Reasons to do "Minimum Deco"

[Blackwood]

I'm not sure this is appropriate to "Basic" scuba discussions, but in the "basic" world of recreational diving, I think the benefits would be so minor as to be statistically unmeasurable.

To me, a primary benefit is one of practicality.

Using this method:
a) one doesn't need to track residual nitrogen, and
b) since there is only one limit for each 10 foot interval (rather than a large array of times at depth), the entire table is very easy to commit to memory.

The argument that all dives are deco dives is of course literally correct, but recreational diving has been developed so that a direct ascent to the surface is possible at all times with minimal risk of the bends.

C.

A direct ascent at or below a specific ascent rate. In other words, there is a minimum amount of deco.

If you dive to 60 feet on a 60fpm table, your "NDL" is predicated on 1 minute worth of in-water decompression.

Minimum Deco is a more appropriate term than No Deco.

 

[JeffG]

This came up almost 7 yrs ago

http://www.scubaboard.com/forums/basic-scuba-discussions/15352-15-safety-stop-vs-minimum-deco.html

 

[Reg Braithwaite]

Part of min deco is that after a 1 hour surface interval the whole thing resets. That means I just need to know the NDL table which is a simple depth=>time relationship, follow the min deco procedure, and take a 1 hour SI. No need to figure out what pressure group you are in, residual nitrogen levels, etc.

Using this method... one doesn't need to track residual nitrogen

I was hinting at this when I said:

off-gassing in the water is better than off-gassing on the surface.

If you do a dive in such a way that your protocol calls for a different "nitrogen group" after your surface interval, you have not completed your off-gassing before making the next dive.

Whereas if you do more off-gassing in the water, you are presumably able to complete your off-gassing within an hour. Hand waving over what to do if you need to get in the water before an hour has passed, doing more off-gassing in the water means you can complete your off-gassing within the one hour surface interval. That's a good thing!

 

[Reg Braithwaite]

This came up almost 7 yrs ago

http://www.scubaboard.com/forums/basic-scuba-discussions/15352-15-safety-stop-vs-minimum-deco.html

What I find interesting about that thread is a basic assumption that an agency should teach a single protocol that must work for a diver just emerging from their first OW class right through the end of their career.

Whereas in theory at least a PADI OW diver should not be doing dives deeper than 60' until they get their deep specialty or AOW card thingie. So I don't agree at all that you can dismiss a protocol because it is too difficult for the new diver to execute on their very first dive out of OW certification. Why not teach a new protocol when you get your deep or AOW?

Also, I appreciate the link but in my reading so far it seems to revolve around the hard science of deco and avoid the soft benefits like the fact that it is a very pleasant way to end a dive and that it is a good way to get some basic skills practice on every non-trivial dive.

Quite honestly, those reasons are just as meaningful to me as the (possibly placebo) perception of feeling better after multiple dives in a single day.

 

[Thalassamania]

...

The min deco seems to be a bit excessive?

It is excessive if you have a hot date waiting at the surface, it may not be excessive if you are fully appreciative of you spinal column and are attached to bladder, bowel and sexual function.

 

[M_Bipartitus]

I would like to know the justification of why min deco allows for no adjustment in dive profile for dives after a 1 hour interval. This would seem to indicate that there are no considerations for 60 or 120 minute tissues as they would not have enough time to desaturate. Is the assumption that over the course of repetitive min deco dives that there is not enough time at depth to accumulate in these tissue compartments, or that off gassing on this time scale is limited by bubble dynamics and the deeper stops have limited these bubbles?

... if you are fully appreciative of you spinal column and are attached to bladder, bowel and sexual function.

Not to get off topic, but I'm curious about where this type of expression comes from. I've heard it, or something very similar, several times, but only really from academic divers. Was it someone from AAUS, Lee Somers, yourself?

 

[Thalassamania]

I think that was Lee (or quite possibly Huggins), my description was often: "my spinal column has been berry, berry good to me."

 

[Reg Braithwaite]

I would like to know the justification of why min deco allows for no adjustment in dive profile for dives after a 1 hour interval. This would seem to indicate that there are no considerations for 60 or 120 minute tissues as they would not have enough time to desaturate. Is the assumption that over the course of repetitive min deco dives that there is not enough time at depth to accumulate in these tissue compartments, or that off gassing on this time scale is limited by bubble dynamics and the deeper stops have limited these bubbles?

Okay, this is where I personally draw the line in "Basic Scuba," although you may find others willing to get into it. I am trying to describe what I do and why I think it's a benefit. How it works and whether you have confidence in it is a much more complex subject. Please note that I have not claimed that the standard 15' safety stop doesn't work as advertised, just that my personal experience has been that sub-clinical DCS symptoms (which are NOT DCS) seem to have gone away for me when I switched.

I could blather on, repeating what I've learned cyber-diving and taking the UTD Ratio Deco course about bubbles and surface tension, and the link to DAN research discusses why the slow compartments may not be relevant for "recreational" dives (hint: Perhaps the difference between a recreational and "decompression" dive is whether the slow tissues are relevant).

But honestly I'm not qualified to do so. I honestly trust the PADI protocol to do a certain thing, my computer's algorithm to do a certain thing, and Ratio Deco as applied to minimal deco dives to do a certain thing. I selected Ratio Deco because I prefer what it does for me, not because I fundamentally distrusted either of the other choices available to me.