PSAI Narcosis Management course - 73m on air

[Kern]

As I already said, I used deco planner - I just don't have it here at the moment

.... and the answer to the 2nd paragraph is......

 

[Tortuga68]

The deco schedule was finished. Of course you keep off-gassing during your surface interval, I don't consider that part of the deco schedule though

Instead of trying to pick holes in what I say, why don't you share your own viewpoints where they differ from the ones I express - that would be a little more constructive, don't you think? It's gets a little tiring when people just 'demand' answers to their questions, especially when many of them have either already been covered or are irrelevant

 

[Kern]

The deco schedule was finished. Of course you keep off-gassing during your surface interval, I don't consider that part of the deco schedule though

Instead of trying to pick holes in what I say, why don't you share your own viewpoints where they differ from the ones I express - that would be a little more constructive, don't you think? It's gets a little tiring when people just 'demand' answers to their questions, especially when many of them have either already been covered or are irrelevant

I'm not talking about the surface interval & I think you know it. Do you really think it makes sense to stop using a low to 0% N₂ mix/gas & move to a high % N₂ mix while still under water & then breath it for several minutes? Even though the aim of the exercise is to clean out as much N₂ as posable. There are rules to the use of all tables. What you suggest is not the way any table I'v encountered is designed to be used.

I'm not trying to pick holes in what you say at this point. I'm asking you questions because I can't believe you've said most of the things you have in this thread. I also think it would be a disservice to newer divers who might read this thread to leave it unchallenged.

So asking questions on a discussion board is now demanding answers. Why do so many people on these boards want to start a thread but not have a discussion? HUPP.

 

[Tortuga68]

Another poster mentioned the surface interval as part of off-gassing, that's why I commented on it. Sorry, I thought you might have read the thread

Asking questions is not demanding answers, but asking questions then making follow-up posts saying '.... and the answer to the 2nd paragraph is......' certainly seems like it

I'm all up for having a discussion, I just don't see a lot of discussion happening in this thread (with some notabe and appreciated exceptions). I'd already made it clear I was using decoplanner, and that I don't have my gear with me, so those questions had already been answered. To be honest once I read the first couple of questions you re-asked, I kinda lost interest in your post

Anyway, thanks for sharing your thoughts on deco gas switches, the newer divers can now rest in peace, figuratively speaking - although your point had already been made by Mike. Also I would have thought people doing deco dives would have received sufficient training to make their own minds up on gas switching, rather than reading something on the internet and copying it; especially in a 73m deep air thread

You are correct that switching from 100% to air for the 3 minute ascent from 4.5m to the surface will add nitrogen loading compared to ascending on O2, however N2 isn't the only issue with diving, and the purpose of deco is not to eliminate all N2 buildup

If you'd like to discuss it further, be my guest, although it is unrelated to the thread topic

 

[CDNScubaMoose]

Thanks for sharing your experience with this course. I had heard of this course before and although I had never considered it for myself ... your experience's have been a useful insight for myself.

However I do have a few questions/thoughts?

You are correct that switching from 100% to air for the 3 minute ascent from 4.5m to the surface will add nitrogen loading compared to ascending on O2, however N2 isn't the only issue with diving, and the purpose of deco is not to eliminate all N2 buildup

The above statement has me scratching my head - I have some limited experience with deco diving so please bear with me, but isn't the purpose of deco stops to reduce your N2 load to a point where you can ascend without have the gas come out of solution? So by my reasoning (and that of others) by switching to your backgas (air) you would be then adding more N2 back into your system, thereby increasing your risk of DCS. I am cusious if in your plan you had planned for this extra N2 being reabsorbed and had a more conservative deco schedule in place to allow this (you didn't mention you took a DCS hit, so I assume the gas switch was of a non-issue)? Also what are the other issue(s) that you refer to that I assume you were trying to mitigate by making that gas switch?

I am also curious as to the reason you took this course ... you have mentioned many times that it was to help you learn to manage narcosis. I would like to know why you want to manage narcosis in this manner? I'm not trimix certified but I understand that He is probably the best way to manage narcosis ... so this course seems redundant to me. However I am sure there must be a logical reason for your choice. Are you planning a trip or dive in an area where He is not overly available? Are you taking your time to become trimix certified but want more experience in deco so you are planning on doing more deco dives and thus want to try to better prepare yourself for narcosis on these dives? I think you alluded to the idea that you want to take an extended range course in the near future - why not go the trimix route instead?

 

[coldsmoke]

I have never once asked how to calculate MOD in this thread - but don't let the facts get in the way of your little jibes from the sidelines

3. The PO2 issue. It is widely recognised that the acceptable limits for Po2 are 1.4 MAX and 1.6 as a CONTINGENCY!

BTW what's the recommended MOD of 18/45?

Hunter

 

[Tortuga68]

Great quotes coldsmoke, I read them already. Do you have a point you wish to express?

 

[Tortuga68]

1. isn't the purpose of deco stops to reduce your N2 load to a point where you can ascend without have the gas come out of solution?

2. So by my reasoning (and that of others) by switching to your backgas (air) you would be then adding more N2 back into your system, thereby increasing your risk of DCS.

3. I am cusious if in your plan you had planned for this extra N2 being reabsorbed and had a more conservative deco schedule in place to allow this

4. (you didn't mention you took a DCS hit, so I assume the gas switch was of a non-issue)?

5. Also what are the other issue(s) that you refer to that I assume you were trying to mitigate by making that gas switch?

6. Are you planning a trip or dive in an area where He is not overly available?

7. Are you taking your time to become trimix certified but want more experience in deco so you are planning on doing more deco dives and thus want to try to better prepare yourself for narcosis on these dives?

8. why not go the trimix route instead?

1. Yes of course, I did that

2. Potentially, but not beyond what I consider acceptable levels

3. It was accounted for

4. As someone mentioned earlier, decompression is not an exact science. You can follow all the 'rules' and still get a DCS hit and vice versa. So, not getting a DCS hit doesn't mean what you did was 'right' (including what I did, in some people's opinions). However no I did not get one

5. Any gas you breathe under pressure can be dangerous, including O2. The PPO2 of O2 is of course much higher than that of air (21%), for example. So it's not all about reducing your N2. That's not to say what I did was right or wrong, but it's the way I was taught, it's worked for the people that taught me and it's worked for me, so far anyway. There are also practical issues with surfacing on a stage bottle that I mentioned earlier

6. Maybe, but that wasn't the reason. Nor was cost

7. I have no current plans to do a trimix course, as I have no plans to do working dives beyond the accepted limits of air; but yes I wanted more deco experience and if diving deco on air then of course being able to better cope with the symptoms of narcosis is desirable

8. I don't see the need currently, I found this more interesting. As I said I don't have any reason to do trimix diving at the moment ie there's nowhere that I am diving now that has sites that would make trimix beneficial IMO

BTW I don't advocate anyone doing these types of dives without proper training. I think you should do an adv nitrox/deco course to start with if you haven't already, then you can make your own mind up about what schedule and procedures you want to follow. As you've seen already there are plenty of people that disagree with what I've posted, that's fine

 

[Blackwood]

So by my reasoning (and that of others) by switching to your backgas (air) you would be then adding more N2 back into your system

My (non-expert) suspicion is that he wouldn't be adding more N₂. At 3m (from a 73m dive) I suspect he'll still have positive offgasing gradients. Rather, he'll be removing inert gases with less efficiency.

 

[UCFKnightDiver]

7. I have no current plans to do a trimix course, as I have no plans to do working dives beyond the accepted limits of air; but yes I wanted more deco experience and if diving deco on air then of course being able to better cope with the symptoms of narcosis is desirable

8. I don't see the need currently, I found this more interesting. As I said I don't have any reason to do trimix diving at the moment ie there's nowhere that I am diving now that has sites that would make trimix beneficial IMO

As I understand you said you have no plans to dive to the depths that you went to in your PSAI class if this is the case, what do you feel are the accepted limits of air? Or rather to what depths do you plan to dive outside of this class on air?