DECOMPRESSION CONTROVERSIES - Dr Simon Mitchell Briefing (Video)
Wondering what algorithms you use, and why?
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DECOMPRESSION CONTROVERSIES - Dr Simon Mitchell Briefing (Video)
Wondering what algorithms you use, and why?
not quite 40/80, but certainly favor shallow stops. With a controlled ascent profile, I don't think there is any reason to be concerned about deep stops
I suffered from fatigue when diving, and found "Pyle stops" on research. That made huge difference for me.
I'm not willing to give up my 2-minute midway . . .
But I let the Petrel's 40/80 rule . . .
I started cave/deco training with vpm, and I see no reason for me to change to anything else. I haven't done any really long hangs yet, but on +2 or 3 for conservatism I've never felt even slightly fatigued after several dives in the same day. Most of my dives do seem to end up with a profile that causes a quasi deep stop though (front section of devil's, top of the superstructure on a wreck, etc).
I dive a 40/85 or 40/80. I skip deepstops as I feel better after deep dives.
Maybe interesting, but in German: https://techdiving-network.de/wp-con...deco_et_al.pdf
It is about when ratio deco becomes aggressive.
JRT EDIT: Completed the link to make it clickable.
I wish you had added another category, which is self created algorithm. That is the person who dives any algorithm, but will "pad" stops by adding extra time. If I understand the research correctly, this practice from what I read is fairly common,does have a tendency to introduce other ongassing issues of certain compartments.
I would be interested in finding information that could be titled "Gradient Factors for Dummies." Something that would help generate enough knowledge to lead into deeper level materials. Any suggestions?
Thanks,
Greg
I checked "other."
I don't need any fancy algorithms; I just ascend slowly and stop a while. "I can feel the nitrogen leaving my body."
..
I have seriously known the quoted bit to be said.
Also: good poll.
Other?Quote:
Originally Posted by Kelly Jessop
Quote:
Originally Posted by GregO
Greg,Quote:
Originally Posted by Jax
Please check out Dr Mitchell's video in the above thread. Yes, it is long, but he has an excellent walk-through for Gradient factors.
What was the old Bill Royal algorithm? Dive till it hurts, hang till it stops?
Granted that I am only doing Nitrox above 130'.
I have been using Buhlmann computers and adding "Pyle" deep stop (safety stop).
Given that I am using redundant computers that track any slow tissue "on-gassing" or reduced off gassing that results from extra safety stops, AND factor extra tissue loading into my decompression obligation-
Can anyone offer reasonable thoughts as to potential "down side" of extra safety stops? Other than extra 5 min deco time.
I see absolutely no contradiction to adding a bit of RBGM onto a gas model. I have never seen an argument (aside from added time) that says you HAVE to take your supersaturation right up to the limit when using gas model decompression.
http://www.rebreatherworld.com/showt...rs-for-DummiesQuote:
Originally Posted by GregO
http://www.diverite.com/articles/gradient-factors/
https://decodoppler.wordpress.com/20...lified-primer/
http://www.alertdiver.com/Gradient_Factors
There's a great article written by the GUE folks on it, too... but I can't find it and I'm at work and should be doing... you know... work.
Edited to add: I found the GUE article I was thinking of. It had nothing to do with gradient factors at all. (Unsurprising, really. I don't know why I thought GUE would be writing anything about GFs.) It was about hyperbaric oxygen.
Quote:
Originally Posted by GregO
Here you go:
"Gradient Factors for DummiesGradient Factors for Dummies
By Kevin Watts
This article attempts to provide a user's view of gradient factors, an Erik Baker derived method of calculating decompression schedules. The title is not meant to be derisive, but simply an indicator that this article is meant to be a primer.
Back to Buhlmann
Everything in the gradient factor decompression algorithm revolves around Buhlmann’s tissue model. Currently this means 16 hypothetical tissue compartments (TCs) that are constantly tracked during a dive in order to determine each TC's inert gas pressure.
As you ascend all those TCs start to release pressure ("off- gas"). The question is "How fast can you let those TCs off-gas?"
Buhlmann answered that question by coming up with an “M-value”. Basically, an M-value is a maximum pressure value (different for each depth and tissue compartment) that tells you, if you exceed that value, Buhlmann thinks you’re crazy and believes you're about to get bent.
A natural ascent strategy, then, would be to move up in the water column until the pressure in your TCs just reaches Buhlmann’s M-value and then let your TCs off-gas a bit, rise to the next level, etc. In this strategy, you would keep going up in such a way that you never let your TCs exceed Buhlmann’s M-value.
Unfortunately, decompression illness does not exactly track Buhlmann's M-values. More sickness occurs at and above the pressures represented by M-values and less sickness occurs when divers never reach Buhlmann’s M-values.
Enter Gradient Factors
Gradient factors (GFs) were invented to let the diver choose how fast, and how close, their TCs get to Buhlmann’s M-values.
Gradient factors are calculated as follows:
What does this formula tell us?
First, the gradient factor formula tells us that at a GF=1.0, you are at Buhlmann’s M-value. Therefore, staying at or below GF=1.0 seems important. Second, it tells us that when our tissue compartment pressure just reaches ambient pressure, then the GF=0.0.
Another ascent strategy, then, might be to shoot up to a GF=0.8 and ascend in such a way as not to exceed that value. In this way you know that your tissue compartments are never over 80% of the distance between ambient pressure and Buhlmann’s M-value. In essence, you have a 20% safety margin on Buhlmann's M-values. Dive computers implementing GFs usually let you set two GF parameters. Moving straight to GF=0.8 and ascending in such a way that you always keep your TCs at GF=0.8 would be equivalent to setting your dive computer to 80/80.
Erik Baker's Strategy
Erik Baker didn't like the idea of ascending directly to a GF close to Buhlmann's M-Value. Instead he said, “Let’s all ascend first to a lower GF, then slowly move to higher GFs.” So, let’s say you want to first ascend to a GF=0.30 and then slowly move to reach GF=0.85 as you surface. This setting on your gradient factor computer is 30/85. In fact, my Shearwater computer uses 30/85 as it's default setting.
So what is happening when you use a GF setting of 30/85?
First your dive computer allows you to ascend until the pressure in your TCs first reaches a GF=0.3. This means your TC pressure is 30% of the way between ambient pressure and Buhlmann’s M-value. Then you sit there until your TCs drop enough pressure so that you can ascend to your next stop.
How much pressure must leave your TCs before you can ascend?
Assume you hit your first stop (GF=0.3) at 110 ft. Well, then, we now have two known points. Point 1 is (110,0.3), that is, at 110ft we are at a GF of 0.3. Point 2 is (0, 0.85), that is, at the surface we want to be at a GF=0.85. A natural way to ascend (and this is what Baker did) is to create a line from those two known points and ascend in such a way that you never exceed the GF generated by that line.
Once you've determined your two points, the formula for the maximum GF at any depth is:
But, since the high gradient factor is reached at the surface, HiGFDepth=0. So,
Therefore, if you hit your first GF=0.3 at 110ft, then your LowGFDepth=110. Before you can ascend to 100ft you must let off enough TC pressure so that when you arrive at 100ft the GF of your TCs does not exceed 0.35 calculated as
You can ascend to 90ft when your TCs let off enough pressure at your 100ft stop so that when you reach 90ft your TC's GF does not exceed 0.40 calculated as
The GF method allows you to ascend by walking that line all the way to the surface.
Summary
If you understood the above explanation, then you see why divers on RebreatherWorld say that setting your GF parameters to 10/90, or 10/80, etc. helps generate deep stops. The low GF of 10 means a stop must be generated when your TCs are only 10% of the way between ambient pressure and Buhlmann’s M-value, rather than 30% if you were to set the low GF to 30. Simply, the GF line just starts deeper.
The gradient factor method is a natural extension of Buhlmann's tissue compartment model. Diver's using computers implementing the gradient factor method should understand how modifying their GF parameters will alter their decompression profiles. My understanding is that it may be wise to consider altering your GF parameters based on dive characteristics, your physical condition, and your general attitude toward the risk of decompression illness. The gradient factor method provides the diver substantial flexibility in controlling their decompression profiles. Your responsibility is to choose the factors appropriate for you."
And obviously the Master piece.. not that difficult to follow either..
http://wrobell.it-zone.org/decotengu...ds/mvalues.pdf
and no offence intended, but when any diver has difficulties following and understanding these, such diver should cautiously limit their deco obligation, better not do deco overall..
That is my opinion to it
In regards to the poll. I opted for GF, favor shallow stops given the latest and greatest feedback in research and as a result positive results from divers changing their approaches.
I used to do the exact opposite though when I started, I chose my strategy favouring deeper stops and I even added Pyle stops on top of that in between..
I think the poll is a bit misleading as there is no such thing like "even GF".. I am not sure Jax how you chose the examples, but the even seem to match 100 overall when you actually add the numbers..
The favour shallow stops seems to exceed 100 while the favour deep stops seems to stay below 100..
Might be complete coincidence, might be a system..
Just a few comments to that.. when I alter/shift my stops from one side towards the other from a proven concept, then I try maintain the same overall decompression time a my overall concept..
So when I want to move my stops shallower I start moving up the low GF and then I resolve the hi GF to a value where I am close to the overall decompression time..
Doing it anyway different like just pushing up the Low GF and keeping the high GF at the old number etc.. will not only cause your depth of the stops being moved but you ARE EFFECTIVLEY changing the overall conservatisim of your decompression!
So one needs to be aware of that playing around with theses values..
Also apart from the choice of Lo GF + high GFs one needs to make up their mind on ascent speed before the first stop and between stops..
Here is something I have adapted from the (proven by the many dives conducted in the community as also succesful) Bubble model approach.. Rather than doing deep stops I am doing a consciously slow ascent until the first stop.. With Trimix there is the not faster than 10m/min recommendation anyways and that is what I do on Trimix but also on air I am not going faster..
Ascend speeds to your first stop will impact your feeling after decompression as well.. and maybe doing a slower overall ascent to first stop can eliminate the "need" for deepstops for you as well..
The default settings tend to be 30/70, and some people go with 20/80, etc. to set their range an equal amount less than the 100% line and above the 0% line. I don't know what to call it, but if anyone has a name for that????Quote:
Originally Posted by Nitrogenius
The two numbers don't really relate to one another and there's no reason to add them together, if that was where you were going?Quote:
Originally Posted by Jax
+1Quote:
Originally Posted by oya
so my observation on selecting these examples was correct..
of course the numbers relate to each other as they reflect the lo GF and the high GF so to some extend the frame you want to decompress in, but the relate to the M Values..
So a GF lo is not equaling a GF lo directly.. It takes a certain state of saturatuion that needs to be aqual as well in order to compare the two..
The same applies to the hi GF..
Even more you cant directly correlate the lo GF to the hi GF as the high GF very very sure will relate to a different M value as in fact your lead tissue will have shifted over the course of your decompression..
That is why I am dead serious about making sure to understand GF and understand M Values when you chose to use this decompression concept and even fiddle with it.
It has nor merit and value to add GF lo and hi to reach 100 and to stay over or under it..
Staying over it does not shift to shallower decompression and staying under 100 does not lead to deeper stops..
The depth of your first stop is only being affected by the GF lo.. the GF hi is irrelevant at this point (at least to the most extend it is soon coming into play determining the length of your first stop as you will need your terminal GF established to distribute the rest of the stops hence determining the length of each particular stop involving the GF concept)
There is some certain rule of thumbs approaches that involve looking at adding those to numbers and comparing them within a very limited frame, but essentially it really has NO MERIT whatsoever to add those numbers..
If at all you can characterize:
GF lo sets your relative depth of starting your decompression stops
GF hi sets your relative conservatism, but be weary that one influences the other so GF X/70 vs GF Y/70 never does represent the same level of conservatism of your overall deco.. The only thing it says is that your LEADING Compartment will have an MValue of equal or lesser than 70% of its allowed highest value according to Buhlmann original values..
It has no meaning as to the saturation level of other compartments (here the detail of the dive profile and decompression profile kicks in toghether with distribution over stop depths) other than being sure that no other compartment exceeds 70% of its permissible max M-Value...
To compare overall conservatism of decompression playing around with GFs the only method is to stay within the same overall decompression time umbrella.. this is how you shift from shallow to deeper stops and vice versa..
So the closest approach to the concept of an "even GF" would be to set a certain overall time you want to decompress in relation to a certain dive profile..
Hope this helps..
Negative.Quote:
Originally Posted by oya
There simply are people that move their gradient factor choice the same percentage from the absolute.
Bit of a correction:Quote:
Originally Posted by Nitrogenius
The GF high sets the conservatism on surfacing.
As opposed to low which sets the conservatism on the start of offgassing.
The only way to keep the same percentage from the absolute (the absolute being straight Buhlmann) is to have GFs of 10/10 or 20/20 or 80/80.Quote:
Originally Posted by Jax
Again, the GF low is a percentage of straight Buhlmann when your very first tissues start to offgass (others may still be ongassing).
The GF high is your percentage of straight Buhlmann on hitting the surface.
So if you were diving straight Buhlmann (100/100) you aren't diving 200 of anything. It's just that your M-Value is 100% the entire way up. When you adjust those numbers, or just leave them at 30/70 at some point you will be at 47% then at 63% of Bulmann's model of offgassing, then, as you ascend you'll get closer and closer to 70%. When you reach it at your last stop... your computer will tell you you are clear to exit the water.
So there is no rational value or point it trying to balance the two number to equal 100. Because it isn't 100 OF anything. They're two independently working points to create a "slope" of ascent.
Well just note that this approach has no merit whatsoever..Quote:
Originally Posted by Jax
Quote:
Originally Posted by oya
bit of a counter correction ;)
yes the GF hi sets the conservatism on surfacing to some extend.. But only in relation to the lead tissue/compartment..
Depending on what you had been doing before, your remaining tissues might be significantly more saturated with GF X/F versus GF Y/F with F being kept constant (hence I called it F for fixed)
That is actually what the whole NEDU study discussion is about..
So if you think that with moving your Deco strategy from lets us an example 10/80 to 40/80 that you are in fact maintaining the same level of conservatism at surfacing because you kept the GF hi constant, then you are very wrong with that assumption.
In fact your middle speed compartments will likely get a higher saturation level.. and hence the overall stress to the body might be higher and hence the decompression in fact be more aggressive and thus riskier..
In fact when raising your lo GF (from some point that works for you) you will want to reduce your GF to achieve the same "overall decompression/supersaturation stress over all tissues" when surfacing
In fact this is an area where staying costant in the sum of GF lo and hi might have some value.. I d still suggest to go via analyzing the overall decompression time and keep that constant..
The lo GF sure also stands somewhat for a conservatism on the start of offgasing in the most supersaturated tissue, but at the values used there and for the purpose they have been introduced I find the terminology conservatism a deceiving choice of words and not really representative..
Quote:
Originally Posted by oya
Right but one has to keep in mind that this slope is jumping between the leading compartments all over the place especially when altering the GF lo..
While for the first stop the relevant compartment and its M value will always be the same, the compartment "setting" the slope in comparison to the GF lo value is at a constant change..
It is not one slope we are dealing with but 16, when using GF with ZHL-16 or 8 when using ZHL-8 (if anybody does that)
So it is a bit comparable with jumping form 2 dimensional thinking into 3 dimensional..
This is what makes fiddling with GFs less easy as it appears at first sight and the main reason why GF X/F is not providing the same conservatism as GF Z/F
BTW finally watched Simons video..
Great summary on RBWs debate (where I had my share of "fun" dealing with ill perceptions of a certain bubble model programmer) back in late 2013 (at least before a lot of it had been censored).
You have to admire Simon that even with the heated debate his presentation is relatively unbiased and simply sticking to the facts established and being careful on explaining what it in fact does support and what not..
Cudos to this guy!
Unfortunately there was no bit of new info since then of which I had hoped for (like further real life reports of divers shifting the GFs from deeper stops to shallower stops)
BTW Simon states he is diving some 50/70, if I remember well he was coming from something like 25/85 or alike..
Note the reduction of the high GF along with it from the professional MD here.. And believe me he is not doing that to introduce a higher conservatism, but to keep it stable..
If I wasn't able to relay it properly, reach out to him I am sure he will respond and he will support what I stated here in regards to conservatism.. We ve been there many times in that +100 pages discussion back in 2013..
I'll not argue anyone's choices. :smt102Quote:
Originally Posted by Nitrogenius
I am not sure where the hang-on to this "sum to 100" came from - that was never expressed to me.Quote:
Originally Posted by Nitrogenius
It is simply that some people raise their Lo GF a certain percentage, and reduce their Hi GF the same percentage. That it adds to anything is coincidence.
Awesome stuff. Thanks!Quote:
Originally Posted by Nitrogenius
You don't have to argue anything there.. it was meant as an fyi to you and anybody else reading..Quote:
Originally Posted by Jax
If you are using GF macke sure you understand it and make your own conclusion on how to implement it.
When you do that then you will understand yourself the lack of merit to keep GFs sum at 100...
Good discussing, thanks!Quote:
Originally Posted by Nitrogenius
Does anyone here use different gradient factor settings depending on the planned depth and dive duration? i.e., which theoretical tissue compartments are controlling the ascent?
I do. The deeper/longer I go the more conservative the deco. More shallow time, less deep stops.Quote:
Originally Posted by Troglodyver
Explain the science or at least the logic on this practice. And define deep and long a little more.Quote:
Originally Posted by PfcAJ
Two specific dives might help, one from each camp.
I'm curious about this theory.
Thanks!
Bob
Sure no prob.Quote:
Originally Posted by floridabob
*Warning! I'm not a deco expert! I could be super wrong (and probably am).*
So my rationale is based on a few papers and some conversations with some decompression researchers. It my understanding that a given GF (say...30/85) doesn't produce the same probability of DCS across all depths and times. For instance, the risk of DCS you get from a 60min dive at 100ft is less than what you'd get from a 120min dive at 100ft. In a nutshell, as deco time goes up, probability of DCS goes up.
http://archive.rubicon-foundation.or...123456789/8233
http://archive.rubicon-foundation.or...pdf?sequence=1
To me, that's bad. I'd like to keep the probability of DCS 'flat' across all depth and time combinations. I'd ideally like to be able to control what the probability of DCS is. Both of those things are unobtainable with current commercially available decompression software :( But that doesn't mean that I can't manipulate the GF settings to result in more conservative decompressions.
Also, it looks like 'deep stops' aren't great. In my mind, deep stops proper stops (more than a few minutes) before deco gases. Anything less than that is a 'slow ascent'. Maybe the software generates '1,1,1,2' before the 1st gas switch. Fine. But when its more like '3,4,6,10'....ehh, I'd maybe rather be on a deco gas.
http://archive.rubicon-foundation.or...123456789/5069
So knowing those two things, I'd rather have a higher GF Low so I get to my deco gas sooner, and a lower GF High on long dives so I'm on oxygen a bit longer.
Imo, on a relatively short BT at modest depths, almost anything goes. A typical south florida wreck dive is a good example. 150ft, 30mins, 50%, 18/45 backgas. Sign me up for some 20/85 GFs. Its fine, its worked fine in the past, and it works fine for tons of divers. But on a longer thing that's a bit more out of bounds (like 130mins at 190ft plus a 30min transit at 50ft, or 100ft for 280mins)? I'll make some adjustments to more like 30/70. Not wild, but it adds some shallow time and ditches some time before the 1st gas switch. I know those are kinda two extreme examples, but if its more than an hour of deco I think about backing off a bit and shifting to 30/80 or 30/70, and I won't even play with VPM. Its all an experiment, anyways.
Fwiw, I'm not bothered by having the last oxygen stop be at 10ft or 20ft, and typically do the bulk at 20ft.
http://archive.rubicon-foundation.or...123456789/8966
IRT to VPM, it diverges from Buhlmann rapidly and I don't even mess with it.
Clear as diving behind Derek?
very sound approach in my eyes..Quote:
Originally Posted by PfcAJ
Looking at the current poll results:
GF Users seemed to have moved away from trying to create a exaggerated Deep Stop profile
Very little users of Bubble based models here in the cave community (which makes sense looking at the load profiles in cave deco diving over deep bounces like oftenly done in OW deep diving)
Concerning: Quite a lot of divers seem to believe in the "concept" of even GF..
Or maybe those values just by chance did align with what they are using`?
My Nitek HE uses Buhlmann ZH-L16 (no idea what the GFs are). Navy tables and EAN32 tables as backup for nitrox dives (along with bottom timer/ gauge). Trimix dive tables are generated with Buhlmann ZHL16/C with GF's of 30/85.
Here's an interesting exercise to visually demonstrate how little difference changes in gradient factors actually make in the shape of the deco profile. This is relatively easy to do in V-Planner or Multi-Deco and several other programs.
Plan a dive of say 300 fsw for 60 mins, which is deep enough and long enough to reflect some real differences. This just happens to be my go to profile for evaluating various factors and how they may affect deco. Using your typical bottom gas and deco gases for both, select two gradients factors that produce the same run times, one that represents a typical deep stop profile and one that represents emphasis on shallow stops as the latest research suggests. For example, 30/90 and 75/75 both have almost the same run times and are "radically different" approaches to decompression. Or are they? Plug these in and print out a depth/time graph of the resulting dive plans. Now overlay them and compare the actual differences. Yes, there are differences but I suspect most people will be surprised at how little.
Frankly, I dont know what works best. I do know that a dive of 70 minutes at 100 ft is probably more concerning than 70 minutes at 300. The He vs Nitrox debate ensues.
Boils down to this: 2% rate of DCS across all recreational dives. Profiles, depths, times, etc are nearly irrelevant. Still 2% rate. Meaning not commercial dives--as in what we do.
Not my numbers but DANs.
I was bent. I've seen divers bent. I've seen Bonus Deco. I've felt great and felt like crap. I have ZERO clue what works and even if it does today it may not tomorrow. So, do as you please and pay your insurance premium. Enjoy the problem free days and wonder WTF when you head to the chamber.
For me, the deeper/longer then the slower the ascent rate and the more He I prefer. And to do all your deco at 20....well, that's just a bit silly when you can watch what happens to your loop using an ECCR. Oh, and swim on deco and watch what happens to the off gassing.
Worthless, but so be it.
bob
So on a very deep, long technical dive you adjust your GFs to get you shallow faster? I don't mind the theory if it works for you. But please, don't call that being "more conservative."Quote:
Originally Posted by PfcAJ
iPhone. iTypo. iApologize.
Yea. Based on the papers I linked and the conversations I've had, that's correct.Quote:
Originally Posted by kwinter
Less deep time, more shallow time, and more time overall.
Quote:
Originally Posted by PfcAJ
And that is the part that makes it more conservative..
I had understood it that way..
of course just moving up shallower faster will not be more conservative, but less..
i.e. moving from a 20/F to a 50/F will be more aggressive as the overall deco time will go down..
Quote:
Originally Posted by jcr
I would argue that in fact it is already too long at this depth to provide significant differences..
After all GF are based on Buehlmann so it is the best base model.. tissue loading will be rather high hence lesser influence on the GF settings..
Would be really interesting to see some deco heat maps for that comparison though..
What's that mean to the people that know nothing of rb'sQuote:
Originally Posted by floridabob
constant PPO2 = always best mix..Quote:
Originally Posted by rddvet
no need to get to a certain depth for a specific gas switch..
I'm currently using 50/70 for deco dives. I'm experimenting with 70/70 & 65/65 on no-deco dives, but I haven't started using this on deco dives yet. I've also been known to occasionally use DCIEM tables - I haven't done this in some time, but I'm still not at the point of saying that I'd never use them. One other strange thing with me is that I only started using a computer for deco dives quite recently - probably about 5 years ago - before then it was tables,
Thanks,
Robert
This does not seem to make any sense to me..Quote:
Originally Posted by Robert Cook
Please explain?
It sound what you are saying an doing is that you cap a NDL dive at 70% respectively 65% of the Buehlmann model..
Not sure what the experimenting angle would be as when you use such settings and stay out of deco it says that you were diving vers well within NDL limits.. no more no less..
Or am I missing something?
Quote:
Originally Posted by Robert Cook
Just for fun: 70/70Quote:
Originally Posted by Nitrogenius
65/65Quote:
MultiDeco 4.10 by Ross Hemingway,
ZHL code by Erik C. Baker.
Decompression model: ZHL16-B + GF
DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = GF 70/70
Dec to 130ft (2) Nitrox 25 60ft/min descent.
Level 130ft 27:50 (30) Nitrox 25 1.23 ppO2, 122ft ead
Asc to 40ft (33) Nitrox 25 -30ft/min ascent.
Stop at 40ft 1:00 (34) Nitrox 25 0.55 ppO2, 36ft ead
Stop at 30ft 5:00 (39) Nitrox 25 0.48 ppO2, 27ft ead
Stop at 20ft 9:00 (48) Nitrox 25 0.40 ppO2, 17ft ead
Stop at 10ft 22:00 (70) Nitrox 25 0.33 ppO2, 8ft ead
Surface (71) Nitrox 25 -10ft/min ascent.
OTU's this dive: 43
CNS Total: 15.4%
142.0 cu ft Nitrox 25
142 cu ft TOTAL
DIVE PLAN COMPLETE
40/90Quote:
MultiDeco 4.10 by Ross Hemingway,
ZHL code by Erik C. Baker.
Decompression model: ZHL16-B + GF
DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = GF 65/65
Dec to 130ft (2) Nitrox 25 60ft/min descent.
Level 130ft 27:50 (30) Nitrox 25 1.23 ppO2, 122ft ead
Asc to 40ft (33) Nitrox 25 -30ft/min ascent.
Stop at 40ft 1:00 (34) Nitrox 25 0.55 ppO2, 36ft ead
Stop at 30ft 6:00 (40) Nitrox 25 0.48 ppO2, 27ft ead
Stop at 20ft 11:00 (51) Nitrox 25 0.40 ppO2, 17ft ead
Stop at 10ft 25:00 (76) Nitrox 25 0.33 ppO2, 8ft ead
Surface (77) Nitrox 25 -10ft/min ascent.
OTU's this dive: 43
CNS Total: 15.4%
147.4 cu ft Nitrox 25
147.4 cu ft TOTAL
DIVE PLAN COMPLETE
Quote:
MultiDeco 4.10 by Ross Hemingway,
ZHL code by Erik C. Baker.
Decompression model: ZHL16-B + GF
DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = GF 40/90
Dec to 130ft (2) Nitrox 25 60ft/min descent.
Level 130ft 27:50 (30) Nitrox 25 1.23 ppO2, 122ft ead
Asc to 50ft (32) Nitrox 25 -30ft/min ascent.
Stop at 50ft 0:20 (33) Nitrox 25 0.63 ppO2, 46ft ead
Stop at 40ft 2:00 (35) Nitrox 25 0.55 ppO2, 36ft ead
Stop at 30ft 4:00 (39) Nitrox 25 0.48 ppO2, 27ft ead
Stop at 20ft 6:00 (45) Nitrox 25 0.40 ppO2, 17ft ead
Stop at 10ft 12:00 (57) Nitrox 25 0.33 ppO2, 8ft ead
Surface (58) Nitrox 25 -10ft/min ascent.
OTU's this dive: 43
CNS Total: 15.6%
131.4 cu ft Nitrox 25
131.4 cu ft TOTAL
DIVE PLAN COMPLETE
Jax, the piece I was not getting was the experimenting fo GF values around NO DECO dives..
That is the angle that does not seem to make sense to me..
Your examples are all well within Deco dives..
The GF will in part determine whether or not it IS a dive requiring deco.Quote:
Originally Posted by Nitrogenius
What PfcAJ says reflects my understanding and approach as well. Moved from VPM-B to Buehlmann with GF (default 30/80) after reading the NEDU study. Purely subjective/anecdotal but tend to feel less tired when driving 3-4 hours back home from deeper dives in Lake Michigan after the switch.
Quote:
Originally Posted by MichelleC
Well that part is obviously understood..
Quote:
Originally Posted by Nitrogenius
But that would be it..
So essentially NDL dives will be conducted extremely conservative..
not much experimenting..
or is the experimenting angle a comparison against other Diving comps and other models. e.g. in comparing how much remaining NDL the other models/comupters still give..
because a 65/65 remaining out of Deco will have to be even more conservative than any Suunto..
Which NEDU study, please?Quote:
Originally Posted by midway
It's linked in AJ s post [emoji2]Quote:
Originally Posted by Jax
Sent via
:smt100Quote:
Originally Posted by Jack Hammer
Quote:
Abstract of the Undersea and Hyperbaric Medical Society, Inc. Annual Scientific Meeting, St Pete Beach, Florida, USA. (http://www.uhms.org)
Abstract of the Undersea and Hyperbaric Medical Society, Inc. Annual Scientific Meeting, Las Vegas, Nevada, USA. (http://www.uhms.org)
Or were you referring to the "Desktop Algorithms" Study? I was looking for an actual physiological study.
The Desktop Algorithms study was to me too lacking in sufficient parameters.
First - It is a Risk Poster. Information for posters is so concatenated (in my experience) as to be purely of information to some casual observer.
Second - "A" Goal in performing this . . . is to demonstrate . . . for the novice technical diver . . . the generally accepted trend . . ." does not = scientific.
Third - the software companies did not review or condone any of it.
Fourth - For such a general poster, it is full of percentages and estimates and .1 second ascents and . . . Nope. It's like measuring with a micrometer to cut with an az.
I think this is the one you're looking for
http://archive.rubicon-foundation.or...123456789/5069
Ah, yes - that was the one on air, where they were compressed to 170fsw.Quote:
Originally Posted by PfcAJ
Unfortunately, there wasn't a study document:Quote:
Schedule 1, with first stop at 40 fsw, was prescribed by the man-tested, deterministic gas content, VVAL18 Thalmann Algorithm. Schedule 2, with first stop at 70 fsw, was the optimum distribution of TST according to the man-dive calibrated, probabilistic BVM(3) bubble model. Decompression sickness (DCS) incidence with these schedules was compared under the sequential stopping rules of reject-high if DCS risk > 7% or reject-low if DCS risk < 3% with 95% confidence. RESULTS: The trial was terminated after midpoint interim analysis. Neither schedule was rejected, but DCS incidence in Schedule 2 (deep stops, 11 DCS/198 dives) was significantly higher than in Schedule 1 (3/192, p=0.030, one-sided Fisher Exact)
I would really like to see the deco plan for Schedule 1 and Schedule 2.Quote:
This was found in the UHMS abstracts community and there is no journal article or technical report associated with the abstract you viewed. Thank you for your interest. Please visit our FAQ page <http://rubicon-foundation.org/RRRfaq.html> --The Rubicon Team.
The VPM-B for the 170FSW for 27.2 minutes is
Quote:
MultiDeco 4.10 by Ross Hemingway,
VPM code by Erik C. Baker.
Decompression model: VPM - B
DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2
Dec to 170ft (2) Air 60ft/min descent.
Level 170ft 24:22 (27) Air 1.29 ppO2, 170ft ead
Asc to 100ft (29) Air -30ft/min ascent.
Stop at 100ft 0:28 (30) Air 0.85 ppO2, 100ft ead
Stop at 90ft 2:00 (32) Air 0.78 ppO2, 90ft ead
Stop at 80ft 2:00 (34) Air 0.72 ppO2, 80ft ead
Stop at 70ft 3:00 (37) Air 0.65 ppO2, 70ft ead
Stop at 60ft 4:00 (41) Air 0.59 ppO2, 60ft ead
Stop at 50ft 6:00 (47) Air 0.53 ppO2, 50ft ead
Stop at 40ft 7:00 (54) Air 0.46 ppO2, 40ft ead
Stop at 30ft 11:00 (65) Air 0.40 ppO2, 30ft ead
Stop at 20ft 67:00 (132) Air 0.34 ppO2, 20ft ead
Surface (134) Air -10ft/min ascent.
Off gassing starts at 123.8ft
OTU's this dive: 46
CNS Total: 17.7%
239.7 cu ft Air
239.7 cu ft TOTAL
GF40-90
The Abstract says the first bubble-stop was at 70 .. .. but what were the times?Quote:
MultiDeco 4.10 by Ross Hemingway,
ZHL code by Erik C. Baker.
Decompression model: ZHL16-B + GF
DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = GF 40/90
Dec to 170ft (2) Air 60ft/min descent.
Level 170ft 24:22 (27) Air 1.29 ppO2, 170ft ead
Asc to 80ft (30) Air -30ft/min ascent.
Stop at 80ft 0:48 (31) Air 0.72 ppO2, 80ft ead
Stop at 70ft 1:00 (32) Air 0.65 ppO2, 70ft ead
Stop at 60ft 2:00 (34) Air 0.59 ppO2, 60ft ead
Stop at 50ft 3:00 (37) Air 0.53 ppO2, 50ft ead
Stop at 40ft 6:00 (43) Air 0.46 ppO2, 40ft ead
Stop at 30ft 6:00 (49) Air 0.40 ppO2, 30ft ead
Stop at 20ft 54:00 (103) Air 0.34 ppO2, 20ft ead
Surface (105) Air -10ft/min ascent.
OTU's this dive: 43
CNS Total: 16.1%
202.2 cu ft Air
202.2 cu ft TOTAL
EDIT: :smt100 . . . How does one set the first stop to 40FSW?
I found this: http://archive.rubicon-foundation.or...pdf?sequence=1
Is it the same? It's June 2011.
Not the same, but looks like it. This one is titled
Abstract sure sounds the same!Quote:
REDISTRIBUTION OF DECOMPRESSION STOP TIME FROM SHALLOW TO DEEP STOPS INCREASES INCIDENCE OF DECOMPRESSION SICKNESS IN AIR DECOMPRESSION DIVES
Quote:
14. ABSTRACT
Classical decompression algorithms limit hypothetical tissue gas contents and prescribe decompression schedules with most of the total stop time (TST) allocated to shallow decompression stops. More recent bubble-model-based algorithms limit hypothetical bubble profusion and size and prescribe decompressions with TST skewed toward deeper stops. A large man-trial compared the efficiency of these approaches. Divers wearing swimsuits and t-shirts, breathing surface-supplied air via MK 20 UBA, and immersed in 86 °F water were compressed at 57 fsw/min to 170 fsw for a 30 minute bottom time during which they performed 130 watt cycle ergometer work. They were then decompressed at 30 fsw/min with stops prescribed by one of two schedules. The shallow stops schedule, with a first stop at 40 fsw and 174 minutes TST, was prescribed by the, deterministic, gas content, VVAL18 Thalmann Algorithm. The deep stops schedule, with a first stop at 70 fsw, was the optimum distribution of 174 minutes TST according to the probabilistic BVM(3) bubble model. Decompression sickness (DCS) incidence following these schedules was compared. The trial was terminated after the midpoint interim analysis, when the
DCS incidence of the deep stops dive profile (11 DCS/198 dives) was significantly higher than that of the shallow stops dive profile (3/192, p=0.030, one-sided Fisher Exact). On review, one deep stops DCS was excluded, but the result remained significant (p=0.047). Most DCS was mild, late onset, Type I, but two cases involved rapidly progressing CNS manifestations. Results indicate that slower tissue gas washout or continued gas uptake offsets the benefits of reduced bubble growth at deep stops
The above is titled EMPIRICAL EVALUATION OF THE EFFICACY OF DEEP STOPS IN AIR DECOMPRESSION DIVES.Quote:
Originally Posted by PfcAJ
I get the feeling the above was issued from the same actual study. :smt013
HOLY CARP!!!!
Will you look at the times spent at those deep stops????? No WONDER the poor devils got DCS!!
https://scontent.fphx1-2.fna.fbcdn.n...56&oe=57D24F03
Page 4, http://archive.rubicon-foundation.or...pdf?sequence=1
Quote:
Originally Posted by Jax
The very one Simon Mitchel had been referring to in that video of the conference speech you had posted in the other thread http://www.cavediver.net/forum/showt...riefing-(Video)
Quote:
Originally Posted by Jax
The whole purpose of the study was to provoke an indicative number of DCS in both decompression approaches..
Only then you would be able to make statictically meaningful comparisons..
Simon had all explained in his presentation and very objective..
What can be drawn from it and what cant
Fact is that the shallow stop profile showed less DCS
Note that the deep stops have been calculated with a Navi bubble model.. Same theory as in VPM..
It's the tech report entitled "Redistribution ..." that you mention a few posts down. The slides by Simon show pics of slow/fast tissue state/saturation aimed at advancing an explanation for the NEDU results. I have yet to look up the more recent results. It's important to note that the NEDU results are for depths in the 170 fsw range. As floridabob noted, dives in the 200+ ft range are another matter. I doubt there will be meaningful empirical results for such depths but there may be ways around it building on the NEDU results. For cave divers w/o trimix/AN/DP training (there appear to be some) I would encourage to read the NEDU study. It's a well-designed, sound scientifically meaningful study.Quote:
Originally Posted by Jax
I read it -- I don't know how or what kind of bubble model they were using, but that deco plan sucked spectacularly!Quote:
Originally Posted by midway
Could someone please explain how those 70fsw - 40fsw were "stops" and not just multilevel diving? Of COURSE they were on-gassing all that time!
Quote:
Originally Posted by Jax
BVM(3) a Navi Model the shallow deco was performed after VVal-18 also Navi Model
Bubble models are not about ongasing.. Buble models are about reducing bubble size.. hence the stops.. aimed at reducing potential bubbles..Quote:
Originally Posted by Jax
Jax, look into scientific method... and watch the video again by Simon Mitchell you linked. He explains it well
- Jeff
Perhaps one of those so-called 'experts' at NEDU? After all, they designed the study and from what you say clearly don't understand decompression physiology as well as you do.Quote:
Originally Posted by Jax
To paraphrase Joe Dituri (and others): the consensus of experts in the field is that DCS probably has something to do with bubbles.
Let me rephrase this - does anyone know the bubble model they used in this study?Quote:
Originally Posted by apitkin
I have had a bubble model Uwatec for years. It NEVER gave me *anything* like that. No deep stops have been more than a minute or two. So, will someone help me out with how a stop at 70 has twelve minutes?
This was a scientific study in controlled conditions designed to minimize/eliminate variables. It was not a random subjective comparison using a tech divers wrist computer. It really is explained, I thought well, in the Decompression Controversies video you linked. Have you actually watched that video? If so, watch it again and pay more attention. [emoji6]Quote:
Originally Posted by Jax
Again, spend a few minutes and read about what scientific method is and how it does not always look like the way the general population may go about things. I think it will help you to understand why things are done in what can seem to be an odd manner.
[emoji2]
- Jeff
Jax, while I always endeavor to be polite to my fellow CDF members, you're asking the wrong people to explain it. It's explained in the scientific papers and references at your finger tips.
And to be fair to you, you are probably not comparing apples to apples on these "deep stops".
Or maybe you are totally lost, who knows!
Bob
That is very possible. I would simply like to find "their" bubble model because it is nothing like the one I have. :-)Quote:
Originally Posted by floridabob
Well, I did learn a little bit about that scientific methods stuff in college. And when I picked up a specialty in determined Reliability, Availability, and Maintainability analysis. It is a bit of a requirement in engineering.Quote:
Originally Posted by Jack Hammer
What I did NOT find in the video - did I miss it? What was the bubble model that generated the huge deep stops that were actually in the study. I would really like to find that, but searches on the specified name from the paper are not coming up.
I believe the bubble model used was called BVM(3). ☺Quote:
Originally Posted by Jax
- Jeff
Yes, I know. I find discussions OF its use but nothing I can sink my teeth in. :( Thanks.Quote:
Originally Posted by Jack Hammer
If you are looking for a "calculator" you won't find it. However the BVM(3) model is well documented in the literature, although in its equational form. You being an "engineer", shouldn't have any problems with the handling the calculations required to come up with the schedules you would like to look at.....Quote:
Originally Posted by Jax
That is what I am looking for - the literature in which it is well-documentedQuote:
Originally Posted by TaraR
Jax, you, like others on the "deep stops" thread, seem to be missing the point. These are not schedules that anyone would actually use in practice. The study was designed to produce DCS and the profiles were exaggerated to produce statistically meaningful results.
You might have better means to access it than anyone else, given your service background..Quote:
Originally Posted by Jax
It is a Navi Model.. they do not share too much of their stuff ;)
BVM (3)
Quote:
Originally Posted by jcr
The way I understood it though was that the model actually would have been intended to being used..
For sure though within the model the stops were accentuated to make differences statistically relevant..
BTW.. Jax a certain programmer of a widely used bubble model would love your argument..
He was claiming that these profiles have nothing to to with Rec-Tec diving and thus there are NO conclusions to be drawn from the test..
Neglecting the designed approach to the study..
And please look at the heat maps in the video of Simon..
Or go to the source that thread at RBW.. it is still there.. Just some stuff might not appear to make sense anymore due to the heavy cencorship after the fact, but it is still there..
loadfs of comparison heat maps have been produced and actually using "conservative" profiles with current models, that rec-tec divers would actually dive..
that is in the video as well though..
Thanks!Quote:
Originally Posted by Nitrogenius
Yes, they are probabilistic models that can produce schedules you could actually use but for the purposes of the study the probability of DCS was significantly increased. No one associated with the study is suggesting that these are schedules anyone would use in the field.Quote:
Originally Posted by Nitrogenius
Man! But I am confused. Don't you guys use computers?
Or are you contemplating writing your own programs? Cause frankly I think the way people feel is so anecdotal and subjective that you could spend your remaining days varying your conservatism and M values and never think anything changes.
Bob
You see, that is why *I'm* confused. My bubble model algorithms don't produce anything like the table produced in the NEDU study. So, I would like to see what their algorithm is . . .Quote:
Originally Posted by floridabob
I understand the algorithm Uwatec uses, and have been able to simulate it so I understand how it works. So, the BVM(3) model . . . I don't get it. The 70fsw - 40fsw stops add over 45 minutes of bottom time . . . and therefore more deco time.
I am confused on how they chose such a model.
Didn't you watch Joe Dituri's deco talk? Actually nobody really understands deco theory. Dr Zumrick (a generation before Dituri) always said that there is no way to mathematically predict DCS, and I don't see that anything has changed. I use what was recommended by Shearwater (30/70 IIRC), and follow it. I have never had a problem (knock on wood). I tried cutting tables for awhile, but caves aren't like the ocean. You don't get to pick a depth, and go to it, then ascend by the tables.Quote:
Originally Posted by Jax
Perhaps you may want to consider emailing the authors directly.Quote:
Originally Posted by Jax
- Jeff
.... heading directly towards the failed A2 NEDU profiles.... hypocrisy in action - got to love it.Quote:
Originally Posted by PfcAJ
I did, of course, and deco theory is a crap shoot.Quote:
Originally Posted by FW
That doesn't mean that I should not want to understand the argument and discussion. I recognize many others don't care.
I will do that, once I have educated myself enough to ask a (some) logical question(s). It's unprofessional to expect a one-on-one 'teach me' discourse. They deserve an informed audience.Quote:
Originally Posted by Jack Hammer
Oh Geez... here we go again... :popcorn:Quote:
Originally Posted by rossh
- Jeff
Ross's two posts on CDF:Quote:
Originally Posted by rossh
1 to peddle his software
1 to snipe at the NEDU study.
Do the heavy hitters really have to come to third (or was it fourth?) forum to lay it all out and make you look like a clown again? I guess its been a few months and you've had time to forget how embarrassed you were.
Quote:
Originally Posted by rossh
Chill, please. Let us have a respectful, even if disagreeable, discussion.Quote:
Originally Posted by PfcAJ
Hmmm, and both posts in violation of rules. rossh, consider this a warning. Rule #2 No Soliciting, Rule #6 Comments about individuals, agencies, organizations, political parties and businesses will be removed if found to be inflammatory or cause the discussion to be uncivil.Quote:
Originally Posted by PfcAJ
You can't seriously go after him for something he may or may not have broken five years after the fact?Quote:
Originally Posted by FW
No, but I can warn him if he does it again, he won't slip by next time.Quote:
Originally Posted by jlillest
Sounds good, you've got until 2021 to warn him! :PQuote:
Originally Posted by FW
Thank you, except the second post is about a planning method, and a study test / result, in a thread to discuss deco. Your warning is a little off the mark I think.Quote:
Originally Posted by FW
Oh leave the poor guy alone. He already got beat up Rebreatherworld, CCR Explorers, Scuba Board, and The Deco Stop...
I think Robert Osborne should use him as a case study. :)
Sent via
Quote:
Originally Posted by Jax
That doesn't matter.. what matters is the conclusions drawn by Simon Mitchel and tissue analysis of actual Tec-Rec diving computer produced schedules (i.e. VPM-B +8 vs a correlating ZHL-16 GF schedule with less emphasis on deep stops)
It is pretty obviousl were the differences in the "middle speed" tissues are and that the bubble model approach overall causes more decostress which quite likely might produce more DCS..
Overall note that this is all much more relevant for Ocean Deep Bounce diving than it is for moderate depth long cave dives (and the resulting deco) and even less for deep caves with long bottom times..
Long bottom times at great depth generate very similar deco profiles between bubble and tissue models anyways as overall saturation throughout all compartments gets fairly high..
Not that I have experience in deep and long (only deep and short and somewhat shallower and long), but that is my take from playing around with the models and my conclusion drawn as why this little difference is happening
Quote:
Originally Posted by Jax
Don't be.. The reasoning is in the approach of the test to actually trying to generate differences and statistically relevant numbers of DCS to be able to compare..
No more no less
+1 .. just thought the same..Quote:
Originally Posted by Jack Hammer
Well he already has Jax on his side it seems ;)
grasping at strawers I guess.Quote:
Originally Posted by PfcAJ
But shouldn't be too worried.. for cave profiles it really has less effect..
So business is somewhat protected already..
sorry for the many posts.. have been reading through it..
Will stop now..
No need to warn..
I govern myself accordingly :)
Hey, I'm on no one's side! :DQuote:
Originally Posted by Nitrogenius
I just want to understand.
Sure, but you had been arguing the same train of thought as he did in the past..Quote:
Originally Posted by Jax