Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover

divetheworld · 25th May 2006, 09:10

Quote: (Originally Posted by Sutty)

Brent, Thanks for posting it - but where is your copy/paste from?

Neil

In case your interested, here are a couple more nice interesting articles that bring the subject up to speed.
I'm sure a few have seen these before too.

Mdemon · 25th May 2006, 09:20

Looking forward to wading through your post Brent! Looks interesting.

Mark Ellyatt et al have been harsh critics of the various deco algorythms available for a while now. Worth a quick look at his website to scare yourself silly. I particularly liked the comparison of the various algorythms, critiqued.

http://www.inspired-training.com/deco_comparisons.htm

My take is that current software is all extrapolated mathematically from the initial man-/animal-tested work. As people get hurt, so more conservatism gets thrown into the mix. The evolution of RGBM and VPM (now b,e) would seem to bear this out.

If Comex added their knowledge to the mix, even if less relevant because of the workload/support etc, this would be the first man-tested input into deco algorythms for years.

How do we feel about being guinea pigs folks? Because that's currently what we are.

jasondrake · 25th May 2006, 10:04

"ark Ellyatt et al have been harsh critics of the various deco algorythms available for a while now. Worth a quick look at his website to scare yourself silly. I particularly liked the comparison of the various algorythms, critiqued.
"

Any idea what Mark Ellyatt's using as a basis for comparison?

Ben Field · 25th May 2006, 10:19

Quote: (Originally Posted by jasondrake)

Any idea what Mark Ellyatt's using as a basis for comparison?

He uses http://www.inspired-training.com/decochek.htm

Read through the sites, sounds all well and good if abit "brash" I quote- "As you can see, the Officers don't use BUBBLE models, so why would the Troops?"

Not sure I really like the suggestion behind that but everyones entitled to their own opinion I guess...

BEN

Sue · 25th May 2006, 10:32

Quote: (Originally Posted by jasondrake)

Any idea what Mark Ellyatt's using as a basis for comparison?

This is a question/answer from an interview I've made last year to Mark Ellyatt:

Question - Decompression software for planning the dives – which one, and why?

M.E. - I like to use Decoplanner for dives up to 90metres, for deeper than this, there is nothing sufficiently reliable. I developed a program called DECOCHEK with a colleague Stephen Burton. This program analyses any dive, the diver plans the dive like normal then imports the run time into the analyzer. The program advises against inappropriate decompression stops and bad mix choices. Its very good even if I do say so myself. You can see details of it at www.inspired-training.com

Mark Chase · 25th May 2006, 10:42

Quote:

"Literally there would be extremely bent people everywhere based on the sort of dives being done out there."

Actually no, at least not yet. But on this trend in a few years, no doubt it will happen (I'll spare you the computation). Today, it's a very small population of very good divers. But with democratization...

In the text we were told that using VPMB RGBM type deco we could expect a 10% rate of DCI incidents.

Our team are doing 45min exposure dives at 70+m on average 25 times a year with 8 divers so thats 200 exposures per year. In the last two years there has been one bend the cause of which we were fairly confident we knew.

So on 400 exposures we had 1 bend which is a 0.25% DCI hit rate in a 55 year old diver who drank way too much the night before the dive.

Looking around the boat I would say 50% of the divers are reasonably fit and 50% are overweight. All of the divers are over 40 years old with the eldest being 56.

Deco software varies from VR3 set on 0 safety, VPMB level 2 and Ambient Pressure Diving Vision software running GF deco 25/85.

With the 10% ratio put forward we should have suffered 40 bends in the last two years?

In fact despite the vast diving experience on the boat and some of the teem having carried out hundreds of dives in the apparent danger zone there is only a few that have ever been bent and then only once or twice.

Interestingly I aborted this weeks diving due to bad weather. The plan was 7 days 6 dives all below 70m max 95m and all in excess of the above proposed safety margin for bottom time.

I came home with a deep and nagging pain in my shoulder. I would definitely have gone to the chamber with this pain and had a treatment. However seeing as I only got wet loading and unloading the boat I didn't think it was necessary

ATB

Mark Chase

graham_hk · 25th May 2006, 11:17

Quote: (Originally Posted by Mark Chase)

With the 10% ratio put forward we should have suffered 40 bends in the last two years?

Be careful Mark - you are twisting statistics. Just as a illustration flip a coin. You get 10 heads in a row - whats the probability the 11th will be a head correct answer - 0.5 (or 50%)

Drmike · 25th May 2006, 11:18

Quote: (Originally Posted by jasondrake)

"

Any idea what Mark Ellyatt's using as a basis for comparison?

its all there in the pdf file i put up in this thread

http://www.rebreatherworld.com/49748-post36.html

Mark Chase · 25th May 2006, 12:35

Quote: (Originally Posted by graham_hk)

Be careful Mark - you are twisting statistics. Just as a illustration flip a coin. You get 10 heads in a row - whats the probability the 11th will be a head correct answer - 0.5 (or 50%)

Obviously your correct but at what point do figures become representative?

400 exposures? 4000?

I am aware of 5 diving teems doing this sort of diving which represents 50 ish divers in the UK there are probably a few more but i would be surprised if it's over 100-150 divers in the UK. its quite a small community and I am fairly sure we would have herd about them.

Our teem is pretty committed so if we say the average deep trimix diver does 15 dives a year over 60m and 40 min bottom time that still puts us on 2250 dives in the danger zone in the UK each year.

Ignoring all the incidents on dives less than 50m I don't believe we have 225 DCI incidents a year.

According to BSAC incident reports we don't have 225 DCI incidents a year even including the 1000's of recreational dives down to max 50m?

Worst year since records began was 2004 with 144 reported DCI incidents
In 2005 there were 110

ATB

Mark Chase

**nigelh** · 25th May 2006, 13:21

Quote: (Originally Posted by graham_hk)

Be careful Mark - you are twisting statistics. Just as a illustration flip a coin. You get 10 heads in a row - whats the probability the 11th will be a head correct answer - 0.5 (or 50%)

Huh?
Assuming Mark is talking about 400 dives for his group if the incident rate is 10% you would expect roughly 40 incidents. Only roughly but more than 30 and less than 50.

I think the 10% was for some of the "tables that could be downloaded from the internet". Is it just me that notices that every few years somebody comes up with a new way of calculating deco that promises to get you out of the water faster and then it gets 'refined' over the next few years to be like what we were using before? I think our Comdex man has seen some of these in their first incarnation.

25th May 2006, 09:20	#42 (permalink)
Mdemon SiegeEngine II Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Inspiration Classic Home Build Join Date: Feb 2007 Location: SWUK Posts: 1,906	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover Looking forward to wading through your post Brent! Looks interesting. Mark Ellyatt et al have been harsh critics of the various deco algorythms available for a while now. Worth a quick look at his website to scare yourself silly. I particularly liked the comparison of the various algorythms, critiqued. http://www.inspired-training.com/deco_comparisons.htm My take is that current software is all extrapolated mathematically from the initial man-/animal-tested work. As people get hurt, so more conservatism gets thrown into the mix. The evolution of RGBM and VPM (now b,e) would seem to bear this out. If Comex added their knowledge to the mix, even if less relevant because of the workload/support etc, this would be the first man-tested input into deco algorythms for years. How do we feel about being guinea pigs folks? Because that's currently what we are. __________________ www.southwestmafia.com "Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"
(Offline)

25th May 2006, 10:04	#43 (permalink)
jasondrake New Member Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Nov 2005 Location: Completely homeless Posts: 75	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover "ark Ellyatt et al have been harsh critics of the various deco algorythms available for a while now. Worth a quick look at his website to scare yourself silly. I particularly liked the comparison of the various algorythms, critiqued. " Any idea what Mark Ellyatt's using as a basis for comparison?
(Offline)

25th May 2006, 10:19	#44 (permalink)
Ben Field CK+Shearwater Current Rebreather/s: Classic Kiss Other Rebreather/s: Sport Kiss Join Date: Aug 2005 Location: London, England Posts: 1,571	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover Quote: (Originally Posted by jasondrake) Any idea what Mark Ellyatt's using as a basis for comparison? He uses http://www.inspired-training.com/decochek.htm Read through the sites, sounds all well and good if abit "brash" I quote- "As you can see, the Officers don't use BUBBLE models, so why would the Troops?" Not sure I really like the suggestion behind that but everyones entitled to their own opinion I guess... BEN __________________ www.hugsac.org.uk Beware Fridge Suck
(Offline)

25th May 2006, 10:32	#45 (permalink)
Sue Rebreather World Writer Current Rebreather/s: Megalodon Sport Kiss Other Rebreather/s: Join Date: Mar 2005 Location: Portugal Posts: 161	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl Quote: (Originally Posted by jasondrake) Any idea what Mark Ellyatt's using as a basis for comparison? This is a question/answer from an interview I've made last year to Mark Ellyatt: Question - Decompression software for planning the dives – which one, and why? M.E. - I like to use Decoplanner for dives up to 90metres, for deeper than this, there is nothing sufficiently reliable. I developed a program called DECOCHEK with a colleague Stephen Burton. This program analyses any dive, the diver plans the dive like normal then imports the run time into the analyzer. The program advises against inappropriate decompression stops and bad mix choices. Its very good even if I do say so myself. You can see details of it at www.inspired-training.com
(Offline)

25th May 2006, 10:42	#46 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,562	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover Quote: "Literally there would be extremely bent people everywhere based on the sort of dives being done out there." Actually no, at least not yet. But on this trend in a few years, no doubt it will happen (I'll spare you the computation). Today, it's a very small population of very good divers. But with democratization... In the text we were told that using VPMB RGBM type deco we could expect a 10% rate of DCI incidents. Our team are doing 45min exposure dives at 70+m on average 25 times a year with 8 divers so thats 200 exposures per year. In the last two years there has been one bend the cause of which we were fairly confident we knew. So on 400 exposures we had 1 bend which is a 0.25% DCI hit rate in a 55 year old diver who drank way too much the night before the dive. Looking around the boat I would say 50% of the divers are reasonably fit and 50% are overweight. All of the divers are over 40 years old with the eldest being 56. Deco software varies from VR3 set on 0 safety, VPMB level 2 and Ambient Pressure Diving Vision software running GF deco 25/85. With the 10% ratio put forward we should have suffered 40 bends in the last two years? In fact despite the vast diving experience on the boat and some of the teem having carried out hundreds of dives in the apparent danger zone there is only a few that have ever been bent and then only once or twice. Interestingly I aborted this weeks diving due to bad weather. The plan was 7 days 6 dives all below 70m max 95m and all in excess of the above proposed safety margin for bottom time. I came home with a deep and nagging pain in my shoulder. I would definitely have gone to the chamber with this pain and had a treatment. However seeing as I only got wet loading and unloading the boat I didn't think it was necessary ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
(Offline)

25th May 2006, 11:17	#47 (permalink)
graham_hk New Member Current Rebreather/s: RB80 / Clone Other Rebreather/s: Inspiration Classic Classic Kiss MK 15.X RB80 / Clone Join Date: Nov 2005 Location: Philippines Posts: 90	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover Quote: (Originally Posted by Mark Chase) With the 10% ratio put forward we should have suffered 40 bends in the last two years? Be careful Mark - you are twisting statistics. Just as a illustration flip a coin. You get 10 heads in a row - whats the probability the 11th will be a head correct answer - 0.5 (or 50%)
(Online)

25th May 2006, 11:18	#48 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,165	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover Quote: (Originally Posted by jasondrake) " Any idea what Mark Ellyatt's using as a basis for comparison? its all there in the pdf file i put up in this thread http://www.rebreatherworld.com/49748-post36.html __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
(Offline)

25th May 2006, 12:35	#49 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,562	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover Quote: (Originally Posted by graham_hk) Be careful Mark - you are twisting statistics. Just as a illustration flip a coin. You get 10 heads in a row - whats the probability the 11th will be a head correct answer - 0.5 (or 50%) Obviously your correct but at what point do figures become representative? 400 exposures? 4000? I am aware of 5 diving teems doing this sort of diving which represents 50 ish divers in the UK there are probably a few more but i would be surprised if it's over 100-150 divers in the UK. its quite a small community and I am fairly sure we would have herd about them. Our teem is pretty committed so if we say the average deep trimix diver does 15 dives a year over 60m and 40 min bottom time that still puts us on 2250 dives in the danger zone in the UK each year. Ignoring all the incidents on dives less than 50m I don't believe we have 225 DCI incidents a year. According to BSAC incident reports we don't have 225 DCI incidents a year even including the 1000's of recreational dives down to max 50m? Worst year since records began was 2004 with 144 reported DCI incidents In 2005 there were 110 ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System Last edited by Mark Chase : 25th May 2006 at 12:41.
(Offline)

25th May 2006, 13:21	#50 (permalink)
nigelh New Member Current Rebreather/s: Inspiration Vision Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Mar 2005 Location: Brighton, Sussex, UK Posts: 825	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover Quote: (Originally Posted by graham_hk) Be careful Mark - you are twisting statistics. Just as a illustration flip a coin. You get 10 heads in a row - whats the probability the 11th will be a head correct answer - 0.5 (or 50%) Huh? Assuming Mark is talking about 400 dives for his group if the incident rate is 10% you would expect roughly 40 incidents. Only roughly but more than 30 and less than 50. I think the 10% was for some of the "tables that could be downloaded from the internet". Is it just me that notices that every few years somebody comes up with a new way of calculating deco that promises to get you out of the water faster and then it gets 'refined' over the next few years to be like what we were using before? I think our Comdex man has seen some of these in their first incarnation. __________________ nigelh
(Online)

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