Deep diving accident

[Steve R]

Right bottom is *average* 1.2 with max of 1.4 allowed.

Also, I think all deco bottles (except O2) are equal to approx 1.2 average PPO2 (1.6 when you switch but I think when you average in the shallower stops -- certainly for the 50% bottle -- it's about 1.2 not 1.6)

I'm thinking you're the only one talking averages........

I can average 0.95 on O2, but attempt to start it at 3.0

 

[limeyx]

I'm thinking you're the only one talking averages........

I can average 0.95 on O2, but attempt to start it at 3.0

I do not think I am the only one talking averages.
This is generally so with GUE (Average depth, average PPO2)
Note the rest of my statement *average 1.2 max 1.4*
so if you do a lot of time at 1.4 then you need to do a lot of time less than 1.4 ..

For longer/more aggressive dives, GUE recommends to drop the PPo2 even more, maybe even less than 1.0 for the working portion (the 1.2 is a "maximum" not necessarily and endorsement)

I have taken to diving 18/45 in the 130-200 range partly for these reasons, and essentially skip 21/35 altogether.

 

[padiscubapro]

Don't know, that's what I remember, and now after dinner I'm way too lazy to look it up. Or ask padiscubapro, Joe's knows the correct value to the 5 digit past the comma.

depends on the diver's certification level and the enviroment.. a l3+l4 diver is 4.5pn2 for a non overhead dive.. 4.0 is for recreational and hard overhead enviroments..

the allowable pn2 for a mix with trimix in it, is either 3.2, 3.6 or 4.0 depending on the certification.

There is talkto lower the tsd/erd depths to 44.5m to lower the max pn2 to 4.0

 

[padiscubapro]

If, in fact, this was an O2 hit at 15 feet, it will be at least the second oxtox event this year to occur at what are normally considered acceptable ppO2s, and it may be the third. The other two died. I'm beginning to think GUE's conservativism on ppO2s may be completely justified.

po2 liimits are alot lower than they were ni the past..

When I started diving with nitrox we were using 1.6 (or more on deep dives) as a BOTTOM gas and up to 1.8/1.9 as a deco gas without any ill effects.. The sample portion is much smaller than it was then. but there were rarely any otox cases that we heard of (and it was always shallow on o2).. This all started changing once people started diving gases with helium.. It seemed the number of cases rose and there is some anececdotal evidence that helium in the breathing gas raises the risk for otox..

 

[DA Aquamaster]

po2 liimits are alot lower than they were n the past..

When I started diving with nitrox we were using 1.6 (or more on deep dives) as a BOTTOM gas and up to 1.8/1.9 as a deco gas without any ill effects.. The sample portion is much maller than it was then. but there were rarely any otox cases that we heard of.. This all started changing once people started diving gases with helium.. It seemed the number of cases rose nd there is some anececdotal evidence that helium in the breathing gas raises the risk for otox..

That makes sense, except it may not be the presence of helium but rather the reduced amount of nitrogen in the mix. I know at one point the discussion centered on the role that nitrogen has in suppressing ox tox effects - roughly similar to the advantages of adding a small percentage of of nitrogen back into the heliox mix for deep saturation divers who would otherwise be at elvated risk of HPNS.

 

[z3r0c00l]

When I started diving with nitrox we were using 1.6 (or more on deep dives) as a BOTTOM gas and up to 1.8/1.9 as a deco gas without any ill effects..

There never are any ill effects until you drown, isnt that the danger of O2? : )

 

[VooDooGasMan]

The only Ill effects I 've experienced is when I deco on neon, I take a blow nozzel and plug it in my argon drysuit line and take a couple shots. It take the fuzzyness out of my vision, kinda levels out the Ill effects.

 

[z3r0c00l]

Breathe some N2O while you are at it, take the edge off : )

 

[padiscubapro]

That makes sense, except it may not be the presence of helium but rather the reduced amount of nitrogen in the mix. I know at one point the discussion centered on the role that nitrogen has in suppressing ox tox effects - roughly similar to the advantages of adding a small percentage of of nitrogen back into the heliox mix for deep saturation divers who would otherwise be at elvated risk of HPNS.

its probably a combination of both.. n2 is a strong cns depressent, but He appears to have more of an effect than just the n2 it replaces..

 

[padiscubapro]

There never are any ill effects until you drown, isnt that the danger of O2? : )

SO far I have not heard of a case where a HEALTHY person diving within the normal limits has had a seizure.. All the cases I have heard either the person had a past history of seizures (manyin the distant past) or had an undiagnosed conditon that was discovered afterwards.. The elevated o2 triggered an existing condition.. As the use of Nitrox grows people that never had problems might have had problems due to other medical conditions..

O2 tolerance varies from day to day, but all the measureable changes are well outside the normal accepted ranges..