heliox deco software

[SUBMERGETHEURGE]

are there any software packages that allows for helium leaving the tissues faster than nitrogen?
my question comes from the point of using ccr for deep diving. to use a diluent of trimix for the descent and deep portion of the dive, and to switch to a heliox diluent for the ascent and decompression. my thinking is that the trimix should keep the absorption of helium to a minimum, while the switch to heliox should give the optimum pressure gradient to off-gas the nitrogen with of course the increasing percentage of o2 to help along the way.
all the software i have come across so far seem to penalise the diver quite heavily.
bearing in mind that we are using heliox to treat minor bends successfully, this would seem to suggest that the heliox is in fact a better gas to decompress on than nitrox and maybe better than pure o2. would love to hear any thoughts on this.

 

[Dr Deco]

Hello SUBMERGETHEURGE:

Actually, all decompression algorithms allow for a difference in the diffusion and solubility of helium and nitrogen in tissues. For most diving operations, helium is a better gas from several standpoints. It is, however, quite costly and this limits its use for most shallow-water diving.:umnik:

Dr Deco :doctor:

 

[SUBMERGETHEURGE]

Hello SUBMERGETHEURGE:

Actually, all decompression algorithms allow for a difference in the diffusion and solubility of helium and nitrogen in tissues. For most diving operations, helium is a better gas from several standpoints. It is, however, quite costly and this limits its use for most shallow-water diving.:umnik:

Dr Deco :doctor:

thank you for the reply, unfortunately it didn't really cover the question.
i realise that helium is expensive, this was one of the reasons i went over to closed circuit rebreathers. from using heliox 80/20 for in water recompression we were also of the understanding that this was better for us than oxygen, firstly for the benefit of cutting out the air breaks and secondly for the pressure gradient in the tissues allowing the helium to come out as well as the nitrogen. but if its so good for deco why are we kept in the water longer for using it.

 

[Dr Deco]

I am afraid that helium saturates the tissues faster than nitrogen. That is its main drawback.

 

[Saturation]

thank you for the reply, unfortunately it didn't really cover the question.
i realise that helium is expensive, this was one of the reasons i went over to closed circuit rebreathers. from using heliox 80/20 for in water recompression we were also of the understanding that this was better for us than oxygen, firstly for the benefit of cutting out the air breaks and secondly for the pressure gradient in the tissues allowing the helium to come out as well as the nitrogen. but if its so good for deco why are we kept in the water longer for using it.

To second Dr. Deco, He use will exact a penalty as far the time needed to offgas. What is provided by many decompression programs takes into account the physics as we know it now, and given that tissue half times are essentially constants, its usage in deco gases will prolong your schedules.

If you follow a precept of using N2 time as the He time and getting out of the water based on N2 time, you will bubble out quite a bit more, whether this leads to bends is uncertain.

Since He offgasses faster than N2 and thus leaves your tissues 'cleaner', you may theoretically get the same results as 100% without the same pp02 exposure, relying on a type of countercurrent mechanism to drive N2 out of tissues replaced by He. Heliox has been shown of benefit in bends treatment but strictly speaking it has not been tested in in-water decompression as superior to 02.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9074400

and animals:


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11299250

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8061554

 

[BigJetDriver]

thank you for the reply, unfortunately it didn't really cover the question.
i realise that helium is expensive, this was one of the reasons i went over to closed circuit rebreathers. from using heliox 80/20 for in water recompression we were also of the understanding that this was better for us than oxygen, firstly for the benefit of cutting out the air breaks and secondly for the pressure gradient in the tissues allowing the helium to come out as well as the nitrogen. but if its so good for deco why are we kept in the water longer for using it.

Try reading "Technical Diving in Depth" by B.R. Wienke, if you have not already. The full-up iteration of RGBM, as represented in GAP, the H-S Explorer, and the NAUI tables is the best program for handling helium. A CCR is the best diving machine for maximizing your deco program effectiveness. The deep-stops even the score a bit in terms of times.

The Docs are certainly right about the physics and physiology of the situation as we know it today. Their advice is, as always, "cutting edge"!

Rob Davie