Dive planning and OTU's

[jj1987]

I worry more about CNS loading than OTU.

To reduce CNS load, made your last stop at 10' rather than 20' where the cave allows.

Some cases, dial down the ppo2. 30% in ginnie Starts to load your CNS for long dives.

Just curious, why are you concerned about CNS? Personally I don't really pay attention to that.

[bamafan]

Not always in habitats, especially not lately.

Low ppo2s on the bottom and gas breaks seems to be successful.

I asked this same question about what the WKPP was doing during my Trimix class and this is what my instructor told me. A buddy and I were discussing this subject this weekend and I thought that was what was being done. I guess it is about like anything else in cave diving as it is a risk / rewards scenario that we all have to decide what to do.

[Kevin Leonhardt]

I was taught that for every 20 minutes on O2 you are supposed to take a 5 minute "air" break. I always do this but I can not find any research where this would allow you to exceed 100% of your CNS clock. I have run numerous scenarios of a 4 hour dive at 90' on V Planner and unless I want some extreme deco I can't get the CNS % below 100%. What are others doing on dives like this?

Attachment 11440

That dive is clearly impossible to do, just pick something easier.

Seriously, 30% on the bottom, 100% at 20', and 5min breaks every 15min is the way I do it.

[nakatomi]

Just curious, why are you concerned about CNS? Personally I don't really pay attention to that.

He is concerned because he doesn't want to tox in the cavern and become fish food.

[bamafan]

He is concerned because he doesn't want to tox in the cavern and become fish food.

There are probably some who wish I would. My girlfriend is one of them right now as I keep going cave diving to much.

[bamafan]

That dive is clearly impossible to do, just pick something easier.

Seriously, 30% on the bottom, 100% at 20', and 5min breaks every 15min is the way I do it.

I know it is just a basic cave dive for you Kevin. I do appreciate your advice and enjoyed meeting you at JB a few weeks ago.

Eric

[firemedic1015]

There is a discussion over on CCRX about a presentation made by Dr. Simon Mitchell at EUROTEK regarding CNS exposures. I'll apologize in advance for the cross forum posting but it appears that the discussion on CCRX is the only place the information is currently available online. It's supposed to be published in the near future. It can be found here

As far as pulmonary toxicity goes the NOAA-REPEX table, ie. OTU's, listed in the article linked by Bamafan seems to still be the standard. 850 OTU's for a fresh diver and leveling at 300 by day 11. Even day one has enough OTU's reserved for a chamber ride. If your not planning to get bent you could go significantly beyond 850 on day one

[nakatomi]

Thank you for providing us with that link, that is very useful information!

[bamafan]

Thanks for the link. I agree with Oliver it was very interesting.

[patpicos]

Just curious, why are you concerned about CNS? Personally I don't really pay attention to that.

Hi James

Assuming hitting 100% CNS Clock on a single dive is dangerous and that it will kill you if you breach it (over-reacting on this one), I find it much easier to hit the CNS clock limits for my dives versus getting anywhere close to reaching OTU limits. I try to stay below 80% and its often fairly easy to do so w/ the standard gas being pumped in Cave Country and doing my last stop at 10'
Typical cave diving day for me is doing a single dive in the 100-110min range. Rarely doing 2 dives if doing that long w/ deco. I will do 2 90min dives at Peacock on the other hand..

Now, to air breaks..ive learnt the hard way on my last dive where I chose to skip the air break and tough out O2 for 27mins since my buddy was a jerk laughing at me since he cleared 15mins earlier than I did. On the surface, I had an unpleasant dry cough for a few minutes. Perhaps it is time to change my 25/75 GF on petrel