Safety stop : to do or not when panicked?

[KenGordon]

Assuming the air is plotted from A.I.? Curious, does it look weird to anyone that during the first 2mins of the dive the air usage during descent appears the same as bottom? wouldn't you expect this to ramp up during this time? or is that typical with colder dives? does it indicate discomfort/stress before the dive, slow leak even?

It seems a bit of a coincidence that the pressure line is linear (can you get it to plot SAC?) but in a drysuit and especially with big cylinders (although not really with an 80) the gas use on the descent for buoyancy can dwarf that for breathing.

You might need 8l of buoyancy to offset the mass of air in a twinset and say 4 in a drysuit. That is like a sac of 12l/10m of decent. So descend at 10m/min and you almost double the gas use rate.

Sounds to me like a typical 'don't get in the water' day, too much to drink, headache and generally being 'off' leads to mild apprehension before the dive which turns less mild with extra co2 and nitrogen. All the circular search stuff can eat time and attention.

Next time take more gas, work out how much is enough and go more slowly. Maybe pause at 20m to make sure you are happy.

Did you do much of a surface swim? Were you exerted on the boat? Sometimes the whole standing up and jumping in thing is such a hassle that you are already ****ed before you hit the water.

Try to be relaxed before you get in. Have 5 minutes completely kitted up and ready to go sat on the bench doing nothing. If people hassle you either get ready sooner or find nice people to dive with.

 

[Storker]

Assuming the air is plotted from A.I.? Curious, does it look weird to anyone that during the first 2mins of the dive the air usage during descent appears the same as bottom? wouldn't you expect this to ramp up during this time? or is that typical with colder dives? does it indicate discomfort/stress before the dive, slow leak even?

Some AI computers, like my Suunto Cobra, log only starting pressure and end pressure, and calculate your RMV based on those two numbers and your depth profile. Which means you don't get any info about the changes in gas consumption during the different phases of the dive, except for the effect of depth.

It might be that the OP's comp does the same.

 

[rongoodman]

Not sure I understand... are you saying to use trimix for a 105' dive?

I'm saying exactly that, at least for me on a cold dark dive such as the Radeau. Warm, clear water in the Caribbean is a different story. What's the point of paying the charter fee and not being able to remember most of what I saw?

 

[boulderjohn]

Not sure I understand... are you saying to use trimix for a 105' dive?

When I was diving as a UTD student, trimix was required below 100 feet.

 

[doctormike]

Wow, live and learn...

I have been diving for a long time in the NY/NJ area, and have never seen anyone use trimix in those ranges... But I guess there is a bell curve for everything!


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[boulderjohn]

Wow, live and learn...

I have been diving for a long time in the NY/NJ area, and have never seen anyone use trimix in those ranges... But I guess there is a bell curve for everything!

It is an interesting contrast between agency beliefs. With UTD (and I think GUE--not sure), we were required to use helium mixes on all dives below 100 feet. That means we were required to use it from the very first technical training dive of the program. With other agencies, you are prohibited from using helium in technical training until the divers have completed a number of certifications on (relatively) deep air or nitrox.

 

[doctormike]

It is an interesting contrast between agency beliefs. With UTD (and I think GUE--not sure), we were required to use helium mixes on all dives below 100 feet. That means we were required to use it from the very first technical training dive of the program. With other agencies, you are prohibited from using helium in technical training until the divers have completed a number of certifications on (relatively) deep air or nitrox.

That IS interesting, the two philosophies.... The debate is way above my pay grade, but I guess the response by non-UTD agencies to this question would be things like the TDI Extended Range (deep air) course.

When I did my tech training, my instructor made the point that a lot of what is considered nitrogen narcosis is actually CO2 retention, especially at depths where the majority of people would not have symptoms based on PPN2 alone. He felt that "recreational trimix" wasn't appropriate for that reason, and stressed techniques to limit hypercarbia.

Of course, when someone claims to have been narked at 90 feet, there is no way of proving that one way or the other, but based on my own experience at depths in the 120 foot range, I haven't noticed these symptoms. YMMV.

 

[boulderjohn]

I would just like to add something that puzzles me about this thread....

It seems to me that the question is asking for the proper, well-thought out procedure that a diver should follow while in a state of panic. I'm confused. The two situations seem to me to be contradictory.

 

[PfcAJ]

When I did my tech training, my instructor made the point that a lot of what is considered nitrogen narcosis is actually CO2 retention, especially at depths where the majority of people would not have symptoms based on PPN2 alone. He felt that "recreational trimix" wasn't appropriate for that reason, and stressed techniques to limit hypercarbia.

Of course, when someone claims to have been narked at 90 feet, there is no way of proving that one way or the other, but based on my own experience at depths in the 120 foot range, I haven't noticed these symptoms. YMMV.

CO2 is certainly a component of narcosis, along with nitrogen. Trying to isolate one from the other is pretty tough. Introducing helium reduces gas density and helps reduce co2 retention, and therefor narcosis (along with reducing the nitrogen component).

Not being narked and not noticing you're narked are two different things. Doing the same dive on air or nitrox then doing it on trimix is pretty eye opening.

 

[AJ]

That IS interesting, the two philosophies.... The debate is way above my pay grade, but I guess the response by non-UTD agencies to this question would be things like the TDI Extended Range (deep air) course.

It's a very strange debate. SSI tells me: you're fine to go to 40m/120ft on plain air with deep diver. GUE tells me: you should use Nitrox with a limit at 30m/90ft. Personally I restrict myself to the GUE standard. But still it's strange.

As far as the OP goes, I wonder if the AI was refelcting the right pressure? Although I have been diving with AI in the past, I always used an SPG for backup. I had some incidents where AI was not showing the right pressure. Finally I ditched it because of a short cut.