Decompression Algorithms

[julian.carroll]

What decompression algorithm do you use for planning your dives?

[bythesea]

Suunto is not an algorithm...

[Michael Purcell]

Suunto is not an algorithm...

Fair enough but what name would you use for it?
It isn't a pure RGMB, and saying Suunto certainly defines the algorithm they are asking about...

[Nigel Hewitt]

Hey where's the 'nothing' option?

My dive planning consists of a slip of laminated paper with the max run times against depths that my bailout will get me out on. I might use it but I probably won't.

There is no plan when I get in the water. Plans are for OC divers and even my bit of paper only becomes relevant if the RB blows up and I have to resort to my nasty OC bailout (once in nine years so far). OC needs a plan because it needs a gas plan.

Yes I am talking about 70 meter dives with well over an hour of deco. That's why I have two computers from different manufacturers.

[Woz]

Teaching: 88s
Diving: VR3 (Buhlmann + Pyle stops)
Back check: Ratio deco

[Gordon]

I've got a VR3 and a Suunto.
If I'm doing anything fancy the Suunto is in gauge mode.

[garethwoodruff]

V-Planner as back up with Suunto Vyper in guague mode.

Suunto HelO2 for running the dive and using with the new sunnto dive planning software.

I'm coming out of deep dives feeling really good so it appears to work for me.

[Hickdive]

Suunto Helo2 on -2 conservatism with tables cut on Baltic VPM-B on +5 as back up. Those seems to give roughly the same sort of results in terms of TTS.

Like Gareth I come out of deep (for me, that's 65m on trimix, which is probably pretty shallow for many others) dives fairly bouncing with health and vitality.

Therefore it seems to work for me.

[Richard Whitcombe]

Teaching BSAC im forced to teach 88s. Don't and would never actually use them for dives though.

Decompression diving usually VPM.

"Work" diving, whatever the Suunto on my wrist tells me backed up with some common sense.

[julian.carroll]

How come nobody uses RGBM?

I'm just getting into deep (40m) decompression diving so that's why I posted the poll. Looking online (and by the results of this poll), Buhlmann seems to be the algorithm that is thought of most highly.

However, on a recent weekend I was very surprised that two dives to 38m for 20mins with just a 3 hour surface interval between them produced identical profiles. I would have thought the nitrogen loading from the first dive would have penalised me heavily for the second dive. Interestingly, the BSAC 88 tables gave about 3mins of stops for the first dive, but wouldn't even allow the second dive!

[Woz]

No-one uses RGBM cos taking a Cray down with you is tricky. Buhlmann is so popular cos it's licence free.

[Nigel Hewitt]

How come nobody uses RGBM?

I'm just getting into deep (40m) decompression diving so that's why I posted the poll. Looking online (and by the results of this poll), Buhlmann seems to be the algorithm that is thought of most highly.
Bühlmann is the one that has done the hours.
Be it right or wrong the rule seems to be that if your exciting new XYZ deco theory and computer model gives less stops the Bühlmann you get bent and people notice that. Since we hobby divers aren't quite up to the fitness levels of Prof. B's guinea pigs we like to pad some extra on it but it's actually very difficult to prove that extra stops actually mean safer.

[TrevorB]

I always use BSAC Nitrox tables where everpossible for teaching and recommend thats the ones the students buy

SD requires 88 for altitiude, training, but Nitrox are more use and a better buy

[Mike Halligan]

I always use BSAC Nitrox tables where everpossible for teaching and recommend thats the ones the students buy

SD requires 88 for altitiude, training, but Nitrox are more use and a better buy

This depends on accessibility of Nitrox at the club's routine dive sites. I and others found the cost of O2 cleaning etc wasn't justified by the very rare availability of Nitrox where we dive.

So, we provide copies of BSAC Nitrox tables for student use, having first required that they all buy BSAC 88s. In the unlikely event that they decide to dive Nitrox, they are able to buy Nitrox tables at the discounted (bulk) price through the branch.

[TrevorB]

Thanks Mike

Same problem
we have an O2 cleaned pony for OT4 and simulated Nitrox diving in training where they measure the pony do the CNS MOD calcs but dive on air

Often on away trips Nitrox is available at very reasonable costs ie it was free in Tenerife so everyone got train using it for real

Never dive at altitude is just and SD paper exercise, so they borrow 88 tables in the lectures and test, but if buying I always say buy Nitrox

[bythesea]

Never dive at altitude

Unless it is a skydive... I always try to dive below sea level as a rule.....

[MattDuke]

Since we hobby divers aren't quite up to the fitness levels of Prof. B's guinea pigs we like to pad some extra on it but it's actually very difficult to prove that extra stops actually mean safer.

I think it's pretty easy to show that missed stops mean more dangerous, and thus I don't want to do the "Minimum decompression" I can, unless another factor forces me too.

My take on Deco Algorith is the following:

- Vplanner +3 makes me feel very good after 60-70m diving, Open Cicruit, Oxygen as final deco gas

- Vplanner has lesss stops at 6m than I am always comfortable with, so I "Pad" the final stop as my own personal "J" factor. I have a strong belief that spending extra time at 5m and a VERY slow ascent to the surface are a smart thing to do.

In this way I have chosen an Algorithm that feels good (No tiredness after dives) but I haven't just abandoned all the impherical evidence from people like comex who strongly reccomend extended stops shallow.

This works for me.

[Woz]

Thanks Mike

Same problem
we have an O2 cleaned pony for OT4 and simulated Nitrox diving in training where they measure the pony do the CNS MOD calcs but dive on air

Often on away trips Nitrox is available at very reasonable costs ie it was free in Tenerife so everyone got train using it for real

Never dive at altitude is just and SD paper exercise, so they borrow 88 tables in the lectures and test, but if buying I always say buy NitroxStoney Cove on a grim day is high enough that you need to go to Level 2.

[TrevorB]

Thanks Woz

We use Capernwray and some days it could be argued its a level 2 dive

Being a Uni club students are never going to own both sets of tables

I think I adopted the advice "buy Nitrox tables from BSAC" although I might have trouble finding it documented

I dislike using copies of tables as somone earlier in the thread mentioned, not only because of copyright, but someone might actualy dive on them

There used to be extracts from 88 tables in the manuals so students could home study with the interactive web, but they seem to have gone in the new manual, and all my old manuals are long gone, when you loan thing you never get 100% returns

So now I own 8 Nitrox and 5 88 tables and they come out in class and go back in my case, not an ideal situation, but some of the keen students do buy their own and it does warm your heart when you see this level of motivation

[Jen - Winged Blob]

Are you on about that upper car park again, Woz? :D

[PeteM]

Are you on about that upper car park again, Woz? :D

Stoney lake is 77m above sea level, if the barometric pressure is below about 995mB then you should be on Level 2 tables - and it is only 20mB above that at the moment ;)

[Gordon]

Trevor,

We get all of our Ocean Diver trainees to buy a set of air 88s, and all our sports trainees to buy a set of Nx 88s. That way, the ODs don't get confused about what tables they can use and the sporties have everything they need to pass the exams. It's probably a bit unnecessary, given the number of dives anyone has done on the 88s - but it means that everyone is self sufficient and the branch doesn't have to worry about having enough copies of tables to go around.
That, and once the students have spent some money, they tend to hang around.

YMMV,


G

[Nigel Hewitt]

I think it's pretty easy to show that missed stops mean more dangerous, and thus I don't want to do the "Minimum decompression" I can, unless another factor forces me too.
No argument with that but the whole problem with conservatism is that we have lots of good ideas (GF is a great idea and I like it) but no real way of even defining the problem.

The whole question resolves to 'how far from the edge of the cliff' is safe?

I'm currently reprogramming a dive computer and so this is a very important but rather perplexing question to me just now. If I could come up with a formula for 'twice as save' life would be so much easier.

[TrevorB]

Thanks Gordon

Must be more money where you are, I don't think I could acheive that

I think at OD then the tables are very simular except no Altitude table for the Nitrox users, and no examples which are useful

I take Woz's point on barametric pressure, but at OD they will know how to use the altitude table and get to level 2, but is the transfer table only in Sports Diver studies so they wont know how to get to 2B

Dangerious my notes are not to hand am I going to get shot down

[Jen - Winged Blob]

PeteM Quote:
Stoney lake is 77m above sea level, if the barometric pressure is below about 995mB then you should be on Level 2 tables - and it is only 20mB above that at the moment


Yup - I realised there was a factual side to it - but it's just that Woz (quite justifiably!) has expressed views about that upper car park... ;)

[Woz]

PeteM Quote:
Stoney lake is 77m above sea level, if the barometric pressure is below about 995mB then you should be on Level 2 tables - and it is only 20mB above that at the moment


Yup - I realised there was a factual side to it - but it's just that Woz (quite justifiably!) has expressed views about that upper car park... ;)Only in a "waking up in the middle of the night screaming" sort of way :)

[Gordon]

Thanks Gordon

Must be more money where you are, I don't think I could acheive that

I think at OD then the tables are very simular except no Altitude table for the Nitrox users, and no examples which are useful

I take Woz's point on barametric pressure, but at OD they will know how to use the altitude table and get to level 2, but is the transfer table only in Sports Diver studies so they wont know how to get to 2B

Dangerious my notes are not to hand am I going to get shot down

We just tell them - you need these, they cost this much, and they all nod along and hand over their student loans to the diving club :) That, and £15 isn't really extorsionate.
We've had a few guys run into trouble trying to use Nx tables in OD exams, so we just don't give them the option to get it wrong! Also, if they choose to go diving outside of the branch (on holiday, for example) they have their own set of tables to use.

[PeteM]

We just tell them - you need these, they cost this much, and they all nod along and hand over their student loans to the diving club :) That, and £15 isn't really extorsionate.
We've had a few guys run into trouble trying to use Nx tables in OD exams, so we just don't give them the option to get it wrong! Also, if they choose to go diving outside of the branch (on holiday, for example) they have their own set of tables to use.

My old club used to quote prospective new members a price for "books" that were required for training, the books besides the manual and QRB included the 88's

[Ron MacRae]

Stoney lake is 77m above sea level, if the barometric pressure is below about 995mB then you should be on Level 2 tables - and it is only 20mB above that at the moment ;)

According to my map Stoney cove is at 88m with a lot of the shoreline being over 100m.

Again according to my map, Vobster Quay is at 138m. Looking at the Altitude /Atmospheric Pressure Chart anything less than 1000mB is on level 2.

I've no idea if my map is better than yours :p, but it's supposedly based on Ordenancee Survey data:confused: .

Ron.

[PeteM]

According to my map Stoney cove is at 88m with a lot of the shoreline being over 100m.

I think you are probably right, when I wrote that post I was going to type 88m from memory but thought I had better check it. The source I found did not look 100% reliable but I did not have time to look further.

[Woz]

I've been at Stoney, checked my VR3's display and it's definitely been a level 2 dive when it was hosing down.