Nitrox and Suunto Vyper computer

[TexasMike]

Which was (paraphrased) how to perform the dive when you are watcing the NDL numbers on your computer.

To restate, if you descend to a particular depth and stay there (+/- a few feet), you will see your computer wind down from the max NDL time it has computed towards zero.

Piscean's point was to follow a conservative profile by NOT waiting until it reaches zero to ascend. Piscean suggested to begin moving shallower once your NDL clock drops below 10% of the remaining time for that depth.

When diving nitrox, the same concept can apply. Your time at the depth is still governed by the NDL clock, so moving upwards before it hits zero is smart diving.

 

[Piscean]

Sorry DivingDoc - I didn't know you were an MD - in fact I wish I had known, would have saved me lots of typing. Anyway, Texas Mike seems to have distilled my reply very nicely.

Piscean.

 

[Zept]

Originally posted by DivingDoc
I'd like to know how you personally use the computer for your multilevel dives.

I plan my multilevel dives using the Wheel. During the dive I use the computer to monitor depth and time, to make sure I'm sticking to my plan. I keep an eye on the no-decompression time, just in case, but it's the predetermined plan that governs the dive. I do it this way for several reasons:

-- Some of the people I dive with don't have computers
-- Computers aren't infallible, so it's good to have a backup
-- (OTOH my brain isn't infallible, so it's good to have the computer)
-- It's easier to agree on a plan before we hit the water

Probably not the answer you wanted, but it works for me! It isn't as much hassle as it sounds, because we have a few basic plans that we use frequently.

If you do the multilevel dive during your AOW, you might be introduced to the Wheel. I found it headbending at first, but now I like it.

Hope your courses go well,


Zept

 

[Dr Deco]

Dear Readers:

In all of these discussions concerning gas loading, please remember that this is only a part of the equation. The other part is tissue micronuclei (seeds) that grow during decompression. Without the nuclei, there would be no free gas phase. Conversely, without supersaturation, there would be no nuclei growth.

While it is of great value to limit the supersaturation of the dissolved nitrogen, especially during the ascent phase of the dive, it is also important to not form nuclei. This could occur as one climbs into the boat wearing all of their heavy gear. I have also heard of individuals playing beach volleyball and other very strenuous activities during the surface intervals.:boom:

Dr Deco
:doctor:

 

[DivingDoc]

Originally posted by Dr Deco
Dear Readers:

While it is of great value to limit the supersaturation of the dissolved nitrogen, especially during the ascent phase of the dive, it is also important to not form nuclei. This could occur as one climbs into the boat wearing all of their heavy gear. I have also heard of individuals playing beach volleyball and other very strenuous activities during the surface intervals.:boom:

Dr Deco
:doctor:

Are micronuclei the same is microbubbles? What else to do need to avoid in order to keep from forming them?

What I have been trying to figure out is 1) when you are using a nitrox computer, how important is it to bw able to continue to monitor your pO2 and where it is at the moment (even if it is below your planned max -- usually 1.4) as the same time as you are monitoring your nitrogen loading.

I'm asking because computers such as the Atmos2 and the Oceanic Versa Pro allow you to monitor both at once, whereas the Suuntos show only the OLF graph when set for Nitrox and the N loading graph when set for air. You can never see both at once. The Suuntos also will only display your pO2 when they alarm because you've reached a pO2 of 1.4.

Elaine

 

[The Iceni]

Hi Elaine,

Here I am again!

I find this thread particularly interesting as it illustartes at least three styles of diving.

1) Planned no-stop dives, with computer assisted ascent for stops only if they become necessary.

2) Planned decompression dives using a PC, Palm, Tables or The Wheel, to generate a run sheet to use on the dive with a timer, the computer is for back-up only. The majority of UK teckies dive this way, and

3) Deco dives relying on the computer alone.

The majority of my diving is on wrecks in the North Sea (or the Altantic) so it is largely sqare profile. Thus I plan for any necessary decompresion requirements before the dive - style 2. "Plan the dive and dive the plan."

If multi- level diving is what I think it is - on reefs and walls at varying depths- this style of diving cannot be accurately planned so easily. If I am right at your level this will be style 1. If so, do you really need all that information you have described during the dive? Surely all you need to do during a properly planned dive is

1) to keep a weather eye on your depth so you do not exceed the planned maximum depth and especially the MOD (for oxtox).

2) to keep the other eye firmly on your run time so you do not exceed the no stop limit, or your planned bottom time.

I might find an audible alarm at 1 minute before the no- stop limit - or planned bottom time might be a uselful feature on a computer. I would find the bar graphs you describe of not much practical use, and they increase task loading to boot. If you are confused on the surface, think how confusing it would be when you are suffering the effects of narcosis.

Dive style 3

I suspect multilevel technical dives will require meticulous planning to avoid unecessary deco. I also suspect few deep cave divers will rely on even the most advanced decompression computer although a few are now being produced to allow just that (ie on board pre-dive switchable algorithms and multiple in-flight gas or set-point changes), these computers do not remove the need for adequate gas planning, however.

Have these computers caught on in the US and is style 3 practiced over there by mulitilevel cave divers, for instance?

It has not really caught on in the UK.

 

[DivingDoc]

Originally posted by Dr Paul Thomas
Hi Elaine,

Here I am again!

I find this thread particularly interesting as it illustartes at least three styles of diving.

1) Planned no-stop dives, with computer assisted ascent for stops only if they become necessary.

2) Planned decompression dives using a PC, Palm, Tables or The Wheel, to generate a run sheet to use on the dive with a timer, the computer is for back-up only. The majority of UK teckies dive this way, and

If multi- level diving is what I think it is - on reefs and walls at varying depths- this style of diving cannot be accurately planned so easily. If I am right at your level this will be style 1. If so, do you really need all that information you have described during the dive?

OK -- here's what I mean. We are going to be doing nice warm tropical diving in Cozumel. In multilevel diving, you start deep -- up to 130 fsw, but only stay there briefly -- you then gradually move up, decreasing your depth in a stepped fashion, going over gradually rising terrain, all the time keeping within no-deco limits. You need a computer for this because if you just use dive tables, you would have to count your deepest depth as the depth for the whole dive. The computer can give you extra no-deco time based on your gradually decreasing depth.

Also on the same trip we will be going both our Advanced OW and our nitrox certification. So I will need a computer that is able to keep me out of Ox-Tox.

 

[Piscean]

Elaine,

The OLF which the Suunto shows is not the same as the partial pressure of oxygen. The Suunto shows the partial pressure of O2 where the air time would be until you have less than 30mins of air time left, then it shows the air time remaining in that position (that is the large size numbers on the left of the display).

The OLF bar graph is a representation of the percentage of the allowable cumulative central nervous system oxygen exposure used up. It is important to know about that. If you use all of that up you are prone to spontaneous convulsions even below 1.4 ppO2.

You do not really need to know the current ppO2 IMHO. Normally when I plan a nitrox dive I decide on a max ppO2 before I go into the water and that is translated into a maximum operating depth (MOD). This max depth is how I monitor my ppO2. If my actual depth is less than my MOD, then my ppO2 is less than my max ppO2 and that is all I worry about. If I calculate my oxygen exposure on tables then I assume as for nitrogen loading, that I am at the max depth (which may not be the same as the MOD) for the whole dive.

Dr. Paul, please read through my long post earlier and see if you don't agree, that the real advantage of the bar graphs is that they show you your current percentage of you total allowable exposure (either to O2 or N2) corrected for that particular depth. That corrected for depth thing is important because if I ascend with 2 minutes of no-stop time left from 130 feet that was quite conservative as I have only used 80% of the no stop time. If I ascend with 2 mins left from 35 feet then I have used 99% of the no stop time so it is not so conservative. If I always ascend with 9 out of 10 blocks on the bar graph lit up then I always only use 90% of my no-stop time. I think that is the real advantage of the bar graph.

Piscean.

 

[Dr Deco]

Dear DivingDoc:

The aspect of micronuclei is, I believe, important in diving and decompression. The micronuclei are what some people call “microbubbles.” They are the seeds that can grow as decompression bubbles to the point where pathology occurs. There are several points to bear in mind concerning micronuclei.

1. The ability for water to form bubbles by supersaturation alone is almost nil.

2. For the small pressure changes that are encountered by divers, it is necessary that the micronuclei be present in the liquid.

3. Nuclei are formed by heat (as in boiling), and by kinetic activity of the fluid when small, low-pressure volumes occur (hydrodynamic cavitation).

4. The nuclei are stabilized for a few hours by the adsorption of surfactants.

5. The nuclei can grow when the supersaturation pressure exceeds the Laplace pressure (= shrinkage pressure that results from a non-zero surface tension).

6. Slow ascents allow for the loss of dissolved nitrogen into the blood capillaries. It also prevents the nuclei from enlarging in accordance with Boyle’s law (and thus expanding the bubble radius and reducing the Laplace pressure).

7. Musculoskeletal activity also favors hydrodynamic cavitation and nuclei generation. These activities during the surface interval and immediately following the last dive of the day include climbing boat ladders, carrying heavy gear, swimming, playing volleyball, and so forth.

Dr Deco
:doctor:

 

[DivingDoc]

Originally posted by Piscean
Elaine,

The OLF which the Suunto shows is not the same as the partial pressure of oxygen. The Suunto shows the partial pressure of O2 where the air time would be until you have less than 30mins of air time left, then it shows the air time remaining in that position (that is the large size numbers on the left of the display).

You are talking about Suunto's air-integrated computers, right?

The OLF bar graph is a representation of the percentage of the allowable cumulative central nervous system oxygen exposure used up. It is important to know about that. If you use all of that up you are prone to spontaneous convulsions even below 1.4 ppO2.

So in Ntrox diving -- you only need to look at the OLF bar graph -- Nitrogen loading isn't important?? I'm asking because the Pelagic computers (Atmos and Oceanic) dispay both the Nitrogen saturation graph and the O2 graph at the same time along with an ascent rate bar graph, which appeals more to me than the single bar graph that Suunto displays. OTOH, I hear Suuntos break down less often and have longer battery life and nice download graphs. Also -- I would like to see where I'm at in terms of moving up to Oxtox before I get an alarm that tells me that I've reached it!

You do not really need to know the current ppO2 IMHO. Normally when I plan a nitrox dive I decide on a max ppO2 before I go into the water and that is translated into a maximum operating depth (MOD). This max depth is how I monitor my ppO2. If my actual depth is less than my MOD, then my ppO2 is less than my max ppO2 and that is all I worry about. If I calculate my oxygen exposure on tables then I assume as for nitrogen loading, that I am at the max depth (which may not be the same as the MOD) for the whole dive..[/B]

But O2 "loading" is not just depth dependant, as I understand it. It is both depth and time dependant. Therefore you cannot simply use your depth as a measure of your estimated O2 toxicity risk.

I'm trying to understand so I can choose the right computer for me.

ET