UTD Ratio deco discussion

[Kevrumbo]

Really? You mean compared to what they did in the past, I assume, but not in comparison to other algorithms.
Look at the comparison of a RD 2.0 profile to the Buhlmann profile I provided earlier.

As you can see:

• In both cases, RD made the first stops much deeper than the Buhlmann profile.
• In both cases, the RD profile spent 10-11 minutes more time in the deepest portion of the dive than the Buhlmann profile.
• In both cases, the RD profile spent less time in the shallow stops than the Buhlmann profile. At sea level, it spent 5 fewer minutes. At altitude, it spent 16 fewer minutes.

So, how is this evidence that the RD profile protects the faster tissues by slower ascents and then makes up for it by extending the shallower stops to compensate for that extra time at depth?

John, the RD profile above is not necessarily set in stone; the user has the prerogative to make an informed decision in adding more shallow O2 time if he wants to. To optionally track it with a Perdix/Petrel Computer, the user can lower the surfacing GF from 85 to something like 70 for instance, to quantitatively extend the O2 profile.

What matters in light of the NEDU Study . . . As the practical solution is with any Bubble Model algorithm of which UTD's RD had the history of the longest & deepest of all deepstops, a deco diver is gonna have to extend & pad the O2 deco stops to effectively decompress the surfacing slow tissue tensions if still choosing to use RD.

. . .Getting off the bottom (that is, skipping the deep stops) can reduce tissue loading in intermediate and slow tissues. No matter what is done at depth, prolonging shallow stop time is effective at reducing VGE in individuals predisposed to develop them. Other strategies might work, but I am most impressed by those based on credible evidence. I call prolonged shallow stops really cheap insurance.

Neal Pollock Ph.D

Objectively, I think just in general, the above advice is a practical option for any deco algorithm in use.

 

[boulderjohn]

ohn, the RD profile above is not necessarily set in stone; the user has the prerogative to make an informed decision in adding more shallow O2 time if he wants to.

So, what kind of training is offered so that the diver can make an "informed decision"? What is the source of this information?

It goes back to my question asked many times so far about altitude. We have heard several times that individual UTD instructors are telling their students that if they are to dive at altitude, they have to make adjustments to RD, but we are not told what those adjustments are. I got the distinct impression that the instructors don't know what those adjustments are, either.

At what point in the training are they taught how to make those informed decisions?

 

[Kevrumbo]

So, what kind of training is offered so that the diver can make an "informed decision"? What is the source of this information?

It goes back to my question asked many times so far about altitude. We have heard several times that individual UTD instructors are telling their students that if they are to dive at altitude, they have to make adjustments to RD, but we are not told what those adjustments are. I got the distinct impression that the instructors don't know what those adjustments are, either.

At what point in the training are they taught how to make those informed decisions?

Probably at the point when a particular dive team actually has to actually use current RD 2.0 methodology at altitude John. (I haven't heard about any UTD Lake Tahoe deco dives lately, nor read any recent reports from BAUE).

From what @mikeny9 and @decompression have described, it sounds unofficially like "Cross Correction" formulas within the Ratio Deco 2.0 paradigm:

For a given altitude A, the atmospheric pressure Pa (in atm) at that altitude is

Pa = (1 atm) * exp(5.255876 * ln(1 – (C * A))).

where C = 0. 0000068756 / 1 foot = 0. 000022558 / 1 meter,
depending on whether the altitude is given in feet above sea level or in meters above sea level.

With a calculated Pa (Pressure at Altitude determined from the above equation) and given Da (actual depth at Altitude in ffw), we have the general equation below giving Theoretical Ocean Depth (TOD), and with it we can use the dive tables that are based upon diving in the ocean, such as the UTD Min Deco/NDL Table or Cascading Ratio Deco Schedules:

TOD = Da * (1 atm / Pa) * (33 fsw / 34 ffw);

or TOD = Da * (1 atm / Pa) * (10 msw/10.3 mfw).

Figure out your adjusted depth deco profile using RD methodology, compare it with other deco software algorithms at altitude for the given actual depth and bottom time, and add more conservatism as necessary especially if you plan to incorporate deepstops to control fast tissue supersaturation- i.e. extending out a shallow O2 deco stop to further reduce the resultant decompression stress on the slow tissues, especially when surfacing at a lower ambient pressure at altitude.

 

[boulderjohn]

Probably at the point when a particular dive team actually has to actually use current RD 2.0 methodology at altitude John. (I haven't heard about any UTD Lake Tahoe deco dives lately, nor read any recent reports from BAUE).

From what @mikeny9 and @decompression have described, it sounds unofficially like "Cross Correction" formulas within the Ratio Deco 2.0 paradigm:
...
Figure out your adjusted depth deco profile using RD methodology, compare it with other deco software algorithms at altitude for the given actual depth and bottom time, and add more conservatism as necessary especially if you plan to incorporate deepstops to control fast tissue supersaturation- i.e. extending out a shallow O2 deco stop to further reduce the resultant decompression stress on the slow tissues, especially when surfacing at a lower ambient pressure at altitude.

It sounds as if you are guessing what UTD would do. I would hope that someone would know what UTD officially teaches. So far, no one knows.

What you describe, BTW, is a policy of "Do a lot of math and then make your best guess." I find it hard to believe that would be an official policy.

I know there are UTD instructors following this thread. In a couple of days, I will be diving with people in Santa Rosa, NM, at an elevation of about 4,600 feet. If you wanted to join us, what would you do for dive planning?

 

[Kevrumbo]

It sounds as if you are guessing what UTD would do. I would hope that someone would know what UTD officially teaches. So far, no one knows.

What you describe, BTW, is a policy of "Do a lot of math and then make your best guess." I find it hard to believe that would be an official policy.

I know there are UTD instructors following this thread. In a couple of days, I will be diving with people in Santa Rosa, NM, at an elevation of about 4,600 feet. If you wanted to join us, what would you do for dive planning?

For a given altitude A, the atmospheric pressure Pa (in atm) at that altitude is

Pa = (1 atm) * exp(5.255876 * ln(1 – (C * A))).

where C = 0. 0000068756 / 1 foot = 0. 000022558 / 1 meter,
depending on whether the altitude is given in feet above sea level or in meters above sea level.

With a calculated Pa (Pressure at Altitude determined from the above equation) and given Da (actual depth at Altitude in ffw), we have the general equation below giving Theoretical Ocean Depth (TOD), and with it we can use the dive tables that are based upon diving in the ocean, such as the UTD Min Deco/NDL Table or Cascading Ratio Deco Schedules:

TOD = Da * (1 atm / Pa) * (33 fsw / 34 ffw);

or TOD = Da * (1 atm / Pa) * (10 msw/10.3 mfw).

Pa = (1 atm) * exp(5.255876 * ln(1 – (C * A))). C= 6.8756E-6, Given A=4600 ft.
Pa = 0.844

So given a dive for example to Da = 60 ffw:
TOD = Da * (1 atm/Pa)* (33fsw/34ffw) = 68.9 fsw (approx 70fsw).

UTD Min Deco Table at 70 fsw, NDL Time is:
35min for Air; 45min for Eanx32.

Safety Stop 20 fsw => 17 ffw
Safety Stop 10 fsw => 9 ffw
(Solving for Da in ffw from TOD formula above)

-----------
TOD's for actual depths in ffw:

50 ffw => 57.5 fsw
60 ffw => 68.9 fsw
70 ffw => 80.4 fsw
80 ffw => 91.9 fsw
90 ffw => 103.4 fsw
100 ffw => 114.9 fsw
110 ffw => 126.4 fsw

 

[PfcAJ]

If you wanted to join us, what would you do for dive planning?

Step 1 - Ensure DAN is paid up
Step 2 - ???

 

[JohnnyC]

Step 1 - Ensure DAN is paid up
Step 2 - ???

What would the GUE RD procedure be for a dive that BoulderJohn wants to do? Is there a procedure?

I only use RD (old Tech 1 style as taught to me by a friend) @ 1:1 for 45m or shallower stuff as a backup to backups, so it's all relatively easy to come up with an emergency ascent profile and just pad it beyond 1:1 on the shallow side. Which realistically means I'd have to have a failure of two Shearwaters AND lose my wetnotes and bottom timer..... In my case for altitude, I'd probably just cut another set of tables and keep them in another pocket. I have yet to get any exposure to altitude compensation and using RD so I'd just avoid it and err on the side of diving super conservatively.

 

[PfcAJ]

What would the GUE RD procedure be for a dive that BoulderJohn wants to do? Is there a procedure?

I only use RD (old Tech 1 style as taught to me by a friend) @ 1:1 for 45m or shallower stuff as a backup to backups, so it's all relatively easy to come up with an emergency ascent profile and just pad it beyond 1:1 on the shallow side. Which realistically means I'd have to have a failure of two Shearwaters AND lose my wetnotes and bottom timer..... In my case for altitude, I'd probably just cut another set of tables and keep them in another pocket. I have yet to get any exposure to altitude compensation and using RD so I'd just avoid it and err on the side of diving super conservatively.

Put parameters in decoplanner (or whatever), see if there's a handy ratio. Make tables. Go dive.

 

[boulderjohn]

Put parameters in decoplanner (or whatever), see if there's a handy ratio. Make tables. Go dive.

That's pretty much what Jarrod told me years ago.

The difference when I was with UTD was that they did not think any of the desktop programs were any good, and we were told to ignore them. That is why I am still trying to find out what they do now officially. I have seen people guessing, and I am just surprised no one seems to know for sure.

 

[PfcAJ]

That's pretty much what Jarrod told me years ago.

The difference when I was with UTD was that they did not think any of the desktop programs were any good, and we were told to ignore them. That is why I am still trying to find out what they do now officially. I have seen people guessing, and I am just surprised no one seems to know for sure.

Why did they not think any programs were good?

Just saying something doesn't make it true.

The entire premise of UTDs deco teachings seem to be based on appeal to authority.