BSAC technical Crossover Info

[TerryH]

Ok following on from the Where do we go from here thread.

Just to recap. We have a number of divers who are thinking
where next. Upto now BSAC has been fine, but some of the
advantages of other agencies seem quite attractive.

So .... Assume a start point of BSAC DL/Adv Nx and a good
record of quality minor deco UK dives. I'm looking to create a
simple list of options based on the above BSAC diver and
include all UK agencies.

Got anything else to add?

NB: Some of this may be incorrect. Please say so if it isnt,
but please add your credentials.

BSAC ERD
Cheap course compared to others. Gets 80% + accelerated deco,
but no EAD concept. If going onto tri with other agencies,
often seen as an inferior course and needs top ups (This may be
acedemic when BSAC tri comes out).

TDI Adv Nx
BSAC Adv only 50%, so entry level for TDI (100%) is this grade.
Lots of repeats on BSAC stuff, but includes EAD. No accelerated
deco. Not so good that dispite having been deco diving with BSAC
cant combine the two. So need to do .......

TDI Deco Procedures
Assumes no deco knowledge and again a repeat of lots already
done in DL & Adv. Assuming this course is primarily for no deco
divers like PADI/SSI etc. Entry level TDI Adv.
Two courses makes this and expensive option and you still might
want to go for.

TDI Extended Range



IANTD Technical Diver
Bit different in that the Instructor has the option of
accepting existing qualifications and skills on there own
merits. Has 100%, EAD & Accelerated deco. Based on the
flexibility DL/Adv Nx would be ok as entry level.
Training materials weak, but cheaper in comparison with TDI.

DSAT




Got lots of gaps. Anybody want to add there two cents worth?
Remember you have to look at it from a DL/Adv nitrox angle.

Rgds
TerryH

[Chris Cherrington]

IANTD Technical Diver
Bit different in that the Instructor has the option of
accepting existing qualifications and skills on there own
merits. Has 100%, EAD & Accelerated deco. Based on the
flexibility DL/Adv Nx would be ok as entry level.
Training materials weak, but cheaper in comparison with TDI.

DSAT


IANTD Decompression specialist??

Gives EAD + Deco software + 100%O2 (I think)

Would fill in the gaps anyway.

Chris

[mark jones]

what about GUE Dir Fundementals and then Tech 1.

I am in the same position as you suggest and Fundementals will probably be my next course.

[TerryH]

what about GUE Dir Fundementals and then Tech 1.

I am in the same position as you suggest and Fundementals will probably be my next course.

Sorry, we are a very diverse bunch and I'm absoluletly sure that
we wouldnt fit in with GUE standards.

T.

[TerryH]

:=IANTD Technical Diver
:=Bit different in that the Instructor has the option of
:=accepting existing qualifications and skills on there own
:=merits. Has 100%, EAD & Accelerated deco. Based on the
:=flexibility DL/Adv Nx would be ok as entry level.
:=Training materials weak, but cheaper in comparison with TDI.
:=
:=DSAT
:=

IANTD Decompression specialist??

Gives EAD + Deco software + 100%O2 (I think)

Would fill in the gaps anyway.

Chris

So what's the entry level and would that be 100% O2 + A.Deco?

T.

[Nigel Hewitt]

Just to recap. We have a number of divers who are thinking where next. Upto now BSAC has been fine, but some of the advantages of other agencies seem quite attractive.

Our DO arranged a combined TDI ERD (not sure exact name) and Normoxic Trimix course. He did it too along with his predecessor as DO. We are expecting helium in the compressor room shortly and the dive list for the year should be interesting.

It is a stated intention that although we train a lot of novices every year nobody should have to feel they have 'outgrown' the club.

[nick kay]

BSAC ERD
Cheap course compared to others. Gets 80% + accelerated deco,
but no EAD concept. If going onto tri with other agencies,
often seen as an inferior course and needs top ups (This may be acedemic when BSAC tri comes out).

I did BSAC ERD with Graeme Bruce, followed by TDI Entry Level Trimix with Jack Ingle - not aware I had to do any "topups"

[Chris Cherrington]

:=IANTD Decompression specialist??
:=
:=Gives EAD + Deco software + 100%O2 (I think)
:=
:=Would fill in the gaps anyway.
:=
:=Chris

So what's the entry level and would that be 100% O2 + A.Deco?

T.


From the standards:

Decompression Specialist
A. Purpose
1. This Program is designed to give the diver a better and deeper understanding of the models used for generating dive tables and dive computer profiles. The program will also train students to use dive tables, dive computers and decompression
software programs.
2. Upon completion of this course dives will be made to 130 fsw (30 msw) using EAN 50 to 100 % oxygen for decompression provided no stops are deeper than 20 fsw (6 msw) or longer than 10 minutes
B. Prerequisites
1. Must be a qualified Advanced EANx diver or equivalent.
C. Texts
1. IANTD Decompression Software Specialist Student Workbook.
2. IANTD Encyclopedia of Technical Diving.
3. CD-ROM Decompression Software Specialist.
D. Program Content
1. Complete all theory in the IANTD Decompression Software Specialist Student Workbook.
2. Complete the written exam with a minimum score of 80%.
3. Demonstrate the use of decompression software.
E. Equipment Requirements
1. There are no specific equipment requirements for this Program.
F. Program Limits
1. There are no diving activities required for this Program.
G. Water Skills Development
1. There are no specific water skills required for this Program.

IE its classroom based but will give you a ticket to get O2 at 100%.

If I read it right?

Chris

[Mark Powell]

TDI Adv Nx
BSAC Adv only 50%, so entry level for TDI (100%) is this grade.
Lots of repeats on BSAC stuff, but includes EAD. No accelerated
deco. Not so good that dispite having been deco diving with BSAC
cant combine the two. So need to do .......

TDI Deco Procedures
Assumes no deco knowledge and again a repeat of lots already
done in DL & Adv. Assuming this course is primarily for no deco
divers like PADI/SSI etc. Entry level TDI Adv.
Two courses makes this and expensive option


A combined Adv and Deco course can be tailored to suit your needs. TDI instructors also have the option of evaluating existing qualificatons and experience. As BSAC DL you have deco experience and so this can be credited on the course. Deco Procedures is a flexible course that can be adapted depending on your previous deco experience. In addition by combining the two courses the cost will be less than doing them seperately.

In your situation I would probably recommend a combined course.

Extended Range is only of use if you want to do deeper diving on air. Not really recommended but as the BSAC limit is 50m then if you are going to dive to 50m an ERD course is a way of trying to add in some safety. As a BSAC DL and Adv Nitrox then it may be possible to go straight onto TDI ERD but only if your instructor is satisfied that you have the experience to go along with it.

In most cases it is worth having a chat to your instructor and explaining your personal diving experience and qualifications. Most good instructors will be happy to put together a specific package for a group which addresses exactly what you need.

Mark Powell
TDI Instructor

[Mike Rowley]

Ok following on from the Where do we go from here thread.

Just to recap. We have a number of divers who are thinking
where next. Upto now BSAC has been fine, but some of the
advantages of other agencies seem quite attractive.

So .... Assume a start point of BSAC DL/Adv Nx and a good
record of quality minor deco UK dives. I'm looking to create a
simple list of options based on the above BSAC diver and
include all UK agencies.

Got anything else to add?



BSAC ERD
Cheap course compared to others. Gets 80% + accelerated deco,
but no EAD concept. If going onto tri with other agencies,
often seen as an inferior course and needs top ups (This may be
acedemic when BSAC tri comes out).


Terry

BSAC ERD will allow entry into BSAC trimix course. The BSAC trimix course for OC and CCR are shceduled to be launched by spring 2006, we are currently working on them.

BSAC ERD will allow you to use 100% but within a maximum PO2 of 1.4 bar, this is currently the BSAC recommendation. In view of the ox-tox incident in 2004 due to 1.6 bar PO2 at deeper than 6m this is unlikely to be modified in the short term but we intend to look at it again at trimix level. EAD concept may not be used with the BSAC 88 tables, as you may know, we are still awaiting some form of explanation on this from Tom Hennesey however, it is entirely possible for the BSAC ERD instructor to teach EAD as a concept and with other decompression tools. EAD/END will be essential for trimix courses.

So if you would like to continue within the BSAC system the means is there for you to do so for your needs in the short term and will be in place in the medium term to progress further.

Cheers

Mike
BSAC Technical Development Leader

[iainmsmith]

PLEASE NOTE:

This post (and the rest of this Branch of the thread) arose due to there being a second OxTox incident which did not make it into the 2004 Incident Report and which I was therefore unaware of. Mike's later description suggests that they were definitely not the same incident. My comments here are therefore valid, but do not necessarily follow from the thread that preceeded it! Sorry! I.

BSAC ERD will allow you to use 100% but within a maximum PO2 of 1.4 bar, this is currently the BSAC recommendation. In view of the ox-tox incident in 2004 due to 1.6 bar PO2 at deeper than 6m this is unlikely to be modified in the short term.

[I only recall one oxtox from the Incident Report and, having searched the on-line Report, have only found that one incident. Mike - if you are referring to a different incident, could you provide a reference or details, please.]

Purely for context, it is worth keeping in mind that the incident report for the above includes the following:

The casualty's "...dive computer showed that she made a normal ascent to 23m, then a gradual descent to 30m then a rapid ascent to the surface in less than 1 min. It is thought that the casualty switched to her decompression gas [53%] before sinking back down to 30m....It was thought that breathing 53% oxygen at 30m may have induced oxygen toxicity."
- Incident 04/236 in BSAC NDC Diving Incidents Report 2004, "Fatalities", p7

This was a diver who _may_ have been breathing at a PO2 of 2.12bar - the equivalent of breathing O2 at 11.2m - which no-one (AFAIK) is advocating. I'm taking it as read that a certified BSAC ERD/Trimix diver will have demonstrated an ability to hold stops with a little more precision than that.

Secondly, while the conclusion reached about oxtox is not unreasonable (especially if the gas pressure in the deco cylinder was reduced by an amount consistent with having been breathing from it during the re-descent [which is information not included in the published report]), there is nothing in the report to prove oxtox as opposed to panic at 30m due to loss of control of the ascent, hitting the inflator and bursting a lung on ascent. (I note that the actual mechanism of death is not reported, though a burst lung and/or drowning would be reasonable speculation in the case of a casualty who either arrived or became rapidly unconscious on the surface and (appears not to have) regained consciousness at any point.)

The Incident Report's author may, of course, have access to additional information such as a post-morten report which might make a conclusion of oxtox more or less likely. Again, such information is not available in the Report.

Purely based on my observations of a number of fits in the Emergency Department, resulting from various causes, hitting the inflator button seems a remarkably co-ordinated thing to have done immediately before a fit, although not necessarily impossible.

In short, while it is important to give due consideration to such incidents, I hope that those responsible for determining the maximum allowable PO2 within BSAC will not give what I would regard as undue weight to this incident, where the oxygen pressure to which the casualty may have been exposed is in excess of 32% higher than anything proposed as an alternative maximum.

[Declared conflict of interest: I am TDI Trimix-certified to use a PO2 of 1.6 bar and am in favour of BSAC increasing the maximum PO2 to 1.6 bar]

Iain

[Nigel Hewitt]

>>BSAC ERD will allow you to use 100% but within a maximum PO2 of 1.4 bar, this is currently the BSAC recommendation. In view of the ox-tox incident in 2004 due to 1.6 bar PO2 at deeper than 6m this is unlikely to be modified in the short term.

>The casualty's "...dive computer showed that she made a normal ascent to 23m, then a gradual descent to 30m then a rapid ascent to the surface in less than 1 min. It is thought that the casualty switched to her decompression gas [53%] before sinking back down to 30m....It was thought that breathing 53% oxygen at 30m may have induced oxygen toxicity."
- Incident 04/236 in BSAC NDC Diving Incidents Report 2004, "Fatalities", p7

Are you sure this is the incident Mike is refering too?
I don't see a 1.6bar smoking gun anywhere in this sad case.

[iainmsmith]

:=>>BSAC ERD will allow you to use 100% but within a maximum PO2 of 1.4 bar, this is currently the BSAC recommendation. In view of the ox-tox incident in 2004 due to 1.6 bar PO2 at deeper than 6m this is unlikely to be modified in the short term.

:=>The casualty's "...dive computer showed that she made a normal ascent to 23m, then a gradual descent to 30m then a rapid ascent to the surface in less than 1 min. It is thought that the casualty switched to her decompression gas [53%] before sinking back down to 30m....It was thought that breathing 53% oxygen at 30m may have induced oxygen toxicity."
:= - Incident 04/236 in BSAC NDC Diving Incidents Report 2004, "Fatalities", p7

Are you sure this is the incident Mike is refering too?

I can't find any other reference to "oxygen toxicity", "ox-tox" or "oxtox" in the Incident Report. If I'm wrong, I'm sure Mike will point this out (but I will add a disclaimer to my post in case I am!)

I don't see a 1.6bar smoking gun anywhere in this sad case.

That was my point...(the diver may have switched to a 53% mix at 23m, getting a PO2 of a bit more than 1.6 bar, but was then exposed to a significantly higher PO2 which may or may not have resulted in Oxtox)

Iain

[Mike Rowley]

:=
:=Are you sure this is the incident Mike is refering too?

I can't find any other reference to "oxygen toxicity", "ox-tox" or "oxtox" in the Incident Report. If I'm wrong, I'm sure Mike will point this out (but I will add a disclaimer to my post in case I am!)

:=I don't see a 1.6bar smoking gun anywhere in this sad case.

That was my point...(the diver may have switched to a 53% mix at 23m, getting a PO2 of a bit more than 1.6 bar, but was then exposed to a significantly higher PO2 which may or may not have resulted in Oxtox)

Iain, Nigel,

The incident in question was raised in a discussion on PO2 that I was involved in as part justification for retaining the status quo for BSAC. I am unsure of the provinance of the incident since I haven't researched it myself but will make enquiries. It maybe that it was not in the 2004 incidents report, either because it was too late to be included in 2004 or it wasn't captured.

The incident as explained briefly to me was a diver decompressing at 6m on oxygen failed to maintain depth and drifted to 7-8m.

If I find more I will post.

Mike

[David Walker]

The incident as explained briefly to me was a diver decompressing at 6m on oxygen failed to maintain depth and drifted to 7-8m.

This is the one thing about the whole 1.4 / 1.6ppO2 thing I don't like - it does appear that BSAC don't have confidence in their training, and specifically on Adv Nitrox, otherwise this wouldn't be an issue. With 1.6 already considered a safe limit, are BSAC divers so bad that we need extra safety built on top?

I should note that I don't use stage cylinders to deco on at present, so this is nothing that directly affects me at the minute, but the arguments behind it do seem to be a little, well, odd!

David

[Edit: because it didn't make much sense the first time!]

[Nigel Hewitt]

The incident as explained briefly to me was a diver decompressing at 6m on oxygen failed to maintain depth and drifted to 7-8m.

If I find more I will post.

I would appreciate that. It still feels like we are legislating against the wrong thing. This has the feel of outlawing beer to stop drink driving.

To put this in context so the others know why I care about 0.2bar: One of the key rebreather trimix drills for dead sensors, batteries or electronics is to get to 6m (where the bulk of your stop time is scheduled) flush with oxygen and run on the only mix you can be sure of. If I have to pull this on a club dive and just as I am surfacing I get creamed by a Jetski I don't want anybody giving my DO a hard time at the inquest.

[iainmsmith]

The incident in question was raised in a discussion on PO2 that I was involved in as part justification for retaining the status quo for BSAC. I am unsure of the provinance of the incident since I haven't researched it myself but will make enquiries. It maybe that it was not in the 2004 incidents report, either because it was too late to be included in 2004 or it wasn't captured.

The incident as explained briefly to me was a diver decompressing at 6m on oxygen failed to maintain depth and drifted to 7-8m.

If I find more I will post.

Mike,

Thanks for looking into it.

Iain

[gareth]

:
This is the one thing about the whole 1.4 / 1.6ppO2 thing I don't like - it does appear that BSAC don't have confidence in their training, and specifically on Adv Nitrox, otherwise this wouldn't be an issue. With 1.6 already considered a safe limit, are BSAC divers so bad that we need extra safety built on top?

David

I think the reason the BSAC settled on 1.4po2 goes back to the original guidelines for high Po2 mixes by all the technical agency's in the early 1990's.

When I did my IANTD coarse many years ago, it was very heavily emphasised that a po2 of 1.6 was acceptable in ideal conditions. For every adverse condition you should remove 0.1 these included
a/ Dark or low light conditions
b/ High work load, tide, swimming, etc
c/ Cold water
d/ High physical or mental stress

There may have been others, but basically UK diving put you back to 1.4po2 very quickly.
When I subsiquently did my TDI Trimix coarse the same rules were again reiterated, 'a bottom mix should not exced 1.4po2'.
The po2 for Decompression could be as high as 1.6 because the work load, stress should be very low /negligible. We were also advised that it may be better to restrict the po2 on decompression to 1.5 because of the CNS, UPTD(OTU) loading, in attempt to avoid reaching 300 units. If it was not practical to stay below the 300 units then air breaks would be required.

Cheers

Gareth

[matt]

:
:=This is the one thing about the whole 1.4 / 1.6ppO2 thing I don't like - it does appear that BSAC don't have confidence in their training, and specifically on Adv Nitrox, otherwise this wouldn't be an issue.:=There may have been others, but basically UK diving put you back to 1.4po2 very quickly.
When I subsiquently did my TDI Trimix coarse the same rules were again reiterated, 'a bottom mix should not exced 1.4po2'.

I think there is some justification for limiting decompression PPO to 1.4 on Advanced. The Adv Nx course is the introductory level for hi FO2 Nitrox decompression, so a safety factor is logical and progressive. The actual difference that 1.4 Vs 1.6 is going to make to decompression on 50% is negligible due to the relatively short stop time required to make a switch. It takes a couple minutes to saturate plasma with O2 molecules, but once that has occurred remaining at 20m+ is likely to do more harm than good as the slowest tissues continue to saturate with N2.

The po2 for Decompression could be as high as 1.6 because the work load, stress should be very low /negligible. We were also advised that it may be better to restrict the po2 on decompression to 1.5 because of the CNS, UPTD(OTU) loading, in attempt to avoid reaching 300 units. If it was not practical to stay below the 300 units then air breaks would be required.

Not sure about that. The REPEX table I am looking at allows 850 units for a single days diving. The limit falls for multi-day diving, down to a minimum of 300 units per day for multi-day series exceeding 10 consecutive days. So on a single days diving you could do a total of 7hrs of deco at 1.6 PPO, and on an 11 day series you could do 2.5 hours a day at 1.6. You need to allow for the bottom time, but OTUs are rarely a problem for OC technical divers.

OTU limits are primarily intended to reduce or avoid the long term health problems assosciated with breathing high concentrations of O2. AFAIK the doom mongers used to claim that chambers might refuse to treat technical divers if the HBOT schedule would over-run the REPEX limits. This is a highly unlikely situation. AIUI no reputable medical organisation is going to refuse an immediate treatment on the basis that it might cause a longer term problem. Similar to avoiding chest X-Rays, avoiding the REPEX limits is desireable, but if breaking such is required to treat an immediate and serious health risk, like DCI, so be it.

You have to be a bit more careful with CNS, particularly using 100% O2 or CCRs. CNS limits are intended to avoid the seizures associated with short term hyperbaric Oxygen use. Unlike long term pulmonary damage, acute ox-tox whilst underwater tends to cause immediate death by drowning.

The 80% CNS limit often quoted is quite conservative and still allows up to 35 minutes at 1.6 before air breaks are required. CNS loading can be reduced by lowering the PPO of the final stop by making the stop shallower. A shallower stop increases the dissolved/inspired inert gradient further which offsets the lower PPO. Making the final stop at 5m on 100% O2 reduces PPO to 1.5 and the CNS per minute loading more than halfs to 0.83, or 90 minutes before the 80% CNS limit is reached. Reducing the FO2 is another way to avoid CNS limits, even completeing the shallow stop at 6m, would give you around 2Hrs before the 80% limit is reached.

Admittedly BSAC do seem engrained with the 6m final stop which might explain why the PPO limit is so conservative. Accepting that 3m is too shallow for a stable decompression in the UK, that still leaves depths between 3m and 6m. With a little practise a 4m to 5m stop is perfectly comfortable in all but the most marginal seas. Debateably the Adv Nx limit of 50% as a safety gas starts to make a bit of sense as it provides a margin while perfecting shallower stops prior to ERD/Technical training and the additional risks that accelerated decompression entails.

[matt]

I would appreciate that. It still feels like we are legislating against the wrong thing. This has the feel of outlawing beer to stop drink driving.

How about we ban diving because tragically people have drowned after running out of breathing gas!

[gareth]

MattS

You are correct about the single does recommendations in the REPEX table. I hadn't even looked at the single dose recomendations, I always tend to think in terms of repetitive dive planning & the 300 unit recomendation!
In all honesty I don't think I have ever reached the 300 unit level anyway, (I have come close on the CNS).
I do remember reading somewere that CC can have a problem with exposure time to high pO2 causing short term vision problems (repetative dive series) - but this is not relevent to this discussion.

My original point was that in the early 90's we were being recommended to reduce the PO2 anyway for the main section of the dive for adverse conditions - which is how most of the american agency's viewed UK diving!

I think the other point to be remembered is that when the BSAC introduced Nitrox. There had been a lot of resistance to Nitrox at the time - it being the 'devil gas'. So the BSAC was being conservative with its guidelines.


Gareth

[iainmsmith]

It takes a couple minutes to saturate Haemoglobin with O2 molecules,

Did you mean "to saturate _plasma_"? Haemoglobin is effectively saturated at 0.21 bar of O2 - it has no additional carrying capacity. The extra oxygen carriage in both acclerated deco and oxygen first aid comes from Henry's law of gas solubility in liquid (ie the amount of oxygen that can be carried in plasma is proportional the the PO2 to which the plasma is exposed).

Iain

[Mike Rowley]

Ok, these are the details of the incident. I'm not going to state the date or place of the incident since I understand the family would not wish it.

a pair of divers descended the shot-line to 36m, They obviously failed to find the shot-line on return and fired up a DSMB. They had planned to decompress on 100% oxygen at 6m for 15 minutes. One of the pair had a convulsion, went unconscious and was lifted to the surface by his buddy. They claimed that they had held their depth a 6m. On downloading the computers they found that they had an average depth of 7m during the decompression phase. They where IANTD tri-mix technical divers with a PADI background.


To put this in context so the others know why I care about 0.2bar: One of the key rebreather trimix drills for dead sensors, batteries or electronics is to get to 6m (where the bulk of your stop time is scheduled) flush with oxygen and run on the only mix you can be sure of. If I have to pull this on a club dive and just as I am surfacing I get creamed by a Jetski I don't want anybody giving my DO a hard time at the inquest.

If you got creamed by a jet ski or tupper ware tart trap jockey Nigel your DO would face no hard time. There would be no insurance ramifications either as clearly the fact that you had been breathing oxygen at 6m contributed nothing to the incident.

Cheers

Mike

[matt]

:= It takes a couple minutes to saturate Haemoglobin with O2 molecules,

Did you mean "to saturate _plasma_"? Haemoglobin is effectively saturated at 0.21 bar of O2 - it has no additional carrying capacity. The extra oxygen carriage in both acclerated deco and oxygen first aid comes from Henry's law of gas solubility in liquid (ie the amount of oxygen that can be carried in plasma is proportional the the PO2 to which the plasma is exposed).

Thank you for the correction Iain. I have corrected the OP.

Having checked my reference, I got my torrs, kPas and Bars in a muddle. Hb is pretty much saturated at .12 bar (which turns into 1.2 bar when I stupidly got the conversion factor wrong ;-(.

Does plasma saturate at around 1bar? I went through this once and seem to recall 1ish bar being significant. Microbiology is not my strong subject. I can just about follow stuff like this.

[Nigel Hewitt]

Does plasma saturate at around 1bar? I went through this once and seem to recall 1ish bar being significant.

As I understand it Hemoglobin works well at 0.21 but starts to drop off seriously below that so at about 0.16 you are in danger of just falling over. (Some people can go much lower especially if conditioned to high altitudes).

Plasma is just the usual gas dissolved in a liquid stuff. At the sort of pressures we are dealing with dissolved gas is proportional to applied partial pressure when it settles and settling time across the alveoli (thousandths of an inch) is fractions of a second. I have no idea how much ppO2 you would need to be exposed to so that that would become a significant factor in oxygen transport.

I've never seen the clip-on-finger blood oxygen meter used in hospitals read anything other than 98% or so but perhaps that's just me being lucky.

[Nigel Hewitt]

If you got creamed by a jet ski or tupper ware tart trap jockey Nigel your DO would face no hard time. There would be no insurance ramifications either as clearly the fact that you had been breathing oxygen at 6m contributed nothing to the incident.

I was just looking for a reason why I might get hauled out after a dive cold and the poor guy might get some flack if he knew my bail out plans involve 1.6bar.

[matt]

As I understand it Hemoglobin works well at 0.21 but starts to drop off seriously below that so at about 0.16 you are in danger of just falling over. (Some people can go much lower especially if conditioned to high altitudes).

AIUI What you are describing is called the Oxygen dissociation curve. Have a look at this;
<a href="http://members.aol.com/Bio50/LecNotes/lecnot20.html" >http://members.aol.com/Bio50/LecNotes/lecnot20.html</a>
FYI 100 mmHg is about 0.13 bar

Plasma is just the usual gas dissolved in a liquid stuff. At the sort of pressures we are dealing with dissolved gas is proportional to applied partial pressure when it settles and settling time across the alveoli (thousandths of an inch) is fractions of a second. I have no idea how much ppO2 you would need to be exposed to so that that would become a significant factor in oxygen transport.

I think I found what I was thinking about in a post by Eric Maiken
"now consider that O2 is both dissolved in blood and bound to
haemoglobin. the amount dissolved in the blood is: solubility*pressure;
so, the more pressure, the more dissolved. different tissues extract O2
from circulation at different rates. once enough dissolved O2 is present
to satisfy a particular tissue's needs, the O2 window levels off to a
constant."
<a href="http://www.aquanaut.com/bin/mlist/aquanaut/techdiver/display?8282,subject" >http://www.aquanaut.com/bin/mlist/aquanaut/techdiver/display?8282,subject</a>


I've never seen the clip-on-finger blood oxygen meter used in hospitals read anything other than 98% or so but perhaps that's just me being lucky.

Changes in blood Ph and temperature can shift the curve left or right. Anemia causes the curve to flatten. So you are not lucky, just normal ;-)

[Nigel Hewitt]

Thanks Matt. Interesting stuff.

[iainmsmith]

Ok, these are the details of the incident. I'm not going to state the date or place of the incident since I understand the family would not wish it.

Understood.

a pair of divers descended the shot-line to 36m, They obviously failed to find the shot-line on return and fired up a DSMB. They had planned to decompress on 100% oxygen at 6m for 15 minutes. One of the pair had a convulsion, went unconscious and was lifted to the surface by his buddy. They claimed that they had held their depth a 6m. On downloading the computers they found that they had an average depth of 7m during the decompression phase. They where IANTD tri-mix technical divers with a PADI background.

Thanks for the details.

Iain

[JohnDuncan]

BSAC ERD will allow entry into BSAC trimix course. The BSAC trimix course for OC and CCR are shceduled to be launched by spring 2006, we are currently working on them.
Mike
BSAC Technical Development Leader

Has there been any of your findings from your research into designing a BSAC trimix course published in a draft form maybe for input from BSAC members already qualified?

[Mike Rowley]

:=
Has there been any of your findings from your research into designing a BSAC trimix course published in a draft form maybe for input from BSAC members already qualified?

Not yet, we are in the early stages of course development. The people developing the courses are all experienced trimix divers and instructors on both rebreathers and open circuit.

I don't intend to publish any material in draft form, the only material we will publish is the finished item, all of the revision and proof reading will be done by a sub-group formed specifically for that purpose. Anyone wishing to be part of that sub-group should email me off forum with details of their certification and experience.(see latest NDC bulletin).

Cheers

Mike
BSAC Tecnical Development Leader
<a href="mailto:techdev@BSAC.com">techdev@BSAC.com</a>

[dano]

CAN THIS COURSE BE RUN IN THE UK ?????? IF SO WHAT CENTRES DO IT????




:=:=IANTD Decompression specialist??
:=:=
:=:=Gives EAD + Deco software + 100%O2 (I think)
:=:=
:=:=Would fill in the gaps anyway.
:=:=
:=:=Chris
:=
:=So what's the entry level and would that be 100% O2 + A.Deco?
:=
:=T.
:=

From the standards:

Decompression Specialist
A. Purpose
1. This Program is designed to give the diver a better and deeper understanding of the models used for generating dive tables and dive computer profiles. The program will also train students to use dive tables, dive computers and decompression
software programs.
2. Upon completion of this course dives will be made to 130 fsw (30 msw) using EAN 50 to 100 % oxygen for decompression provided no stops are deeper than 20 fsw (6 msw) or longer than 10 minutes
B. Prerequisites
1. Must be a qualified Advanced EANx diver or equivalent.
C. Texts
1. IANTD Decompression Software Specialist Student Workbook.
2. IANTD Encyclopedia of Technical Diving.
3. CD-ROM Decompression Software Specialist.
D. Program Content
1. Complete all theory in the IANTD Decompression Software Specialist Student Workbook.
2. Complete the written exam with a minimum score of 80%.
3. Demonstrate the use of decompression software.
E. Equipment Requirements
1. There are no specific equipment requirements for this Program.
F. Program Limits
1. There are no diving activities required for this Program.
G. Water Skills Development
1. There are no specific water skills required for this Program.

IE its classroom based but will give you a ticket to get O2 at 100%.

If I read it right?

Chris