Reverse profiles why 12m?

[Mantra]

Hi all,

When diving reverse profiles, the recommendation from DAN et al based on the 1999 conference is for there being no more than a 12m difference between depths is given.

I’m wondering if anyone knows why this figure specifically is given? If the first dive is a longer shallow one in say 6-10m of water, what is the argument for limiting the next dive to 22m? Can a dive computer not be trusted to monitor saturation on a shorter multilevel second dive to say 30m then 20m then 10m?

Just trying to get my head around this specific recommendation as it became relevant for me today when planning some dives with my buddy.

Thanks!

 

[tursiops]

If you look at the proceedings of that 1999 conference, that point was argued about. The final recommendation was on the conservative side, since there was so little data with reverse profiles to show larger depth excursions might be OK. I'm comfortable ignoring the 12m restriction given that we've now had 18 years of experience with few if any problems. The biggest problem with reverse profiles is that it is horrible N2 management.

 

[Mantra]

If you look at the proceedings of that 1999 conference, that point was argued about. The final recommendation was on the conservative side, since there was so little data with reverse profiles to show larger depth excursions might be OK. I'm comfortable ignoring the 12m restriction given that we've now had 18 years of experience with few if any problems. The biggest problem with reverse profiles is that it is horrible N2 management.

Thanks for that. I’ve been a little bent (underserved hit - but multi day diving riding the NDL and probably dehydrated) once before so try to err on the cautious side. Good to know it was more a rule of thumb. I would lean towards trust my computer and stay well outside the NDL as it’s set to conservative anyway. I think I will also read deco for divers again as a refresher and those proceedings. Thanks!