Wesley Skiles' widow suing over rebreather

[wedivebc]

First of all, it's not MY method.

Second of all, it's not stupid, it may be (in someone's view) wasteful of gas.

Third, the claim is repeatedly made that it is dangerous, but no one seems to be able to make a real case for the danger.

Fourth, we continuously have folks who have seem to have every certification card on earth but do not provide a more insightful and definitive explanation than, "you're stupid."

Perhaps that's just way the Master Chief taught the "eggheads" so there was a one solution solves all arrangement for folks who had no issues dealing with buoyancy changes and such, which carries over from O/C and drysuit use. HIGHwing's explanation of "trust but verify" makes some sense.

I took a look at the rebreatherworld column, frankly it does not look a whole lot different from what I see here, except for the few pedants over there who provide Dalton's law calculations to support their explanations, something that we seem to take for granted here, but that's about it.

---------- Post Merged at 07:08 AM ---------- Previous Post was at 07:08 AM ----------

First of all, it's not MY method.

Second of all, it's not stupid, it may be (in someone's view) wasteful of gas.

Third, the claim is repeatedly made that it is dangerous, but no one seems to be able to make a real case for the danger.

Fourth, we continuously have folks who have seem to have every certification card on earth but do not provide a more insightful and definitive explanation than, "you're stupid."

Perhaps that's just way the Master Chief taught the "eggheads" so there was a one solution solves all arrangement for folks who had no issues dealing with buoyancy changes and such, which carries over from O/C and drysuit use. HIGHwing's explanation of "trust but verify" makes some sense.

I took a look at the rebreatherworld column, frankly it does not look a whole lot different from what I see here, except for the few pedants over there who provide Dalton's law calculations to support their explanations, something that we seem to take for granted here, but that's about it.

If you flush with air at depth and ascend without adding additional oxygen your PO2 will be less than 0.21 at the surface if you need help with Dalton's law formula to work that out then what are you doing anywhere near a rebreather?

 

[Thalassamania]

If you flush with diluent you can then check your sensors and, depending on the the depth, the CCR will start adding oxygen; and you can watch the ppO2 in the loop rise. As far as Dalton's law is concerned, I've been teaching it longer than I expect you've been alive. You starting to grasp (or is it gasp) at straws with asinine insults and it does not become you. If you want to make this into a flame-fest ... go find another victim, I'm not interested.

---------- Post Merged at 09:50 AM ---------- Previous Post was at 09:50 AM ----------

If you flush with diluent you can then check your sensors and, depending on the the depth, the CCR will start adding oxygen; and you can watch the ppO2 in the loop rise. As far as Dalton's law is concerned, I've been teaching it longer than I expect you've been alive. You starting to grasp (or is it gasp) at straws with asinine insults and it does not become you. If you want to make this into a flame-fest ... go find another victim, I'm not interested.

 

[decompression]

Gentlemen, stay civil but please continue this debate as I for one with limited CCR exposure am dissecting each point. I'm sure many more are benefiting from this discussion. Even at the risk of giving Dave credibility, lol.

 

[HIGHwing]

Webdivedc -

Your argument really doesn't make any practical sense. You're ignoring the assumption the diver remains in charge thereby controlling the PO2. Just because you perform a Dil flush at any depth doesn't mean you're required to stick with the resulting PO2 for any portion of the dive.

If I'm holding a SP of 1.2 and flush at 66fsw my resulting PO2 will reduce to .63. Seconds after that flush the Hammerhead is going to start injecting oxygen to create a PO2 of 1.2 once again with no interaction from me whatsoever though I will probably have to blow off a little gas to maintain minimum loop volume.

If you're making a Dil flush prior to the ascent you're going to drop your PO2, but does breathing without oxygen injection. Clearly, oxygen injection, semi closed circuit mode, or bailout is required if you intend to surface once you've performed an Air-Dil Flush at depth. You have to have some source of O2, eventually.

 

[wedivebc]

Webdivedc -

Your argument really doesn't make any practical sense. You're ignoring the assumption the diver remains in charge thereby controlling the PO2. Just because you perform a Dil flush at any depth doesn't mean you're required to stick with the resulting PO2 for any portion of the dive.

If I'm holding a SP of 1.2 and flush at 66fsw my resulting PO2 will reduce to .63. Seconds after that flush the Hammerhead is going to start injecting oxygen to create a PO2 of 1.2 once again with no interaction from me whatsoever though I will probably have to blow off a little gas to maintain minimum loop volume.

If you're making a Dil flush prior to the ascent you're going to drop your PO2, but does breathing without oxygen injection. Clearly, oxygen injection, semi closed circuit mode, or bailout is required if you intend to surface once you've performed an Air-Dil Flush at depth. You have to have some source of O2, eventually.

At the risk of flogging this dead horse any more please understand the context of my post. It was stated that in the event of a failure that resulted in a hypoxic condition (electronics, gas supply, whatever) the diver could do a dil flush and surface. That, I maintain and any experienced CCR diver will agree is a bad course of action since in the absence of any oxygen supply for what ever reason a dil flush will only put you in a worse situation. The SOP by any thinking CCR diver would be to bail out to OC. If oxygen supply was available then a ,manual O2 flush would be in order once you reached 6m.
Using air as a SCR gas is equally stupid. Again the context that I was debating was the asinine claim that if Wes had been hypoxic a dil flush with air prior to ascent would have saved him.
Frankly I am tired of teaching RB 101 to muppets.

 

[Se7en]

If you flush with diluent you can then check your sensors and, depending on the the depth, the CCR will start adding oxygen; and you can watch the ppO2 in the loop rise. As far as Dalton's law is concerned, I've been teaching it longer than I expect you've been alive. You starting to grasp (or is it gasp) at straws with asinine insults and it does not become you. If you want to make this into a flame-fest ... go find another victim, I'm not interested.

If you flush and the unit starts adding O2, then the unit was working all along and you have achieved nothing by flushing.

If the unit isn't working correctly
(And for someone to die of hypoxia on a HH it needs the unit to not be working correctly)
Then flushing with a gas with PPO2 of .21 will probably kill you.

At 70 ft (24 metres), if you flush with air you will have a loop PPO2 of around 0.5 and an FO2 of .21
The loop (of an average rebreather at min loop) will have a volume of around 10 litres, meaning it is holding around 25 litres of air (surface equivalent)
With air in the loop, this means you have 5 litres of O2 and 20 litres of N2.
On ascent, as you are a bit busy, your body will be using about 1 litre of O2 per minute.

So what happens on ascent?
15 litres of your 25 litres is vented (as the loop has a 10 litre volume)
That leaves you with 2 litres of O2 and 8 litres of N2

If the ascent takes 2 minutes, you respire 2 litres of O2.
That leaves you with 0 litres of O2 and you are dead.

If the ascent takes you 1 minute, you respire 1 litre of O2.
That leaves you with 1 litre of O2, 8 litres of N2, and a PPO2 of .11. You are still dead.

These are trivial calculations that any CCR diver (should) know back to front.
ANY CCR that is not injecting O2 will kill you in a few minutes, rich dil only gives you an extra minute (maybe).

In my group of divers, the SOP for an unresponsive diver on the bottom is to inject as much O2 into their unit as you can until they are boyant and then let them go - to give them some chance of making the surface with a breathable loop. (There are 3 anesthesiasts and a Hyperbaric medicine specialist in the group I dive with).

Personally, my ascent procedure is to inject a good slug of O2 before leaving the bottom. Push the loop up to 1.6 ish. It is going to be dropping as you ascend, and the process of adding O2 gives me a chance to ensure everything is OK. I also don't trust the unit to inject on ascent and do it manually - I know that my unit CANNOT inject O2 fast enough via solenoid to keep up with an uncontrolled ascent from depth.

Mike

 

[flots am]

If the ascent takes 2 minutes, you respire 2 litres of O2.
That leaves you with 0 litres of O2 and you are dead.

If the ascent takes you 1 minute, you respire 1 litre of O2.
That leaves you with 1 litre of O2, 8 litres of N2, and a PPO2 of .11. You are still dead.

. . .

Personally, my ascent procedure is to inject a good slug of O2 before leaving the bottom. Push the loop up to 1.6 ish. It is going to be dropping as you ascend, and the process of adding O2 gives me a chance to ensure everything is OK. I also don't trust the unit to inject on ascent and do it manually - I know that my unit CANNOT inject O2 fast enough via solenoid to keep up with an uncontrolled ascent from depth.

Mike

That sounds like an awesome design.

I can hear the thundering herd of class-action attorneys from here.

flots.

 

[Se7en]

That sounds like an awesome design.

I can hear the thundering herd of class-action attorneys from here.

flots.

That attempted sledge is irrelevant to the discussion of why flushing with dil before leaving the bottom is a bad idea.
The maths on what happens to the PPO2 on ascent is true for any rebreather that is not adding O2 for you - it's not specific to the unit I dive as you have tried to imply.
(besides - there is no reason for a lawsuit as the rebreather in question has an excellent safety record over the 15 years it's been around.)

Anyway - I put the post up to show Thallassamania why flushing with dil before ascent is a bad idea - do you have anything to contribute on that subject?

Mike

 

[flots am]

Alex - bugger off.That attempted sledge is irrelevant to the discussion of why flushing with dil before leaving the bottom is a bad idea.The maths on what happens to the PPO2 on ascent is true for any rebreather that is not adding O2 for you - it's not specific to the unit I dive as you have tried to imply.(besides - there is no reason for a lawsuit as the rebreather in question has an excellent safety record over the 15 years it's been around.)I also happen to have a 'lifting the veil' rebreather in the garage as well - how do you think that'd go in an uncontrolled ascent? Without a solenoid I suspect it'd fair pretty poorly.Anyway - I put the post up to show Thallassamania why flushing with dil before ascent is a bad idea - do you have anything to contribute on that subject?Mike

Sure, I've noticed a significant number of posts that contain phrases similar to " . . . and the you die . . ." leading me to believe that rebrether technology isn't quite ready for "prime time".flots.

 

[Se7en]

Sure, I've noticed a significant number of posts that contain phrases similar to " . . . and the you die . . ." leading me to believe that rebrether technology isn't quite ready for "prime time".flots.

Drive along the road at 100 and take you hands off the wheel for a couple of minutes - and you will die.
Go a couple of hundred meters into a cave with a single tank and run out of gas - and you will die.
Lie face down in the bath and don't raise your head to breathe - and you will die.

Seems that cars, OC scuba and bathtubs are not ready for "prime time" either by that logic.

No ECCR manufacturer would suggest flushing with Dil before ascent, no experienced ECCR diver would do so. I was just explaining why.
The fact that you could kill yourself by using the tool incorrectly doesn't in any way imply that the tool "is not ready for prime time". Suggesting as much just implies trolling.

Mike