deep stops or not

[dreamdive]

I think one of the key issues with using "deep stops" in recreational limits is:

1. Understand that you are off gassing fast tissues but are loading medium and slow tissues
2. During slow ascents, you are doing the same!
3. Off-gassing fast tissues in recreational diving may not be an important issue! It is the medium and slow tissues that get you into trouble after your ascent and once you are on the surface.
4. Off-gassing fast tissues is an issue with long, deep dives - saturation diving.

Consider this: If you want to add to your conservatism, add additional minutes to your last stop depth rather than adding stops deep.

Claudia

 

[halocline]

3. Off-gassing fast tissues in recreational diving may not be an important issue! It is the medium and slow tissues that get you into trouble after your ascent and once you are on the surface.
4. Off-gassing fast tissues is an issue with long, deep dives - saturation diving.


Claudia

This doesn't make sense to me. My understanding is that in typical recreational conditions the fast compartments are 'usually' controlling. With lots of repetitive long dives the slower compartments become more of an issue.

Can you explain?

 

[dmainou]

You are right the controlling tissue is likely to be the fast tissue. However by performing deep stops you are simply unnecessarily loading the slower tissues.

The problem gets compounded on multiple dives on a single day or trip. Then you get a so called undeserved, but rightfully gained, hit.

Sent from my GT-I9300 using Tapatalk

 

[dreamdive]

You are right the controlling tissue is likely to be the fast tissue. However by performing deep stops you are simply unnecessarily loading the slower tissues.

The problem gets compounded on multiple dives on a single day or trip. Then you get a so called undeserved, but rightfully gained, hit.

Sent from my GT-I9300 using Tapatalk

+1

Halocline: That is why in the original post a diver had no deco at the end of his dive, but because he did a deep stop suddenly had deco. You are loading during your ascent! I can't show this here, but if you think that medium tissues are fast + slow divided by two, it is not! You have a lot more room before worrying about supersaturating your fast tissues! It takes a much longer time for the others to load but also a lot more time to unload!

Instead of adding a deep stop, add time at your 20 ft stop!

 

[halocline]

+1

Halocline: That is why in the original post a diver had no deco at the end of his dive, but because he did a deep stop suddenly had deco. You are loading during your ascent!

Instead of adding a deep stop, add time at your 20 ft stop!

Yes, I understand all of this, in fact I've posted basically the same thing earlier in this thread and in others like it. What I was questioning in your post was the statement about off-gassing fast compartments not being an issue in recreational diving. Typically the fast compartments are the controlling compartments in recreational dive profiles.

Anyhow, I now see that you were sort-of saying something similar, I just misunderstood your intent.

 

[Qasar]

I would like to thanks all valuable inputs made in this thread, as if it seems that the jury is still out about deep stops for rec dives...
I found an interesting paper about deep stops "Clearing up the confusion about deep stops" here.http://www1.maths.leeds.ac.uk/~read/scuba/baker2.pdf
If you take time to read and understand the graphics, you see that deep stops prevent to create a large and rapid overpressure gradient that is basically creating bubbles... But the example given is for a deep tec dive, I don't know if it's really relevant for a 30m no decco dive.

 

[dreamdive]

I would like to thanks all valuable inputs made in this thread, as if it seems that the jury is still out about deep stops for rec dives...
I found an interesting paper about deep stops "Clearing up the confusion about deep stops" here.http://www1.maths.leeds.ac.uk/~read/scuba/baker2.pdf
If you take time to read and understand the graphics, you see that deep stops prevent to create a large and rapid overpressure gradient that is basically creating bubbles... But the example given is for a deep tec dive, I don't know if it's really relevant for a 30m no decco dive.

This paper is not. And, there have not been any studies showing efficacy for deep stops in recreational diving! Again, if you want to add conservatism, add time to your last stop which should be your safety stop anyway. Add 3 minutes to that but unless you want to find yourself in deco, stay away from "deep stops".

 

[Ricky B]

Then you get a so called undeserved, but rightfully gained, hit.

I understand that calling some incidents of DCS an "undeserved hit" is simply a shorthand term to reflect that a diver complied with the tables or a dive computer but got DCS anyway, but I don't like the concept. It implies that DCS after noncompliance with the tables or a dive computer is "deserved." The tables simply predict (fairly well but not infallibly) whether someone will get DCS. Saying a hit is "deserved" or "undeserved" is a moral judgment that, for me, is out of place for someone stricken with an illness and that stigmatizes the diver. That in turn creates an environment which contributes to divers going into denial about having gotten DCS, which in turn delays treatment.

My way of thinking about an incident of DCS is that it was either probable or improbable. If there has been strict compliance with the tables or a dive computer and an incident of DCS occurs, it's an improbable incident of DCS. If a diver significantly exceeds the time given by the tables or a dive computer and an incident of DCS occurs, it's a probable incident of DCS. Use of the terms "probable" and "improbable" more accurately conveys to the beginning diver (and average diver too?) the uncertainty in decompression theory. For those reasons, I prefer not to refer to incidents of DCS being undeserved or deserved.

I am not criticizing anyone for using the "deserved" or "undeserved" terms. I am simply saying how I think of it, and what I think is a more helpful approach.

 

[gcarter]

I understand that calling some incidents of DCS an "undeserved hit" is simply a shorthand term to reflect that a diver complied with the tables or a dive computer but got DCS anyway, but I don't like the concept. It implies that DCS after noncompliance with the tables or a dive computer is "deserved." The tables simply predict (fairly well but not infallibly) whether someone will get DCS. Saying a hit is "deserved" or "undeserved" is a moral judgment that, for me, is out of place for someone stricken with an illness and that stigmatizes the diver. That in turn creates an environment which contributes to divers going into denial about having gotten DCS, which in turn delays treatment.

My way of thinking about an incident of DCS is that it was either probable or improbable. If there has been strict compliance with the tables or a dive computer and an incident of DCS occurs, it's an improbable incident of DCS. If a diver significantly exceeds the time given by the tables or a dive computer and an incident of DCS occurs, it's a probable incident of DCS. Use of the terms "probable" and "improbable" more accurately conveys to the beginning diver (and average diver too?) the uncertainty in decompression theory. For those reasons, I prefer not to refer to incidents of DCS being undeserved or deserved.

I am not criticizing anyone for using the "deserved" or "undeserved" terms. I am simply saying how I think of it, and what I think is a more helpful approach.

Political correctness, nothing more.

Deserved / underserved are not moral judgements any more than earned / unearned or probable / improbable are. The outcome is earned by the action, or unearned by compliance with protocol.

In addition, probable / improbable implies it may not have happened.

Sorry to sound harsh, but if someone delays or avoids treatment because of a label, then Darwin is at work. My health is more important that what someone else may think.

If I break a leg because I jumped off the garage roof, am I going to avoid medical help because someone might think I deserved (earned) my injury because I strayed outside the bounds of what is generally considered an unwise height from which to jump?

Silliness that unfortunately is gaining too much traction with repetition.

 

[DaleC]

Interesting discussion. I find the preoccupation with deco theory in rec diving to be fascinating but practically unnecessary. If there were an undue number of DCS cases in that arena while following established protocols I might think different.. but there isn't. What I do read is some people trying to tweak their BT by using DS's to allow pushing limits (time/repetition) which leads me to wonder about what other light deco planning is/isn't going on.

Rec diving is very safe when one keeps it simple. Stay away from the NDL's. If you push them, don't do so repetitively, over a series of days. In my mind, inventing DS's as way to counteract this is using a bandaid over poor practice. Some other people promote stops as a way to slow ascent rate - same thing. Deal with the problem, don't address it with an artificial construct.

Someone asked what is the risk in doing them? There is no intrinsic risk to doing a deep stop of itself (also no reward) but the misapplication can have consequences. In the first few posts I read an actual formula for calculating recreational deep stops which may/may not have been calculated incorrectly. What? Formula for rec diving? Others may not reserve enough gas to both push limits and do deep stops and go OOA at depth. Others may have buddies unprepared to do the same profile as them, thus leaving them alone at depth.

In the end, what could possibly go wrong with over complicating a proven, perfectly simple, safe system like the shallow depth safety stop with time extended for conservatism. What behavior are we really fixing with deep stops.

This is something I have come to believe: The technifying of recreational diving removes the core premise that makes it safe. Direct ascent to the surface always being an option. The closer you are to it, the safer you are. When you have a choice, all things being equal, dive shallow. If you choose to dive deeper eliminate anything that blocks direct access, overheads (real or virtual), practices. If you choose to voluntarily incur such overheads, do so with the comprehensive planning needed to compensate for the loss of direct access.

It's a scale of increasing risk. If ones diving always takes them to the deep end of the pool in this regard, one should be able to self question why that is, especially if diving is only meant to be a fun activity.