DECO StOPs

[patmandu]

GDI,

If I came across as accusatory or anything of the like, my apologies. I'm here to learn and try to share what I've been taught. That being said.

I think any discussion on decompression between divers is a wonderful thing, and should be looked upon as an educational opportunity as well.

I don't doubt that your deco works for you and it's what you believe is right for you. My reservations are that: Maybe someone will read your post and decide that your deco approach is the right for them too, and go out and get hurt (I know they shouldn't do that from reading stuff on the internet, but there are alot of people out there...). Anyways, my second reservation is that decompression theory is an evolving one, and even if something works well for you, maybe it's not 'best' for you, if that makes sense.

I'm more than willing to discuss deep stops (with my limited knowledge) and why I think they make/do not make sense. I try to look at decompression with a common sense approach.....i.e. deep stops and slow ascents seem to make sense if you want to limit cascading of bubbles coming out of solution.

As for your student, have they read the bubble mechanic stuff that erik baker has written?

Here's a few links that may help to at least describe/introduce the notions:

ftp://ftp.decompression.org/pub/Baker/Deep Stops.pdf

http://www.decompression.org/maiken/VPM/Bubble_Model_Program_Info.htm

http://www.decompression.org/maiken/Bubble_Decompression_Strategies.htm

 

[GDI]

:doctor:
Patmandu and the rest of you I am sorry if my words are coming accross as harsh, that is not my intent. Deco diving is a very wide based subject with so many avenues to look at. By no means should this board be the sole source of information. patmandu I too continue to learn so much more about deco each and every time I look at it. I have seen alot of changes in the various techniques since my first work with bubble studies at DCIEM (now DRDC) We have not even touched the surface. The navy tables have been a base for many years for many divers BUT the navy also has a large man pool to complete their task and they also have the chambers on site or close by. I see the differences in V-planner, Z-Planner, Voyager, GUE and a few others out there. Some are similar more so than others and I suspect that the program designers each have influenced the parameters of their respective software.
However this thread like so many has given me the method to which I will be able to answer my students question. I enjoy students like this. If we do look back at my original question it had nothing to do with using tables/software but rather technique and reason. The Question(s) again is WHY do we do deep stops and why are they a good thing to do and how do we know when to do them or not to do them? Note that in theory I could go into decompression in only 33 ft if I had the gas. I can do the same at 130 ft and so on. All of this can be done by diving by tables. The purpose of deco diving is to "under control" reduce the gases pressure gradiant on the various tissue groupings of the body and to release these gases through the bodies own physiological means - diffusion out through the skin and respiratory system for example. IMO we do deep stops to allow the body to have a pressure gas tension release resting phase during the ascent reacclimating the body back to acceptable surface tension tolerances. These tolerances of course are particular to the individual and can vary from day to day. Dive tables at any level cannot factor the individual diver let alone on a day to day basis. They are designed to accomondate the average population characteristics of divers. Case in point the US Navy tables are suited for young very fit divers and a man pool of resources and really shouldn't be used for the average civilian diver. Now Why do you do or not do deep stops?

 

[IndigoBlue]

patmandu once bubbled...

Coming up slowly and gradually (i.e. rolling stops) starting at 80% of the max depth allows you to slowly off-gas and 'stop' (for lack of a better word) the rapid release of bubbles that you get if you just simply go up to the first required stop and then have to wait..... If that makes any sense.

Why do you believe it is 80%?

Is this an empirical finding? By whom?

 

[GDI]

:doctor:
Welcome Indigoblue and thank you for asking "WHY"
and what is your opinion on deep stops?

 

[IndigoBlue]

GDI once bubbled...
:doctor:
Welcome Indigoblue and thank you for asking "WHY"
and what is your opinion on deep stops?

I am still getting caught up on all the major posts on this site over the past 3 years. These contain some very interesting information.

I do not really have a personal opinion of deep stops. From the sound of the previous posts here, that subject is in flux. So I want to know what particular study helps Patmandu to settle upon 80%.

I have heard 50%, which Pyle made famous for deep air and collecting fish. I have also read that nitrogen and helium act differently, so it seems difficult to postulate one rule for all gas mixes, offhand. That is also why I ask.

I am curious to read Patmandu's sources.

 

[patmandu]

IndigoBlue once bubbled...


Why do you believe it is 80%?

Is this an empirical finding? By whom?

Good question, and I'm not sure I have a good answer for you. 80% certainly isn't a hard and fast rule for deep stops, and no I don't have any 'hard copy' studies of findings that 80% is THE place to start deep stops. Pyle stops at 50% may be the answer....I don't know.

What I like to do is start 'rolling stops' (30 seconds at the depth, 30 seconds to next 10 ft increment) until I reach 10 ft below my first gas switch at which I'll spend 60 seconds to get squared away, and ready for my gas switch (of course, if the schedule I'm running requires a longer stop, I'll do that). After the minute at 10ft below my gas switch, I'll spend 3-5 minutes minimum at the gas switch (starting once I am breathing the new gas).

I'm am by no means a deco expert and I don't recommend anyone follow what I do. I look at decompression from a perspective of what makes sense to me and what seem logical. Starting a controlled slow ascent from a deeper depth (say 80% for instance) allows me to slowly increase the gradient and slowly start to off-gas.

Where did I learn this? Mainly from trying to listen and learn from folks who I respect and routinely pull insane runtimes. I listen, try to understand their reasonings, and then pass it through my common sense/logical BullSh*t meter.

I use various decompression programs, analyze where the theoritical compartment off gassing starts to occur in the compartments and then 're-shape' the curve to build in sensical deeper stops.

Does that help to answer the question?

I welcome comments/debate/ etc. This is how we are learn

 

[GDI]

:doctor:
So patmandu you opt to do deep stops when required and of course taking the time to enter into your gas switch depth. If I understand you, you also do running time ascents, slow ascents stopping only when the profile calls for it, other than when adjusting yourself to switch gases? OK can see that

 

[patmandu]

GDI once bubbled...
:doctor:
So patmandu you opt to do deep stops when required and of course taking the time to enter into your gas switch depth. If I understand you, you also do running time ascents, slow ascents stopping only when the profile calls for it, other than when adjusting yourself to switch gases? OK can see that

I would agree with that statement. The only caveat is that I tend to 're-shape' the output from the computer profile to include more time at deeper and intermediate stops and a reduction in the shallower stuff, to 'round out' or 'reshape' the deco profile. Although some of the VPM profiles are very close to what I would 'like' to see.

 

[pipedope]

Comes from GI3 at the WKPP.
Go to the WKPP web site and read the articles on DECO;
http://www.wkpp.org/decompression.htm

 

[patmandu]

pipedope once bubbled...
Comes from GI3 at the WKPP.
Go to the WKPP web site and read the articles on DECO;
http://www.wkpp.org/decompression.htm

Well, there you go. Thans for the link. If it's not obvious, I'm GUE trained and one of my instructors is a WKPP diver with whom I've had alot of diving related discussions.