directors of a large company, but ATEOTD we are the custodians of the club on behalf of the members and their interests come first. That?s what makes it such a damn difficult job at times.

I have never seen what you are suggesting Terry (and Matt) happen on Council, I haven?t even seen it get anywhere close. I can?t predict the future but I can tell you for a fact that it could only ever happen ONCE whilst I represented members on Council! I didn?t stand for Council to be party to decisions like that.

Cheers

Keith Lawrence
BSAC Council Member

I wonder sometimes if you ever really read my posts Keith.
Despite saying twice that safety IS the prime concern,
you chose to take it as an attack.

My post was simply stating that there are (as in just about
every decision made by BSAC) secondry issues.

At NO time was I actually being cynical or taking a pop at
BSAC. I was actually pointing out that BSAC have to do quite
a difficult ballancing act between safety and common sense.

As an example when did they decide to shred all the manuals as
soon as BB was banned? You mean they didnt!

No. They announced it at DOC told everybody via website/Dive
and even sent out emails via Regional Coaches. Eventually the
subject was removed from BSAC media when BSAC reprinted the
manual.

So there you have a prime example where the membership was told
that it was deemed unsafe to continue the practice, but a
common sense approach was taken so that a perfect servicable
(although now partilly incorrect) manual would not have to be
ditched.

Or how about changes to the recovery position and O2 Admin
changes. These were all changed with simple leaflets and
introduced into the next available reprint (New DTP).

Or how about Self-Declaration. If a medical was free, would
we have self-declaration? No. Then one (not all, I said one)
of the reasons/concerns must be financial.

I can continue across the board where there have been changes
throughout BSAC media and in no cases (that I am aware of) have
they been withdrawn. Updated, amended, informed of changes,
yes, but completly withdrawn. No.

BSAC's prime concern IS safety - no question wouldnt have it
any other way.
BSAC's secondry concern is logistics. How to implement/
introduce changes etc. Somewhere in there will be finance.
You might not like it, but it's real and it is there.

Rgds
TerryH

Keith Lawrence(BSAC)

22-10-2003, 18:48

Sorry about that Terry, there probably is an element of me taking it the wrong way. When you said ?If there is a true benefit to changing the tables then a long term strategy of change allied to the end of contractual obligations etc. may be a less painful approach as long as there isn?t any safety compromise.? that to me was stating the obvious and implying that we may somehow drag out any process.

You are perfectly correct in the examples that you gave, in ALL cases we just got the information out there the quickest way possible and sorted out the mess back at HQ later. (Dumping pre-printed packs, we did bin old stock rather than delay the new DTP in any way). I?m not sure about the contractual position of the BSAC-88?s, way before my time, but we?ve renegotiated contracts in the past. If it?s a safety issue then we would certainly work damn hard to find a way around any obstacles in the way of getting the information out there. That?s the way it should work, that?s the way it does work in my experience, personally I would never have it any other way.

I have no idea if the BSAC-88?s are up for discussion, well beyond by remit, but if they were then a proper project would be set up and everything would be considered. We wouldn?t rush it, but neither would we drag our feet in any way due to purely commercial concerns. Anyway, I hope that clears up that little matter. Accept my apologies and leave it there to continue with the real discussion?

Regards

Keith L

matt

22-10-2003, 23:51

Less well known but also in general agreement is that the last stop should be at 5.5m or shallower.

One of the things i like about the BSAC tables is the 6m stop. In practice i find it hard to do a 3m stop in swell, and on a recent dive two of our club's divers were brought to the surface from 3m in swell missing their remaining deco.

I hate hearing of incidents like this because they are so avoidable. If the swell is so bad that decompression is uncomfortable it is highly likely that the decompression is not particularly effective despite what your computers maths may say. A stable stop done a little deeper will do you more good than bobbing up and down in the swell zone. Holding a stop at 5m should be easily possible even in marginal conditions. Your computer will still clear at 5m, it will just take a little longer.

I did once have to complete deco at 7m when we started a dive in a F2 and ended it in a F6. I thought I was having a buoyancy mare until we surfaced in 4m to 5m of swell. Getting back on the boat was interesting.

Hope your friends were OK

Philip Smith

23-10-2003, 01:08

We have heard that 'everyone uses a computer'. Well those computers are almost exclusively using a Bhulmann algorithm.

Just to pick up on one small point in Matt's post, I doubt if the above statement is true, particularly given the popularity of Suunto models.

Philip Smith

matt

23-10-2003, 11:50

:=We have heard that 'everyone uses a computer'. Well those computers are almost exclusively using a Bhulmann algorithm.

Just to pick up on one small point in Matt's post, I doubt if the above statement is true, particularly given the popularity of Suunto models.

Strictly speaking your right Suunto use their own algorithm which uses (IIRC) 9 compartments compared to the Buhlmanns 8,12 or 16. The min and max half times look very similar, as do the m-values and gas rate. The ascent rate is the fixed 10m/min the Buhlmann table uses. The later models (Vyper onwards) add a limited RGBM which appears to add conservatism on provacative profiles.

I use a Suunto Stinger as a backup to my VR3 (Bhulmann) on single mix air and Nx dives. The difference in stop time is usually no more than a few minutes. The Stinger is a little faster for first dives and a little slower for subsequent dives. On U-profiles both computers are a little slower than the Bhulmann tables I carry. These comparisons ignore the additional 3 minute safety stop that the Stinger suggests.

The Vyper is the most popular computer amongst our clubs BSAC nitrox qualified divers. When we go diving they tend to want to borrow two things, my analyser and my Bhulmann tables.

So your right Suunto computers do not use a strict Bhulmann algorithm. But in practical terms a deco dive planned on Bhulmanns will be a lot closer to the Suunto output than a dive planned on 88s.

Chris Cherrington

23-10-2003, 13:21

:=We have heard that 'everyone uses a computer'. Well those computers are almost exclusively using a Bhulmann algorithm.

Just to pick up on one small point in Matt's post, I doubt if the above statement is true, particularly given the popularity of Suunto models.

Philip Smith

OK we are getting pedantic here!!!

There is no real Buhlmann algorithm as such and Matt's post (above) re. the Suunto is accurate as far as I know.

The "difference" is that the Buhlmann stuff is based around the M values concept, which (I think) originated from Robert Workman (USN). The Buhlmann/Workman idea is based on diffusion into a number of tissue groups (12 or 16 typically with less used in some computers [Suunto] or tables [PADI RDP]).
The 88s use a three group model and use a sort of perfusion/diffusion algorithm (if I understood Dr Hennesey's mail correctly).
The BSAC tables therefore are different to other models and cannot be 'compared' to models that use a different sort of thinking and modelling.
Neither are "right" or "wrong". However, much more work has been done recently by the likes of Bruce Weinke on the Buhlmann work than has been done on the 88s.
Nearly all of us use a Buhlmann model more or less or a derivative thereof (including the Suunto). You are slightly wrong therefore Philip as far as I can see, although understandably so - or totally correct if you want to be very pedantic.
Chris.

David Humm

23-10-2003, 18:02

Hi all

The link included in this post directs you to a scanned image of the current SAA Buhlmann tables.

Please feel free to save it if you so desire.

I'm sure many of you will have seen these tables before.

As a former member of BSAC I know the '88 tables, in comparrison, I find that the Buhlmann tables are more conservative throught most of the depths

They are compatable with most PDC. Can be used with EANx under the EAD principle. Ascent rate is 10mtrs per min with safety stop at 3mtrs

Hope this contributes.

Dave Humm
Viking Divers
Sub Aqua Association

<a href="http://www.divingisfun.com/images/tables.jpg" >http://www.divingisfun.com/images/tables.jpg</a>

Philip Smith

24-10-2003, 22:14

Nearly all of us use a Buhlmann model more or less or a derivative thereof (including the Suunto). You are slightly wrong therefore Philip as far as I can see, although understandably so - or totally correct if you want to be very pedantic.

I did say it was a small point, but I hope you're not saying it is pedantic to distinguish between Buhlmann and other multi-compartment models. Suuntos use a multi-compartment model, but they do not use a Buhlmann algorithm and, I think, never have. Originally they used the USN tables, then derivatives of the USN model, now they use a version of RGBM (or an RGBM modification of Suunto's Haldanean model).

Philip Smith

Peter MacIver

20-11-2003, 18:33

David Walker

22-11-2003, 17:47

The most conservitive wins!

Mostly that is the 88' tables - so what?
Safety is the first priority.

Its alright being safe, but the tables are absolutely no use if you want to do more than a couple of dives in a day, or doing continuous days diving for say a week. You'd have so much deco on every dive it would just not be worth diving anymore. Even if you do follow what the tables say for multi-day diving, they don't take account of the buildup over several days, so are inaccurate for that anyway.

My opinion of them is that they are fine for beginners who won't go past 20m more than once per day, for those who only dive for a couple of days in a row at most, or for those who like doing deco...! Even for wreck dives on a flat bottom they would be fine for a day or two in a row, since you are sticking to a fairly close square profile so aren't losing huge amounts of time with conservatism which only serves to restrict your diving.

Just set you computer to its most conservative, and that should be enough for anyone.

David

matt

24-11-2003, 18:21

Keith,
I, as like a lot of "old Scrots" in our Branch, use the '88 tables as a reference.
However, on a dive brief, SEEDS for those who have forgotten the acromyn, I always empasise the new ('88 Tables), but also make sure that my buddies, whether novice or equivalent to my leadership, ensure that at the end of the dive, at the 6 metre safety stop (oh yes, I insist on that no matter what the profile is!) that we look at both our computers and reference them against the '88 tables.

The most conservitive wins!

Mostly that is the 88' tables - so what?

For a no-decompression dive the 88's will almost always be more conservative than a computer. The no stop limits are pretty well understood and all tables and computers pretty much aggree. The difference then comes down to Tables Vs Computers.

For a mandatory decompression dive it is a very different story. A 30m 30min U Profile can result in a modern computer requiring significantly more decompression time than 88s (like around 20 minutes more). This is not just the difference between a computer and tables it is a fundamental difference between 88s and modern computer algorithms.

So we pretty much know how long it takes for enough excess Nitrogen to get into the bloodstream to prevent a safe return to the surface. What is less well understood is the procedure and time it takes to get Nitrogen out of the bloodstream.

Safety is the first priority.

Absolutely. The risk of a bend inside no stop limits is very low. The risk rises steeply the further into decompression you venture. DAN's Project Dive Explore is about the most comprehensive study of recreational decompression practice ever undertaken. The early indications make it harder than ever to defend the use of 88s in decompression diving.

With the increased prevalence of decompression diving what do you think Peter, should we be concerned?

John Bantin

29-11-2003, 12:45

The BSAC 88 tables are undoubtedly easy to use - and that makes teaching the use of tables easy too, for both instructor and trainee.

However, the question remains, In the light of current thinking are the numbers right?

I started using diving computers long before 88. Diving with those using tables (the majority in those days) I quickly discovered that there was a general inability on the part of most divers to monitor time and depth accurately with a watch and mechanical depth-gauge. I often did with others a ?30m dive for 20 minutes? only to need to do a computer stop because my electronic iinstrument had actually registered a dive to, say, 33m for 23mins.

So I believe that 1) the BSAC 88 tables are a good tool for teaching the concept of decompression schedules but 2) all divers should be encouraged to use a computer as soon as possible for the practical reason I mention.

As for ascent rates - only a computer can monitor that accurately.

Which computer and which algorithm? Well that is another can of worms!

So I say keep the 88 tables. Do not spend any more money on what is not really needed - but use pressure sensors and computer algorithms to monitor any actual dives. For mixed gas dives, plan with Proplanner or Abyss etc but use a compatible computer in the water.

Thats my opinion for what its worth!