Virginian diver dead at 190 feet - Roaring River State Park, Missouri

[Hiszpan]

That's a practice left over from old aladins and similar computers where you could not change conservatism, but you could change your mix. It should have died out in the 80-s or 90-s but somehow people keep doing it.
And on a rebreather that is constantly analysing the gas you are breathing does absolutely nothing.

Irrelevant for discussion about this incident but the practice of diving Nitrox but setting computer as air (provided depth is not curtailing factor - high pO2) is defensible.

Conservatism level means not much on a computer with no gradient factors. I had/have Cochran Commander where conservatism can be set 0-50 but what does it mean? What is 0 and what is 50? Ambiguous.
When I look at tables and I can see a difference in deco between 21% and 27% Nx for the same depth and duration, I can assess the magnitude of that difference to give me an idea how much conservatism I am opting for. After all, computers are just fancy calculators (talking about recreational diving’s use.)

 

[ChuckP]

All this reading but still the question of did he really tox? Why did it happen so fast and what happened? A PO2 graph from his computer would really be nice to see...........

I just try to wrap my head around what flipped a switch and caused a panic at 190'.....

 

[steinbil]

I just try to wrap my head around what flipped a switch and caused a panic at 190'.....

Being narced out of his mind and seeing the ppo2 spiking on his controller?

 

[crofrog]

None of what you said changes the fact that no, using standard gases would not insulate you from what happened. There is NO gas choice methodology that would have lead to a choice of using the gas he used on the dive he intended to do.

He did the dive using a gas that he (I believe) knew was not the right choice for that dive. Once a diver makes a conscious decision to use a gas that he knows to be not the right (or even a good) choice for the dive, how would a different methodology for choosing his gas insulate him from the risk? He CHOSE to take the risk of knowingly diving a (very) suboptimal gas.

If you're going to say that using standard gases automatically implies choosing the correct gas for the dive, well, then so does any other extant, accepted method of deciding on gases. Standard gases have no advantage there. Implying that "best mix" does not take into account ANY other factor other than the planned max depth for a specific dive is well, I feel like it is disingenuous, at best. Or maybe naïve, if that's REALLY what you think it means to choose the best mix for a dive? As I was taught, best mix for a dive does include calculating an FO2 and FHe, but those are the just starting numbers. They are not set in stone. Every other aspect of the dive can influence the final numbers chosen - including team logistics, contingencies, and other things.

You're not looking at how standard gases fit into the overall safety system, how they can be used to remove pressure from the divers to do the dive without the right gases, and how they can enable other members of the group to speak up when they see something they view as unsafe happening.

By choosing to dive standardized gasses the team is agreeing before the "heat of the moment" on what is an acceptable pp02, END, maximum allowable gas density, and other considerations that go into gas selection.

If he'd had been diving standardized gasses and using a team approach to diving the conversation on the pre-dive checks could have gone something like this.

We're planning a dive to 190ft and the standard gas chosen by the team for this dive as dilout is 15/55. This could have enabled the deceased to speak up and say that he only had a tank of nx26 right then and there and he was outside of the safety parameters discussed by the team beforehand and prevented this incident, or if he choose to continue the dive during in water checks he would have shown his team his gas analysis sticker during the bubble check, and then during the pressure checks reported to his team his pressure and gas selection. This would have enabled the team to say something like. I'm not comfortable doing this dive with you on Nx26 when you should have 15/55.

To summarize, some of the benefits of standard gasses are:

• The gas selection parameters are chosen beforehand, not when you're dealing with logistical or cost issues and avoids debates around acceptable risk once people have already invested considerable time and money and feel external pressures to complete the dive
• Simplifies project logistics
• Enables the diver to have SOPs to fall back on when making decisions that might compromise safety
• Enables the team to have SOPs to fall back on when someone is committing unsafe acts.
  

 

[rjack321]

Being narced out of his mind and seeing the ppo2 spiking on his controller?

Plus if you're narced and you've been pushing one of your dual MAV buttons and your ppO2 is not dropping at all then you switch to the other button and push that - between the two buttons you have definitely added O2 and made the ppO2 situation much worse than the EAN24 would have alone.

 

[ChuckP]

Plus if you're narced and you've been pushing one of your dual MAV buttons and your ppO2 is not dropping at all then you switch to the other button and push that - between the two buttons you have definitely added O2 and made the ppO2 situation much worse than the EAN24 would have alone.

Exactly - that is why it would be interesting to see the PO2 graph.

My understanding of toxing is a lights out situation, no awareness for the person that actually toxed. Convulsions are apparent to the people watching though - I hear this from commercial divers whom have dry toxed in chambers.

Narcosis is generally much mellower, slowed down reactions.

So again for the physiology or medical part of it - did he really tox or did he panic? The graph of his PO2 levels with depth would be beautiful to look at and better understand. If it really was a tox, was this reaction he had equally about OTU's combined with a spike in PO2? Or was it just pure panic with the haze clearing enough to notice the problem? The report states that his PO2 was only above 1.6 for a few minutes.......

I say this all and question this all because of one specific dive we do here in Mexico; your PO2 will be above 1.4 for just over 2 minutes and spikes about 1.57 (that is stats from one dive). This is a slightly deeper than normal dive with just the one point reaching a depth of really no more than 130' - we do this dive on 32% and of course OC. Are we really cutting this dive that close?

 

[Hiszpan]

Are we really cutting this dive that close?

Nobody can guarantee to you that you are or you are not. It is like with partial pressure blending without oxy cleaning your tanks or valves - some do it like that and get away with it. You can do it, too and get away with it. Still, you indeed would feel like an idiot in the last split second before the explosion tears you apart if one day the odds stacked against you (I am misquoting from the oxygen cleaning book, I did no invent the comparison myself, but I think it summarizes normalization of deviance accurately.)

 

[inquis]

@ChuckP NOAA has said the maximum exposure to 1.6 ata O2 is 45 minutes. There is a correlation with oxtox & CO2 retention, so minimize your effort in order to avoid that.

We don't know the ppO2 history for this incident, so I do not wish to draw any conclusions based on it.

 

[Kay Dee]

My understanding of toxing is a lights out situation, no awareness for the person that actually toxed. Convulsions are apparent to the people watching though - I hear this from commercial divers whom have dry toxed in chambers.

In the 2nd of the two OC oxtox events I witnessed (this one whilst on deco) the person had enough warning to remove the reg and switch to a lower ppo2 mix while also having the wherewithall to ascend several meters to further reduce the ppo2. The first (at depth, with an astronomical ppo2) seemingly had no warning, and drowned.

 

[Johnnycannuk]

Exactly - that is why it would be interesting to see the PO2 graph.

My understanding of toxing is a lights out situation, no awareness for the person that actually toxed. Convulsions are apparent to the people watching though - I hear this from commercial divers whom have dry toxed in chambers.

Narcosis is generally much mellower, slowed down reactions.

So again for the physiology or medical part of it - did he really tox or did he panic? The graph of his PO2 levels with depth would be beautiful to look at and better understand. If it really was a tox, was this reaction he had equally about OTU's combined with a spike in PO2? Or was it just pure panic with the haze clearing enough to notice the problem? The report states that his PO2 was only above 1.6 for a few minutes.......

I say this all and question this all because of one specific dive we do here in Mexico; your PO2 will be above 1.4 for just over 2 minutes and spikes about 1.57 (that is stats from one dive). This is a slightly deeper than normal dive with just the one point reaching a depth of really no more than 130' - we do this dive on 32% and of course OC. Are we really cutting this dive that close?

My understanding from the news reports and the NSS-CDS report was he was in panic trying to ascend then toxed (he was seen going into convulsions). Given the mix, the fact he was doing work, and was narked, its possible a combination of a CO2 hit and narking got him panicked when he say a O2 spike, he then instinctively did a dil flush (which would not work at all at that depth with that mix, it would make it worse). He may have been exposed to 1.8 for longer than a few minutes. We don't know where his OTU were at before the dive if this was a number of dive days in a row. And different people react differently, physiologically. Gus had a similar incident and didn't tox.

So I am pretty certain he toxed, the question is why - why so (relatively) quickly? I think its a forgone conclusion here that he was using the wrong gas for the depth.