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Hi

Are these two the same thing?

Is the case for Deep Stops now acceptably proven? As far as anything is in this theory driven sport. Can anyone point me at comparison material please that should give confidence for adopting them.
Rgds
Wibble
 

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No. 1 - They are the same thing

No. 2 - I'm sure someone will be along soon with a plethora of links, but in the mean time, have a look at Mark Powell's (member here) website

No. 3 - I did lots of personal testing and have definitely come to the conclusion that they work for me - tested to 101m on a couple of occasions and widely tested on dives to 80m

Ultimately, what works works, and in my opinion they are a very very good thing.

Juz
 

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Finless: You couldn't invent him...
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No. 3 - I did lots of personal testing and have definitely come to the conclusion that they work for me.

Ultimately, what works works, and in my opinion they are a very very good thing.

Juz
Ditto at shallower depths - 40mtrs.

Wibble. Have you read the Richard Pyle story (excerpt?) .......... I read it and introduced them immediately to my dives. I think I felt better after dives with deeper stops which, I suppose, is a good enough reason to use them?

I know the deep stops are a feature of Proplanner.

I never really understood or wanted to understand the theory of gasses in the blood etc etc. All I wanted was not to be the first to try some theory and for somebody I knew of and had some respect for and who does lots of diving to say this is an OK way to do things. If I recollect, Richard Pyle happened across the benfits of deep stops because of his itchy thingy .................... ictheology :). I think that after deep dives he molests his fish samples with a pointy thing to relieve the pressure in their swim bladders and he noticed he felt better after dives with these fishy stops than he did after no such stops.
 

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Diving happy
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thumbs up from me as well on Pyle stops. On the rare occasions I actually go deepish (that is deepish for me!) then I do them. And without a bladder syringe..
 

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A short fat well off crap cave diver. Likes wrecks
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1: deep stops are predominatly a way of deeling with helium in the mix

2: deep stops INCREASE the decompresion comitment

3: Too many deep stops and too slow an ascent is a bad thing


Bhulman deco was designed arround air. the move over to trimix didnt realy get the same reserch and developmnet. As a result helium was dealt with as just a load more nitrogen.

RIchard Pyle incorporated deep stops on his dives in the 60-120m zone and found improvements in himself and in the specimins he was recovering. This was obviously on Trimix.

Deep stops have been formalised by the use of Gradient factor deco. Using a low initial gradient (like 10 or 20) introduces a lot of deep stops to the dive. However it also adds a lot of deco to the overall run time.


So why would we do it?

Because it is easier on our bodies and we feel better after the dive.


Is it necessary on air or Nitrox depth dives?

Probably not.

Recent reserch found that too many deep stops were not benificial on nitrox dives.

ATB

Mark
 

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Nigel Hewitt
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I started with Pyle stops, dabbled with Gradient Factors and now just do slow ascents and watch the VR3's deep stops vanish before I get there.
 

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ccr_ada top DAC guru 001#Blackberry pin 283E29BB
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3: Too many deep stops and too slow an ascent is a bad thing
you do spout some crap :tongue:
it just adds to the total deco time not bad if the is something to see and do
as long as you have the gas and scrubber is ok!


ada:popcorn:
 

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A short fat well off crap cave diver. Likes wrecks
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you do spout some crap :tongue:
it just adds to the total deco time not bad if the is something to see and do
as long as you have the gas and scrubber is ok!


ada:popcorn:

Actualy this was the findings of a 2007 panal of the worlds leading experts on decompresion theory, but you never know, it could just be crap.

ATB

Mark


EMPIRICAL EVALUATION OF THE EFFICACY OF DEEP STOPS IN AIR DECOMPRESSION DIVES



Gerth WA, Gault KA, Doolette DJ



Navy Experimental Diving Unit, Panama City, FL



BACKGROUND: Classical decompression algorithms limit hypothetical tissue gas contents and prescribe decompressions that advance rapidly to shallow stops where most of the total stop time (TST) is scheduled. Recent bubble-based algorithms limit calculated bubble profusion and size and prescribe decompressions with TST skewed toward deeper stops. Navy Experimental Diving Unit (NEDU) has completed a controlled comparative study of these approaches.



MATERIALS AND METHODS: Divers wearing swimsuits and t-shirts, breathing surface-supplied air via full face masks, and immersed in 86 OF water in the NEDU Ocean Simulation Facility wetpot were compressed at 60 fsw/min to 170 fsw. They performed 115 Watt cycle ergometer work during an ensuing 27.2 minutes at bottom and were decompressed at 30 fsw/min with stops prescribed by one of two schedules, each with 174 min TST. Schedule 1, with first stop at 40 fsw, was prescribed by the man-tested, deterministic gas content, WALl8 Thalmann Algorithm. Schedule 2, with first stop at 70 fsw, was the optimum distribution of TST according to the manndive 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-Iow 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). On review, one Schedule 2 DCS was excluded, but the result remained significant (p=0.047). Most DCS was mild, late onset, Type I, but two Schedule 2 cases involved rapidly progressing CNS manifestations.



CONCLUSIONS: The deep stops schedule had a greater risk of DCS than the matched conventional schedule. Slower gas washout or continued gas uptake offset benefits of reduced bubble growth at deep stops.

UHMS ASM . 2007
Session A

A4 (President's Competition) Oral Presentation: 0939 - 0951 Poster Presentation: 1045 - 1200



DIFFERENCE IN BUBBLE FORMATION USING DEEP STOPS IS DEPENDENT ON LENGTH OF BOTTOM TIME; EXPERIMENTAL FINDINGS AND THEORETICAL SUPPORT



Gutvik CR, M0l1erh:Jkken A, Brubakk AO



Baromedical and Environmental Physiology, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Norway



BACKGROUND: Deep decompression stops compared to more conventional shallower stops have recently been introduced. Most findings and theoretical work on excess gas phase models suggest an apparent advantage of using deeper stops. However, some reports indicate that the incidence and/or risk of decompression sickness may actually increase following such procedures.



MATERIALS AND METHODS: The impact of different decompression schedules was tested on pigs compressed in a dry chamber monitored using ultrasonic imaging. A total of 26 pigs were divided into 4 groups of 6 and one group of 2 (aborted protocol). Two groups performed a shallow/long (30 msw / 70 min) dive. One group followed a Buhlmann / Uwatec decompression procedure while the other followed a procedure generated by the Copernicus bubble model. The three last groups did a deep/short (65 msw / 20 min) dive followed by a Buhlmann decompression procedure, a Copernicus procedure (aborted profile) and a revised Copernicus procedure respectively.



RESULTS: The long/shallow dive achieved a significant decrease of vascular bubbles following the procedure with deeper initial stops (Copernicus schedule) compared to the controls (Buhlmann schedule). However, on the deep/short dive the procedure with deeper stops gave a dramatic increase of bubble formation, resulting in the protocol to be aborted after two trials. A new revised Copernicus schedule with the deepest stops removed, gave a significant decrease of vascular bubble formation.

CONCLUSIONS: A new stabilizing mechanism for bubble nuclei had to be developed in order to simulate and reproduce the findings in this study. "Traditional" bubble models will in general suggest that adding some deep stops is beneficial for decompression outcome, however this may not always be true. The presented studies suggest that deep stops are not recommended on shorter dives
 

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ccr_ada top DAC guru 001#Blackberry pin 283E29BB
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you have the bit on the pigs but you forgot the bit about the goats:teeth:
and try telling that to some cave divers:rolleyes:


ada:popcorn:
 

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Here's an article I wrote recently that gives some background.

Deep Stops

The practice of introducing ‘deep stops’ into decompression profiles has become very popular with technical divers. The principles behind the idea are quite straightforward although there are a confusing number of myths and misconceptions about the topic. In this article I will try to explain some of the ideas behind deep stops as well as looking at whether the concept has any relevance for recreation divers.

Traditional decompression models as proposed by British Scientist John Scott Haldane in 1908 and subsequent generations such as Workman and Buhlmann’s models have encouraged divers to ascend relatively quickly at the end of a dive from the maximum depth to a shallow first stop depth. Most current tables and dive computers adopt this traditional approach. This includes tables such as the PADI Recreational Dive Planner, Buhlmann tables as well most current decompression computers. This model assumes that a relatively fast ascent from depth to a much shallower depth while still keeping the pressure change below a specific maximum value will give allow the maximum amount of Nitrogen to be released, or off-gassed, from the body while at the same time preventing bubbles from forming.

This approach is based on the assumption that decompression sickness is caused by the formation of bubbles in the body. The conclusion from this is that a dive which does not result in decompression sickness cannot have caused any bubbles to form. We now know that this is not strictly true. In the 1970s Doppler bubble detection showed that in fact bubbles are commonly found in divers who have been diving well within the no-stop limits of recreational tables. This contradicts the traditional Haldane approach but it shouldn’t have been a great surprise. The body just doesn’t work in absolutes and to suggest that on one side of an arbitrary limit no bubbles are formed but as soon as that line is crossed bubbles will start to form should have set alarm bells ringing for anyone with a passing knowledge of physiology.

These bubbles are known as Silent bubbles or Asymptomatic bubbles as they do not cause any of the traditional signs and symptoms of decompression illness but can cause excessive tiredness or fatigue sometimes experienced after diving. In addition an excess of silent bubbles can cause problems for repetitive dives.

A number of ‘tweaks’ have been applied to the traditional Haldanian approach to try and reduce the formation of bubbles during otherwise uneventful dives. Most of these result in the introduction of much deeper initial stops or, for no-stop dives, the addition of additional, deeper safety stops. As a result the term ‘deep stops’ has become a generic term for stops introduced to avoid the formation of silent bubbles. The best known flavour of deep stops is the approach developed by Richard Pyle and as a result the term ‘Pyle stops’ has been used almost as commonly as deep stops.

Richard Pyle is an experienced diver and marine biologist. Specifically he is an ichthyologist, although he describes himself as a ‘fish-nerd’. Pyle regularly dives to depths of 60-100m in order to study and collect specimens of the various fish species that live at these depths. During dives to these depths Pyle noticed that after some of his dives he felt overly tired and lethargic, a classic indication of asymtomatic DCI and silent bubbles, whereas after other dives there were no such indications. He realized that the feeling was related to decompression rather than just the physical exertion of the dive as a dive to 60m for a total time of an hour would give more of a feeling of tiredness than a dive of 4-6 hours at a much shallower depth.

Pyle tried to identify the factors that separated the dives on which he felt good from the ones in which he felt overly tired. He considered a whole range of factors including obvious ones such as the length of the dive, depth, current, hydration levels, whether he had felt seasick during the journey, extra time added to the last deco stop, water temperature, how well he has slept the night before, etc as well as less obvious factors such as the clarity of the water, days or dates of the month on which the dives were carried out, etc.

After looking for patterns in the dives which produced no signs he eventually realized the common factor was that on dives on which he was catching and raising fish specimens from depth he was much less likely to get signs of asymptomatic DCI than on dives where no specimens were collected. This was a surprising result as initially there seemed to be no explanation as to why these dives would produce less symptoms. The major difference in these dives was that, in order to prevent damage to the fish from the gas in their swim-bladders expanding upon ascent, he would use a hypodermic syringe to extract air from their swim bladders during the ascent. The pause in the ascent required to carry out this procedure was usually much deeper than his first prescribed decompression stop, for example on a 60m dive, the first decompression stop would usually be around 15m, but Pyle would pause to remove air from the swim-bladder at around 40m. So, whenever he was collecting fish, his ascent profile would include an extra 2-3 minute stop much deeper than the first decompression stop required by a traditional decompression model. Using a traditional decompression model this approach doesn’t make sense as the traditional model predicts that by stopping deeper you are not off-gassing effectively in some of your tissues and are allowing additional gas loading in other tissues. A traditional model would indicate that these stops should increase the symptoms of sub clinical DCI rather than reducing them.

Despite being at odds with traditional decompression theory Pyle concluded that it was these “deep stops” which were reducing the signs of lethargy. As a result he began to include these “deep stops” in all his deep dives with a subsequent reduction in signs of sub-clinical DCI.

Through an empirical process Pyle developed the following process for calculating deep stops.
1. Find the midpoint between the max depth and the first traditional decompression stop.
2. Add a deep stop of 2-3 minutes at this mid point.
3. If the distance between the deep stop and the first traditional stop is greater than 6m then add an additional deep stop at the midpoint between the deep stop and the first traditional deco stop.
4. Repeat until there is less than 6m to the first traditional deco stop

Some versions use a difference of less than 6m between the last deep safety stop and the first required stop. This is more common for dives of less than 40m. Other versions recommend a stop of 1-2 minutes rather than 2-3 minutes. Divers using a dive computer will find that the computer will recalculate the decompression stops and, depending on the make and model of the computer, may add additional decompression time and even additional decompression stops. This can increase the overall length of the ascent as many current dive computers use a traditional algorithm which penalises the additional time spent at depth during the deep. This additional time on the total dive can be considered an additional safety margin.

Pyle deep stops – a recreational example
When carrying out a no-stop dive to 40m we will not incur any mandatory decompression, however we can consider the recommended safety stop at 5m to be the equivalent of the first decompression stop.

Take the distance between the depth when you start your ascent 40m
and the safety stop 5m
and find the mid point (40+5)/2 = 23m
This depth will be our first deep safety stop and should be 1-2 minutes in duration
If the distance between your first deep safety stop and your safety stop 23-5 = 18m
Is greater than 6m Yes it is
then add an additional deep safety stop at the midpoint between the first deep safety stop 23m
and the safety stop 5m
Which is (23+5)/2 = 14m
If the distance between your latest deep safety stop and your safety stop 14-5 = 9m
Is greater than 6m Yes it is
then add an additional deep safety stop at the midpoint between the first deep safety stop 14m
and the first required decompression stop. 5m
Which is
(14+5)/2 = 9m
(rounded up to 15m)
If the distance between your latest deep safety stop and your first required stop 9-4 = 4m
Is not greater than 6m No it isn’t
Then carry on to first traditional safety stop

So in this example we would end up with Pyle stops at 23m, 14m, 9m as well as a traditional safety stop at 5m.

Pyle met considerable skepticism when he initially discussed his approach. This is not surprising as his findings directly contradicted established decompression theory. However later decompression research into ‘bubble models’ calls for initial decompression stops that are much deeper than those suggested by traditional neo-Haldanian decompression models. Although calculated in completely different ways they were very similar to the deep stops generated by Pyle’s empirically derived method. This gave credence to the empirically derived method derived by Pyle. As the decompression modeling community as well as the growing ranks of technical divers began to appreciate the implications of ‘Bubble models’ Pyle’s empirical approach began to be acknowledged as having some scientific basis. Although an over-simplification in some cases it certainly provided the easiest way to incorporate deep stops in decompression practice and “Pyle Stops” has become a commonly used term.

In order to investigate the claimed benefits of deep stops DAN performed a series of dives to study the impact of ascent rates and deep stops on bubble formation. A series of dives were carried out to 25m for 25 minutes followed, after a surface interval of 3 hours and 30 minutes, by another dive to 25m for 20 minutes. Ascent rates of 18m, 10m and 3m were performed on each of the dives. Each ascent rate was combined with a direct ascent to the surface, a traditional safety stop of 5 minutes at 6m and finally a deep stop of 5 minutes at 15m combined with a traditional safety stop of 5 minutes at 6m. The only exception was that a direct ascent was not performed with an 18m/minute ascent rate as this was considered too risky. After each dive Doppler bubble detection was used to calculate a Bubble Score Index (BSI) which indicates the number of bubbles formed during that dive. The results of the research are shown in Table 1.

If we just look at the results for the BSI, as shown in Figure 2, we can see that the bubble score for the ascents with no stops was higher then than with a stop or 6m or a stop at 15m and 6m. The results for the ascents incorporating a deep stop at 15m as well as a stop at 6m clearly show a significantly lower BSI. This seems to confirm that the incorporation of a deep stop has a positive effect on bubble formation, even on recreational no-stop dives in the 25m depth range.

From the graph we can also see that an ascent rate of 18m/min gives a higher bubble score (where carried out) than the 10m/min. Interestingly we can also see that the 3m/minute ascent rate gives a higher bubble score reading than either the 18m/minute or 10m/minute ascents. This shows that a slow ascent rate is beneficial but that there is such a thing as an ascent rate that is too slow. The best combination is a 10m/minute ascent rate combined with a deep stop at 15m and a traditional safety stop at 6m.

There has been a recent study by the US Navy which appeared to show the opposite conclusion to the DAN study in terms of the benefit of deep stops. This received a lot of publicity and was seen by many as evidence that deep stops were not such a good thing. However, if you look at the US Navy study you can see that they are testing something very different to what we have been calling deep stops and so their conclusions do not apply to this discussion.

The value of deep stops has been increasingly recognized in the recreational diving area. It would appear that deep stops can give an advantage when performing repetitive dives over multiple days, typical on a recreational diving holiday. A number of the most popular manufacturers of dive computers have recently introduced models that include some form of deep stop or micro bubble suppression algorithm and the Sub Aqua Association has recently introduced a set of deep stop tables designed for recreational club diving. The inclusion of additional safety stops on recreational dives is likely to be more widely adopted in the future in an attempt to provide an additional safety margin and as a way of reducing post dive fatigue.

For more information on deep stops and other aspects of decompression the following are recommended.
Powell, M. J. 2008. Deco for Divers. Aquapress
Baker, E.C. 1998. Clearing up the confusion about deep stops. Immersed. Vol. 3, No. 4, 23-31.
Marroni A, Bennett P.B, Cronje F.J, Cali-Corleo R, Germonpre P, Pieri M, Bonucelli C, Balestra C. “A deep stop during decompression from 82 fsw (25m) significantly reduces bubbles and fast tissue gas tension” Undersea and Hyperbaric Medicine Journal, Volume 31 No 2.(2004)
Pyle, RL. The importance of Deep Safety Stops: Rethinking Ascent Patterns From Decompression Dives. Deep Tech, Issue 5

For more information on any aspect of technical diving then contact Mark on
Web: Dive-Tech: TDI and BSAC Nitrox, trimix and technical diver training courses with instructor Mark Powell
Email: [email protected]
Phone: 07770 864327
 

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A short fat well off crap cave diver. Likes wrecks
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Hi Mark

Before we get too technical on this, in your opinion would it be fair to say that there is far less of a need for deep stops on shallow dives (less than 30m) than on deep dives? Would you agree that a 23m stop on a 40m air dive dive for 17mins (which equates to a 5min stop at 6 running Buhlman) is unnecessary. Id do a normal ascent to 12 and then 3m/min to 6.

However if i were to do the same 40m dive on a CCR with 18/45 diluent Id start my deep stops deeper and do 1min every 3m (a 3m/min ascent) from 21m.

This is because of the Helium in the mix.


Like most divers i did a lot of shallow diving before I learned what deco really was. NDLs on PADI tables and computer dives on Suunto's and Marres computers. All of which pretty much involved an immediate ascent to 9 or 6m followed by a stop and an immediate ascent from 6m.

Thats the sort of dive profile millions of divers do every day and very very few get bent.

Richard Pyle never found his Buhlman deco or ascents an issue on shallow dives, he found his problem between 60 and 100m on dives lasting a couple of hours or more and running a very high helium mix .

Reading between the lines of GUEs latest thoughts on deco, they have altered their ratio deco profiles to shorten the deep stops and they have great emphasis on the 10m ascent rate that most of us find scary fast. It would appear that the intermediate ascent as been cut short as well so it looks like the greatest exponents of deep stops are themselves looking to cut back on the amount of time spent decoing at depth?


I have no idea who's got it right but i do know that i never got bent on several hundred dives between 10 and 40m blindly following a Marres Surveyor or a Suunto.

I also know that since i started doing deep diving there have been a lot of ideas and fads. Pyle stops came to my attention is 2003 or 4 not that long ago. There was the get of the trimix ASAP idea there was the very rapid ascent to first stop idea. Staggered gas swapping was another. RGBM was the cure for all deco than quickly condemned. VPM was the new RGBM and that quickly became VPMB with VPMBE for very deep dives and this is currently being condemned by a lot of regular deep divers. It would appear now that GF deco is the way forward for most but there are still some big name divers playing with VPM.


All in all it become apparent to me in the last ten years that there is no single true path to the right deco profile.

I have nothing against deep stops but divers should be made aware that slow ascents and deep stops should result in MORE shallow deco. Whilst such ascents may reduce the physical strain of the ascent its obvious that on gassing will be occurring as well and that needs to be dealt with on the shallow stops.

Sunnto divers wont have a problem because the computer will automatically add the deco penalty for the deep stops, however someone adding deep stops to a fixed Buhlman table like the PADI table should be padding the shallow stop in order to compensate.

Don't be fooled by the soft image of PADI. The RDP table is fairly aggressive compared to a dive planned on a typically conservative 20/80GF program.

ATB

Mark
 

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Before we get too technical on this, in your opinion would it be fair to say that there is far less of a need for deep stops on shallow dives (less than 30m) than on deep dives?
I would say there was 'less' need but certainly not 'far less'.
Would you agree that a 23m stop on a 40m air dive dive for 17mins (which equates to a 5min stop at 6 running Buhlman) is unnecessary.
No wouldn't agree. 30-40m is where it gets interesting. Im increasingly starting to think that anything more than a 20m ascent off the bottom and to the first stop needs some kind of deep stop.

However if i were to do the same 40m dive on a CCR with 18/45 diluent Id start my deep stops deeper and do 1min every 3m (a 3m/min ascent) from 21m.

This is because of the Helium in the mix.
Interesting, what specific factors with regard to Helium cause you to change the approach?


Thats the sort of dive profile millions of divers do every day and very very few get bent.
I think millions use these tables for NDL diving but far fewer use them for deco diving.

All in all it become apparent to me in the last ten years that there is no single true path to the right deco profile.
Absolutely, the more I learn about deco the more I realise that there are great big unanswered questions.
 

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A short fat well off crap cave diver. Likes wrecks
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I would say there was 'less' need but certainly not 'far less'.

No wouldn't agree. 30-40m is where it gets interesting. Im increasingly starting to think that anything more than a 20m ascent off the bottom and to the first stop needs some kind of deep stop.
Rightly or wrongly I use a totaly different profile with nitrox dives than i do with trimix dives. A Nitrox dive to 40m would be a 30/90 GF profile where as a Trimix dive would be 10/90. This is the result of my own empirical data which obviously only relates to me.

As a result a 30/90 dive to 40m for 17mins on say 25% nitrox would be

1 @ 15
1 @ 12
1 @ 9
6 @ 6

Basically a 3m/min ascent from 15m to 6 then an actual stop at 6.


The same dive on OC trimix is a little difficult to compair as the mix screws it for a single gas dive but on say 25/35 trimix

1 @ 15
1 @ 12
1 @ 9
11 @ 6

However i found out by chance in my early days of mix diving that a different approach worked better. Andyp became my buddy and he was running 20/85 profiles which added another more deep stops and extended the shallow stops and I felt better post dive.

Obviously this wasn't on 17mins at 40 this was on 35-50 mins at 45-60m diving which is what we did most of the time.

In the good old deep air days I dint find a problem running 30/90. I did multiple dives days reverse profiles and loads of stuff i shouldn't but i felt fine with my 30/90s I really only started to notice the tiredness headaches and feelings of being kicked around the boat, when I switched to trimix.

Things got interesting when I purchased a VR3 in 2002. I found my TTS figures were wrong and it made me realize that I had been running deco on depth and stop time rather than run time and id been doing it wrong.

In vogue at that time was ascent rates of around 5m/min from the deep stop. The VR3 Pyle type stops were very deep and i quickly discovered that my slow ascent rates were racking up time on the shallow stops. This made me look at the effects of ascent rates and deep stops on Decoplanner and sure enough i discovered that my ultra slow ascents and deep deep stops were adding to my shallow stop time.

So my understanding of the impact of slow ascents and deep stops all came about by accident.

I started to do research in earnest and i was particularly attracted to GI3s work especially his comments on Helium improving deco and his famous "If you get the deep stops right the shallow stops don't matter" comments matched with his rather drastic slashing of the shallow stop times.

This seemed to fit in with the emerging VPMB profiles and I started to play with them. Some of the profiles were comming in around 10/125GF by comparison of the last 5 stops

End result was feeling totaly crap and a trip to the pot for a suspected but unconfirmed bend.

I gave up on these profiles but I left the deep stops in but i started to speed up ascent rates closer to 10m/min and pad out the shallow stops again

After about four years and 300ish deco dives I found what worked for me. 10/90GF on Trimix dives and 30/90 on nitrox dives.


I also gave up on the VR3 and switched to a GF computer (Hammer Head) I quickly found running 10/90GF I was doing my deep stop a lot shallower than the VR3.

I notice now when diving alone or with similar buddies that if I motor on up to my deep stops ASAP I feel better after the dive. Diving with VR3 buddies i have to fudge my deep section and this doesn't leave me feeling as clean afterwords.

So based on my own research and a fair chunk of diving in the 50-80m zone I have concluded slow ascents and very deep stops are not helping me. I don't mind how long I stay in the water and I am not in the group who seem to constantly want to reduce deco. I just want to do the minimum possible damage to my self. If feeling good is an indication of this then I have to say I am no longer a fan of the slow ascent and deep stop camp.


Interesting, what specific factors with regard to Helium cause you to change the approach?

Being bent whilst still in the water is a good indication that Helium needs to be treated differently. Thats something i have witnessed twice and experienced my self once. Always on over rich dives. I got hit diving 15/60 on a 55m dive CCR and Pete was diving OC mix for 70 on a 60m dive.

Helium is far less tolerant of errors during the ascent than Nitrogen. We all know this basic rule and it suggest to me that we need to be reducing the He in our bodies to a minimum deep to increase the margin for error in the shallows.

For reasons which i do not understand it would appear that forcing the pressure gradient and bubble radius on Helium just doesn't work as well as it does with nitrogen.


I think millions use these tables for NDL diving but far fewer use them for deco diving.

But you offered up a dive with just a safety stop as an example? So isnt this a NDL dive?

My point is this, PLANNING a GF dive on deco software running a low/high GF is fine as the computer will cope with the addition of the deep stops. However getting out the BSAC88s or RDPs and adding arbitrary deep stops to those profiles is not improving the safety of the dive.

I don't believe Mr Pyle sets a good example. His addition of the deep stops to conventional decompression profiles makes no allowance on the shallow stops. Perhaps this is proof i am wrong but Id suggest that his warm water deco may be the thing thats allowing this to work.


Absolutely, the more I learn about deco the more I realize that there are great big unanswered questions.

Likewise and I am only putting up my comments as a caveat to those thinking of trying new stuff. I read all the articles books and attended the talks but in the end it was what happened in the water that formed my opinions today.

If new advances in decompression science happen Ill no doubt give them a go too.

Now where did I put those Aspirin I am off diving tomorow :D

ATB

Mark
 
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Technical Drinking International -Cidrox Instructo
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Would you trust a decompression theory from someone who does 110m technical dives wearing just a pair of shorts and a short sleeve short ? The guys nuts.
 

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Finless: You couldn't invent him...
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Would you trust a decompression theory from someone who does 110m technical dives wearing just a pair of shorts and a short sleeve short ? The guy's nuts.
I prefer to think of him as "experienced". Also, given his youthful stupidity that got him bent in a major way I think lends more weight to his experiences.
 

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Would you trust a decompression theory from someone who does 110m technical dives wearing just a pair of shorts and a short sleeve short ? The guys nuts.
I did smile - I think he's great - a real character :D
 

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Creature of the night
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14,183 Posts
Would you trust a decompression theory from someone who does 110m technical dives wearing just a pair of shorts and a short sleeve short ? The guys nuts.
Clothes don't maketh the man.........or diver ;)

Safe diving,
Steve

P.S. Chasey, we need a graph about now mate? :kiss:
 

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TDI Advanced Trimix Instructor
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646 Posts
Hi

Are these two the same thing?

Is the case for Deep Stops now acceptably proven? As far as anything is in this theory driven sport. Can anyone point me at comparison material please that should give confidence for adopting them.
Rgds
Wibble

With Helium rich mizes it seems that deep stops help a million because helium ongasses and off gasses very fast.
With air, till now, the benifit of deep stops has not really been proven or disproven.

It would be fair to say, that "deep stops" really have no definition, while Pyle stops do have a fixed technique.

Some agencies have standard ways of calculating deep stops, while some manufacturures makes their own only to bewilder customers.
A very tricky subject actually.
 

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Registered
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379 Posts
Discussion Starter #20
Thank you

All and Particularly Mark

Thank you for the fulsome answers. I am a recreational diver with a max bottom of 40m. On a recent trip an Instructor who is also a commercial diver was asking why, as I had a VYTEC DS was I not using Deep Stops? I explained that it was difficult to find buddies who had the same algorithim and that to get a buddy up to speed on why I was stopping and possibly loading their schedule was sometimes hard to do. However I also explained that I thought that from a DAN study DS was as yet unproven. Guess I was wrong.
However I guess the new questions are does the team think,
a) that DS is good for a recreational diver who sometimes dives 30-40m.
b) that DS is good for a recreational diver on Nitrox mixes in the zone to 37m. Where the emphasis is on bottom time, not Air profile.

Thank you very much again.
Rgds
Wibble
 
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