Deep Stops Increases DCS

[rossh]

Well, there is the photomicrograph of exactly that happening in post 1002 of this thread. Besides which it would be a bit silly to presume that those VGE which originate from extravascular tissue are those bubbles which formed furthest from the capillaries.

I only ask to illustrate the fallacy in your argument, but can you show us some science that clearly disproves a connection between extravascular and intravascular bubbles?

... All of which is photos of severe injury..... The new rabbit test is severe injury..... Of course its choc-o-block full of bubbles - what else would one expect to see on a severe profile abuse? Ruptures and bubbles everywhere, but that says nothing about non injured normal people on normal dives.

What no-stop time for 100 fsw are you presuming for a 20kg pig that performs a 45 minute oxygen prebreathe before descent and is anesthetized at depth? Hint: DCS susceptibility increases with body mass, oxygen prebreathe decrease decompression obligation, and work at depth increases decompression obligation.

Using the "Simon Mitchell" approved deco method, these poor little pigs missed out 225 mins of deco time.
Using real deco calculations they missed 130 mins of ZHL-C deco time, or 139 mins of VPM-B deco time.

All that includes a 90 min pre-breath of O2.


added: oops, I used 90 min pre-breath in the chart, instead of the 45 in the test. That would make the deco even longer.

The animals with low VGE had few or no tissue bubbles.

Simon M

I have to say - that's really... . Do you really expect that these no VGE rabbits, after skipping 489 minutes of "approved deco", they where some how still healthy? Of course not.

******

Here is a suggestion. Get a new batch of rabbits - send em on a dive, decompress them normally without injury - separate them into Hi/Lo VGE, terminate them, and work out the what heck is causing different VGE outcomes.

Then, and only then, will we be able to move forward. Because right now - we have no clue as to why such an enormous difference in VGE exists You keep pointing at VGE as some litmus test, when all of the expert opinion says do not do that. It meaningless hot air until you can identify why VGE is so varied between subjects.

..

.

 

[rossh]

Hi.

I've really been avoiding this thread.

In January I did a long run in Cathedral. My dive buddy and I had a 200 minute bottom time at an average depth of 150'. I've been told by my dive buddies that I frequently run an aggressive deco, and on this dive there I did nothing different.

My partner on the dive was running VPM-B/E on +3 on a popular DC. When we got to our oxygen stop his computer claimed he had about 40 minutes less deco than me (I was running my standard "aggressive" deco).

On all of our other dives, he usually did more deco than me, so he decided to stay with me.

I'm not a decompression scientist, but my experience has been that on longer dives VPM produces significantly shorter shallow stops -- it seems to forget that the time I'm spending deeper I'm still on-gassing in my slow tissues. While it may work fine for short "bounce" dives, it really seems to get wonky when the dives are getting longer.

One of my dive buddies and I are planning a 300 minute bottom time at Cathedral within the next two months (anticipated run-time of about 10 hours), and I will not be trusting my body to VPM for that.

In my opinion, the best algorithm is the one that gets me out of the water without getting twisted, and I really have zero interest in hurting myself due to a faulty algorithm. Although ZHL16+GF's may not be the best thing in the world either, they're working for the dives my friends and I are doing, where VPM clearly doesn't.

Ross, Multi-Deco is a nifty piece of code, but I am struggling with recommending it to my students given your religious fanaticism for VPM. I have an AN/DP class coming up in two weeks and I'm currently evaluating a few other dive planning tools because of your constant proselytizing for VPM. You could have simply taken the high road and said "my tools support the common and popular decompression algorithms and you should make an educated decision on which model suits your diving" and been a winner.

MultiDeco 4.07 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 40/85

Dec to 150ft (2) Diluent 20/30 1.00 SetPoint, 60ft/min descent.
Level 150ft 197:30 (200) Diluent 20/30 1.00 (1.11), 86ft ead, 94ft end
Asc to 120ft (201) Diluent 20/30 1.00 SetPoint, -30ft/min ascent.
Asc to 100ft (201) Diluent 32 1.30 SetPoint, -30ft/min ascent.
Stop at 100ft 1:20 (203) Diluent 32 1.30 SetPoint, 82ft ead
Stop at 90ft 5:00 (208) Diluent 32 1.30 SetPoint, 69ft ead
Stop at 80ft 8:00 (216) Diluent 32 1.30 SetPoint, 56ft ead
Stop at 70ft 10:00 (226) Diluent 32 1.30 SetPoint, 44ft ead
Stop at 60ft 15:00 (241) Diluent 32 1.30 SetPoint, 31ft ead
Stop at 50ft 20:00 (261) Diluent 32 1.30 SetPoint, 18ft ead
Stop at 40ft 28:00 (289) Diluent 32 1.30 SetPoint, 6ft ead
Stop at 30ft 39:00 (328) Diluent 32 1.30 SetPoint, 0ft ead
Stop at 20ft 52:00 (380) Oxygen 1.30 (1.60), 0ft ead
Stop at 10ft 102:00 (482) Oxygen 1.30 (1.30), 0ft ead
Surface (482) Oxygen -30ft/min ascent.

MultiDeco 4.07 by Ross Hemingway,
VPM code by Erik C. Baker.

Decompression model: VPM - B/E

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 3

Dec to 150ft (2) Diluent 20/30 1.00 SetPoint, 60ft/min descent.
Level 150ft 197:30 (200) Diluent 20/30 1.00 (1.11), 86ft ead, 94ft end
Asc to 120ft (201) Diluent 20/30 1.00 SetPoint, -30ft/min ascent.
Asc to 100ft (201) Diluent 32 1.30 SetPoint, -30ft/min ascent.
Stop at 100ft 0:20 (202) Diluent 32 1.30 SetPoint, 82ft ead
Stop at 90ft 3:00 (205) Diluent 32 1.30 SetPoint, 69ft ead
Stop at 80ft 6:00 (211) Diluent 32 1.30 SetPoint, 56ft ead
Stop at 70ft 9:00 (220) Diluent 32 1.30 SetPoint, 44ft ead
Stop at 60ft 12:00 (232) Diluent 32 1.30 SetPoint, 31ft ead
Stop at 50ft 18:00 (250) Diluent 32 1.30 SetPoint, 18ft ead
Stop at 40ft 25:00 (275) Diluent 32 1.30 SetPoint, 6ft ead
Stop at 30ft 34:00 (309) Diluent 32 1.30 SetPoint, 0ft ead
Stop at 20ft 48:00 (357) Oxygen 1.30 (1.60), 0ft ead
Stop at 10ft 89:00 (446) Oxygen 1.30 (1.30), 0ft ead
Surface (446) Oxygen -30ft/min ascent.

Thanks for you input.

Yes, by all means, on a big dive, take all the precautions you want - no need to test anything. Safety is paramount on the unknowns like this

You are highlighting a 10% difference in deco time - not much at all really. But its also a GF plan way beyond its intended use and calibration, and GF has an expotential growth errror, so that make the GF plan a little bigger than it needs.

Did you know where VPM-B/E came from? It was David Shaw (RIP), who did a 270m dive on VPM-B, with some extra time added. We modeled his changes and that is what VPM-B/E is.

************

Yes, your correct "my tools support the common and popular decompression algorithms and you should make an educated decision on which model suits your diving"

But we also cannot let good existing models get ruined by over inflated sham attacks.

*******
Added,

If you dial VPM-B/E up to +5, you will get a plan that exactly the same as the GF version above.

Decompression model: VPM - B/E

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 5

Dec to 150ft (2) Diluent 20/30 0.70 SetPoint, 60ft/min descent.
Level 150ft 197:30 (200) Diluent 20/30 1.00 (1.11), 86ft ead, 94ft end
Asc to 100ft (202) Diluent 20/30 1.00 SetPoint, -21ft/min ascent.
Stop at 100ft 1:37 (204) Diluent 32 1.30 SetPoint, 82ft ead
Stop at 90ft 4:00 (208) Diluent 32 1.30 SetPoint, 69ft ead
Stop at 80ft 7:00 (215) Diluent 32 1.30 SetPoint, 56ft ead
Stop at 70ft 10:00 (225) Diluent 32 1.30 SetPoint, 44ft ead
Stop at 60ft 14:00 (239) Diluent 32 1.30 SetPoint, 31ft ead
Stop at 50ft 20:00 (259) Diluent 32 1.30 SetPoint, 18ft ead
Stop at 40ft 27:00 (286) Diluent 32 1.30 SetPoint, 6ft ead
Stop at 30ft 40:00 (326) Diluent 32 1.30 SetPoint, 0ft ead
Stop at 20ft 53:00 (379) Oxygen 1.60 ppO2, 0ft ead
Stop at 10ft 103:00 (482) Oxygen 1.30 ppO2, 0ft ead
Surface (482) Oxygen -20ft/min ascent.

 

[PfcAJ]

Thanks for you input.

Yes, by all means, on a big dive, take all the precautions you want - no need to test anything. Safety is paramount on the unknowns like this

You are highlighting a 10% difference in deco time - not much at all really. But its also a GF plan way beyond its intended use and calibration, and GF has an expotential growth errror, so that make the GF plan a little bigger than it needs.

Did you know where VPM-B/E came from? It was David Shaw (RIP), who did a 270m dive on VPM-B, with some extra time added. We modeled his changes and that is what VPM-B/E is.

************

Yes, your correct "my tools support the common and popular decompression algorithms and you should make an educated decision on which model suits your diving"

But we also cannot let good existing models get ruined by over inflated sham attacks.

You're so far in over your head, Ross.

 

[David Doolette]

What no-stop time for 100 fsw are you presuming for a 20kg pig that performs a 45 minute oxygen prebreathe before descent and is anesthetized at depth? Hint: DCS susceptibility increases with body mass, oxygen prebreathe decrease decompression obligation, and work at depth increases decompression obligation.

Using the "Simon Mitchell" approved deco method, these poor little pigs missed out 225 mins of deco time.
Using real deco calculations they missed 130 mins of ZHL-C deco time, or 139 mins of VPM-B deco time.
.

If they were humans performing some work on the bottom, but they were 20kg anaesthetized pigs. The dive was enough to to give some of them DCS, but what do you think the no-stop time should have been?

 

[huwporter]

The kindest explanation I can think of is that Ross has decided for some reason to discredit VPM from the inside.

 

[rossh]

If they were humans performing some work on the bottom, but they were 20kg anaesthetized pigs. The dive was enough to to give some of them DCS, but what do you think the no-stop time should have been?

I don't have a ZHL-PORK or VPM-PORK planning tool. Why don't you tell us there David?

 

[Dr Simon Mitchell]

Ross, you are demonstrating a remarkable degree of naivety about animal models of DCS. David is trying to tell you that you can't interpret them in terms of human decompression tolerance. He is an expert. Why don't you listen to him?

I have to say - that's really... . Do you really expect that these no VGE rabbits, after skipping 489 minutes of "approved deco", they where some how still healthy? Of course not.

Read the paper. That is exactly what the results say. Despite what you consider to be a catastrophic decompression a substantial proportion of the rabbits had low VGE including 2/14 with NO VGE. The decompression imposed on these animals produced a good even spread of VGE. You could have exposed them to a human style dive and probably none of them would have produced VGE. What use would that have been when you are trying to correlate different levels of VGE against tissue bubbles?

You have constantly deprecated the importance of VGE on the basis of your claim that they do not reflect bubbling in the tissues. You have repeatedly asked for proof of a correlation between VGE and tissue bubbles. That is exactly what this newly published study provides. Animals with no or low VGE had no or low tissue bubbles. Animals with high VGE had high tissue bubbles. I'm sorry if this really upsets you, but maybe you should have listened to the advice given to you on this matter hundreds of posts ago.

But we also cannot let good existing models get ruined by over inflated sham attacks.

You have got it completely around the wrong way Ross. The reason virtually all of these dive forum debates have taken place is because of attacks on the modern decompression research literature by you.

Simon M

 

[David Doolette]

I don't have a ZHL-PORK or VPM-PORK planning tool. Why don't you tell us there David?

So you cannot comment authoritatively on the decompression requirements of 20 kg anaesthetized pigs. So how can you make the the following statement dismissing the relevance of the Swan et al. study to everyday diving?

The Swan study: they used pigs, but if they used humans, they skipped 2 1/2 hours of deco time..... So are those big bubbles truly representative of the tiny / almost non existent harmless ones we get in everyday diving? Probably not. Of course when one blows up the deco so grossly, everything appears at the same time.
>

 

[shoredivr]

It's like some kind of shadow play Ross is involved in.

If it didn't involve actual diving injuries it might even be macabrely amusing.

 

[UWSojourner]

Hi.

I've really been avoiding this thread.

In January I did a long run in Cathedral. My dive buddy and I had a 200 minute bottom time at an average depth of 150'. I've been told by my dive buddies that I frequently run an aggressive deco, and on this dive there I did nothing different.

My partner on the dive was running VPM-B/E on +3 on a popular DC. When we got to our oxygen stop his computer claimed he had about 40 minutes less deco than me (I was running my standard "aggressive" deco).

On all of our other dives, he usually did more deco than me, so he decided to stay with me.

I'm not a decompression scientist, but my experience has been that on longer dives VPM produces significantly shorter shallow stops -- it seems to forget that the time I'm spending deeper I'm still on-gassing in my slow tissues. While it may work fine for short "bounce" dives, it really seems to get wonky when the dives are getting longer.

One of my dive buddies and I are planning a 300 minute bottom time at Cathedral within the next two months (anticipated run-time of about 10 hours), and I will not be trusting my body to VPM for that.

In my opinion, the best algorithm is the one that gets me out of the water without getting twisted, and I really have zero interest in hurting myself due to a faulty algorithm. Although ZHL16+GF's may not be the best thing in the world either, they're working for the dives my friends and I are doing, where VPM clearly doesn't.

Ross, Multi-Deco is a nifty piece of code, but I am struggling with recommending it to my students given your religious fanaticism for VPM. I have an AN/DP class coming up in two weeks and I'm currently evaluating a few other dive planning tools because of your constant proselytizing for VPM. You could have simply taken the high road and said "my tools support the common and popular decompression algorithms and you should make an educated decision on which model suits your diving" and been a winner.

MultiDeco 4.07 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 40/85

Dec to 150ft (2) Diluent 20/30 1.00 SetPoint, 60ft/min descent.
Level 150ft 197:30 (200) Diluent 20/30 1.00 (1.11), 86ft ead, 94ft end
Asc to 120ft (201) Diluent 20/30 1.00 SetPoint, -30ft/min ascent.
Asc to 100ft (201) Diluent 32 1.30 SetPoint, -30ft/min ascent.
Stop at 100ft 1:20 (203) Diluent 32 1.30 SetPoint, 82ft ead
Stop at 90ft 5:00 (208) Diluent 32 1.30 SetPoint, 69ft ead
Stop at 80ft 8:00 (216) Diluent 32 1.30 SetPoint, 56ft ead
Stop at 70ft 10:00 (226) Diluent 32 1.30 SetPoint, 44ft ead
Stop at 60ft 15:00 (241) Diluent 32 1.30 SetPoint, 31ft ead
Stop at 50ft 20:00 (261) Diluent 32 1.30 SetPoint, 18ft ead
Stop at 40ft 28:00 (289) Diluent 32 1.30 SetPoint, 6ft ead
Stop at 30ft 39:00 (328) Diluent 32 1.30 SetPoint, 0ft ead
Stop at 20ft 52:00 (380) Oxygen 1.30 (1.60), 0ft ead
Stop at 10ft 102:00 (482) Oxygen 1.30 (1.30), 0ft ead
Surface (482) Oxygen -30ft/min ascent.

MultiDeco 4.07 by Ross Hemingway,
VPM code by Erik C. Baker.

Decompression model: VPM - B/E

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 3

Dec to 150ft (2) Diluent 20/30 1.00 SetPoint, 60ft/min descent.
Level 150ft 197:30 (200) Diluent 20/30 1.00 (1.11), 86ft ead, 94ft end
Asc to 120ft (201) Diluent 20/30 1.00 SetPoint, -30ft/min ascent.
Asc to 100ft (201) Diluent 32 1.30 SetPoint, -30ft/min ascent.
Stop at 100ft 0:20 (202) Diluent 32 1.30 SetPoint, 82ft ead
Stop at 90ft 3:00 (205) Diluent 32 1.30 SetPoint, 69ft ead
Stop at 80ft 6:00 (211) Diluent 32 1.30 SetPoint, 56ft ead
Stop at 70ft 9:00 (220) Diluent 32 1.30 SetPoint, 44ft ead
Stop at 60ft 12:00 (232) Diluent 32 1.30 SetPoint, 31ft ead
Stop at 50ft 18:00 (250) Diluent 32 1.30 SetPoint, 18ft ead
Stop at 40ft 25:00 (275) Diluent 32 1.30 SetPoint, 6ft ead
Stop at 30ft 34:00 (309) Diluent 32 1.30 SetPoint, 0ft ead
Stop at 20ft 48:00 (357) Oxygen 1.30 (1.60), 0ft ead
Stop at 10ft 89:00 (446) Oxygen 1.30 (1.30), 0ft ead
Surface (446) Oxygen -30ft/min ascent.

Thanks for you input.

Yes, by all means, on a big dive, take all the precautions you want - no need to test anything. Safety is paramount on the unknowns like this

You are highlighting a 10% difference in deco time - not much at all really. But its also a GF plan way beyond its intended use and calibration, and GF has an expotential growth errror, so that make the GF plan a little bigger than it needs.

Did you know where VPM-B/E came from? It was David Shaw (RIP), who did a 270m dive on VPM-B, with some extra time added. We modeled his changes and that is what VPM-B/E is.

************

Yes, your correct "my tools support the common and popular decompression algorithms and you should make an educated decision on which model suits your diving"

But we also cannot let good existing models get ruined by over inflated sham attacks.

*******
Added,

If you dial VPM-B/E up to +5, you will get a plan that exactly the same as the GF version above.

Decompression model: VPM - B/E

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 5

Dec to 150ft (2) Diluent 20/30 0.70 SetPoint, 60ft/min descent.
Level 150ft 197:30 (200) Diluent 20/30 1.00 (1.11), 86ft ead, 94ft end
Asc to 100ft (202) Diluent 20/30 1.00 SetPoint, -21ft/min ascent.
Stop at 100ft 1:37 (204) Diluent 32 1.30 SetPoint, 82ft ead
Stop at 90ft 4:00 (208) Diluent 32 1.30 SetPoint, 69ft ead
Stop at 80ft 7:00 (215) Diluent 32 1.30 SetPoint, 56ft ead
Stop at 70ft 10:00 (225) Diluent 32 1.30 SetPoint, 44ft ead
Stop at 60ft 14:00 (239) Diluent 32 1.30 SetPoint, 31ft ead
Stop at 50ft 20:00 (259) Diluent 32 1.30 SetPoint, 18ft ead
Stop at 40ft 27:00 (286) Diluent 32 1.30 SetPoint, 6ft ead
Stop at 30ft 40:00 (326) Diluent 32 1.30 SetPoint, 0ft ead
Stop at 20ft 53:00 (379) Oxygen 1.60 ppO2, 0ft ead
Stop at 10ft 103:00 (482) Oxygen 1.30 ppO2, 0ft ead
Surface (482) Oxygen -20ft/min ascent.

I'm a little confused about what you are saying about these profiles that kensuf posted (see your comments that I bolded).

On the one hand, I thought you were saying that the GF40/85 profile was an "overinflated sham". I think you've said things like this about GF in other places so that didn't seem unusual.

But on the other hand you then matched the run time to your VPM-BE+5 profile? I don't think you're saying that your BE+5 is a "sham, etc" so can you clarify? Are both GF40/85 and BE+5 just acceptably conservative profiles that seem fine or are they both flawed because they're overinflated "shams"? Or maybe another option.