ICD and switch to nx38 from normoxic trimix

[ajduplessis]

It looks like the Suunto dive planner and V-Planner would use some percentage-only rule for ICD warnings, and would not take into account the amount of dissolved gas and other parameters. Am I correct?

I would assume that tissue compartment helium and nitrogen loadings, the ambient pressure, amount of supersaturation, the percentages of the new gas, and amount of perfusion would all affect this phenomenon in a complicated way. Am I correct? Surely it cannot be easier to model than ordinary offgassing.

Are there any dive planners in existence that attempt to model this properly, physically and statistically? Are there any mathematical ICD models in existence, with experimentally found parameters?

Ignoring oxygen clocks and stuff, I would guess that spending five hours at 45m on trimix 21% 02, 35% He, and then switching to EAN40 might be a problem (again, I might be wrong). Half an hour is not. I know it now.

A chef shortly explained to me some rules of thumb relating to ICD, that I have now forgotten, went on to declare it irrelevant to me, and didn't have a clue about the phenomenon (insert warm fuzzy feeling here). Such is the quality of recreational dive instruction. Recreational as in not commercial.

Please dont get PFcAJ started on O2 clocks

 

[Subcooled]

Hello,

You might find this useful.
Explaining Isobaric counter diffusion - Page 7

Simon M

This post made it wonderfully clear, for a diver. Thanks alot.

What is missing though (?) is an inner ear decompression model.

Are there other sites like this in the body? Reservoirs of badly/nonperfused liquid? At the joints?

 

[PfcAJ]

Please dont get PFcAJ started on O2 clocks

Or overfilling lp steel tanks.

 

[ajduplessis]

Great and fantastic! I take your word for it but will not dive that way. So IEDCS/IBCD will not happen above 270ft does not matter what you put in your mouth?

Back to the questions I asked that you seem to be ignoring. Ever lost a buddy diving with safe limits, or exceeding limits?

 

[PfcAJ]

Great and fantastic! I take your word for it but will not dive that way. So IEDCS/IBCD will not happen above 270ft does not matter what you put in your mouth?

Back to the questions I asked that you seem to be ignoring. Ever lost a buddy diving with safe limits, or exceeding limits?

It doesn't happen when you switch to 50%. Some other combo perhaps but not with the conditions you described.

Ive had one friend die cave diving. Breathed the wrong gas at depth. Is that the answer you wanted? Not sure how that's relevant to a discussion on ibcd.

 

[Subcooled]

Divers also die/get bent without any computer warnings. Real life enough for you? You have been around the block a couple of times. Every lost a buddy within safe limits? Ever lost a buddy exceeding limits?

Fortunately, I have never lost a buddy, but I know one who has lost many. He does not believe in the oxygen clock.

And no, my point is not the inexact oxygen clock, but the submitting acceptance of the inevitable, "I will get bent anyway". If I get bent, at least I tried to avoid it.

The body certainly is a complicated thing and cannot be fully modeled. Hence, some risk will remain. That has to be accepted. I know that models are not perfect and people still get bent. That is however not an excuse for not seeking the best available information. Trying to understand is... entertaining too.

All the divers I know, dive 21/35 or 18/45 with nitrox 50. Some use 50/5 with 18/45. Nobody uses 21/35 + nitrox 38. I don't like to extrapolate unless I have to. I let others do that. Personal preference

Anecdotal evidence ("I have done", "my friends have done", "people do" and so on) lacks detail. If I would see everyones dive logs, then things would obviously be easier to understand. My major concern is whether the profiles "done by all" remain safe in +2C water.

Anyway, thanks to the splendid posts above I now realize the the algorithms implemented in some dive planners give false warnings. This is valuable knowledge.

 

[PfcAJ]

Also to be clear I think oxygen is something that must be managed with careful attention. My argument is that the clock thing is a crappy model and not useful for determining oxygen toxicity risk.

 

[ajduplessis]

I am truely sorry to hear that. No, that was not the answer I was looking for.

My point was that IBCD is a potential risk even as shallow as 270ft. I appreciate you "accepting" (hope I can make that assumption) that some other gas combo could!

The only point I want to make is that it is a consideration instead of saying IBCD is a non-event shallow!
I have also lost a friend and want to become a safer diver based on what I have observed, not even sure if that possible.

 

[PfcAJ]

I certainly accept that icbd is a real thing. My point is that I see no real life evidence to suggest that a switch from 15/55 to 50% results in inner ear dcs. Literally every gue tech 2 class involves that exact same gas switch and no ones getting bent doing it.

Perhaps a switch from 10/80 to 50% would do it, but I don't know for sure of course.

 

[Subcooled]

Please dont get PFcAJ started on O2 clocks

Terribly sorry

---------- Post added January 10th, 2015 at 08:02 PM ----------

Also to be clear I think oxygen is something that must be managed with careful attention. My argument is that the clock thing is a crappy model and not useful for determining oxygen toxicity risk.

I know a person who is a living proof of that. He will die later.

---------- Post added January 10th, 2015 at 08:06 PM ----------

even as shallow as 270ft

ok...

...and what is DEEP? Are you guys saturation divers, or what?

I know that a dive to 650ft and one diluent flush too much can cause a major IEDCS hit. What is the most shallow known case?