Which deco stop to skip?

[boulderjohn]

Kudos to the OP for beginning the discussion. The possibility of skipping planned stops was not part of my deco training, IIRC.

Even if you are going to be totally fastidious in your planning and will never have any problems of this nature, it makes a good discussion for training because to be able to come to a decision, you have to come to an understanding of decompression theory and the variety of plans that exist. It forces you to go beyond just writing down what the instructor tells you to do. You have to understand it and make decisions, which requires a much higher level of thinking than merely repeating what you were told.

 

[waterpirate]

The fellow who taught my Cavern and Intro classes also teaches technical diving. He uses a pure dissolved gas decompression strategy, and one deco gas . . . 100%. He has done this for years, and taught it, and he's not a pretzeled cripple yet. So, although I suspect this is not the best decompression routine you can use, I hold it in the back of my head as a way to get as shallow as possible, as quickly as possible. As the best diving instructor I ever had put it, "You can fix bent; you can't fix drowned."

Reading the proceedings of the DAN Symposium on technical diving, I was struck by the fact that there is no evidence at all that very deep stops are useful, and I believe (unpublished communication) that there are some research studies being done that suggest that decompression strategies utilizing very deep stops are resulting in higher bubble grades. And although bubble grade is not an adequate proxy for DCS, if the deep stops are DESIGNED to control bubble formation and they do not do it, then we are wasting deco time and gas doing them.

The bottom line is that no one knows what the best shape for deco is, or even in some cases how MUCH deco is sufficient, or ideal. We know that at least several different approaches result in uninjured divers. In a last ditch, desperate attempt to get out of the water (which is how I see the OP's question) I would get shallow and spend as much time there as I could. Yes, that's "abandoning" the deco model I prefer -- but I would have had to abandon many of the other principles by which I plan such dives, to end up in such a bind.

This was how it was explained to me. an almost mirror of what is said above. " if you are truly FUBAR, you need to get as shallow as you can, with the remaining gas you have, and salvage whatever you can, from a plan." I also have come to view my puter as a tool to hopefully be used by my saviours to at least have a record of what I did, in case I can not tell them myself, how I had to modify a plan to prevent drowning.
Eric

 

[rjack321]

The possibility of skipping planned stops was not part of my deco training, IIRC.

I was "taught" similarly to the OP, "do the deeper stops" because those control the CNS tissues. Which is possibly true, to a limited degree. But I've never seen any evidence that it works when you have to truncate a deco schedule (something I've never had to do)