Saturday, September 19, 2020
  • Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 43,000+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 510,000+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,450+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

decompression tables

Bill

Baron of Breathold
Oct 17, 2001
1,805
332
188
81
Kona
kv6j.net
We're trying to do a little work at 70 meters with the scooter. Does anyone know what the latest decompression tables for free diving say.
 

Nathan Vinski

Well-Known Member
Apr 19, 2015
247
146
58
24
Canada
The AIDA standards say to not dive at all for the rest of the day if you have done a dive deeper than 55-60m. This includes shallow and safety dives although in my experience and opinion almost everyone would be fine doing shallow safeties (<25m) . For some this could be an overly conservative recommendation and for others who are more succepttable to DCS could save their lives. When you say work at 70 with a scooter I'm assuming there is a task to be completed requiring bottom time (i.e. Changing a mooring or something like that??) which would mean absolutely not doing that depth more than once per diver. Some people may say that it would be fine and that they've done repeats in the 70s but if you look at Will Trubridge's recent accident it would be like playing Russian roulette.

In theory it would be possible to do these dives safely by doing them on exhale and limiting N2 exposure, or by doing O2 decompressions after each dive with a very long surface interval. (We don't know enough to recommend that interval).
 
  • Like
Reactions: zazuge and FraDive
OP
OP
Bill

Bill

Baron of Breathold
Oct 17, 2001
1,805
332
188
81
Kona
kv6j.net
The AIDA standards say to not dive at all for the rest of the day if you have done a dive deeper than 55-60m. This includes shallow and safety dives although in my experience and opinion almost everyone would be fine doing shallow safeties (<25m) . For some this could be an overly conservative recommendation and for others who are more succepttable to DCS could save their lives. When you say work at 70 with a scooter I'm assuming there is a task to be completed requiring bottom time (i.e. Changing a mooring or something like that??) which would mean absolutely not doing that depth more than once per diver. Some people may say that it would be fine and that they've done repeats in the 70s but if you look at Will Trubridge's recent accident it would be like playing Russian roulette.

In theory it would be possible to do these dives safely by doing them on exhale and limiting N2 exposure, or by doing O2 decompressions after each dive with a very long surface interval. (We don't know enough to recommend that interval).
 
OP
OP
Bill

Bill

Baron of Breathold
Oct 17, 2001
1,805
332
188
81
Kona
kv6j.net
Thanks for the input. I am hoping that there are some updated tables/rules. When I became a senior citizen, I started doing two 60-70 dives about thirty minutes apart. The spearfishing group has divers that slowly built up to five variables with hangs at 50. There is something that AIDA and DAN don't understand. Hopefully, someone is doing a practical evaluation. We had the same thing happen with flying after diving about fifty years ago but it all boiled down to the fact that if you are bent, flying will make the problem worse.
 

Nathan Vinski

Well-Known Member
Apr 19, 2015
247
146
58
24
Canada
I agree they need some updates and further research into DCS and freediving. The issue is that there a so many variables like ascent rate, temperature, lung volume, lung volume to blood volume ratio, fitness, hydration, alveoli wall thickness...

I recently started diving primarily on frc and I was surprised to find that there was a lack of narcosis in the 30-40m range on frc. I never noticed this when I only did inhale dives to those depths but now that I have a comparison I can feel a slight drunk-buzz at that depth. This shows that even at shallow depths there is a significant absorbsion of N2. Coupled with high ascent rates we are probably exposed to extremely mild DCS very often while freediving. I personally noticed much less fatigue after performing 35m repeats on FRC vs inhale which I'm assuming is related to N2 since pool work doesn't cause the fatigue either.

In my opinion the current tables are too leaniant as is allowing o2 deco after comp dives. If you can't safely survive a dive without intervention, you shouldn't do it.
 

cdavis

Well-Known Member
Jan 21, 2003
3,961
749
218
70
Sarasota, Fla
exhale diving to 7o m is possible, but would take a heck of a fexible chest. If you could do it, I'm pretty sure it would work to reduce DCS. My experiance with clear headedness that appears to be less narcosis at 25-30 meters (while diving 1/2 lung) matches Nathan's observations. Efattah had similar observations. I never noticed it either until I started diving exhale.
 
  • Like
Reactions: Bill
Mar 20, 2011
704
150
83
Los Angeles
Bill, did you ever find tables? There is some research being done on this but it is such a small segment that does these kind of dives, and from what I heard the deep freedive table was rather complicated.

One thing I have sometimes done when diving outside recommendations during training is deco hangs with nitrox at the end of a session, do a breathe up on the tank then FIM down to 10M, hang for a bit, then hand over hand ultra slow to the surface for a total dive time of 3+ min.

I know some variable spearos who will breathe pure O2 at 5M for 10 minutes after a session.

I have never been badly bent and doing the deco hang doesn't seem to make much difference in the way I feel but I do it anyway sometimes.

The one or two times I think I had mild DCS were a long time ago, spearing, and I have since changed ascent rates (now a little slower than 1 m/sec in the last 10M) and been fine even on far more aggressive days than I ever used to do. I rarely ever do variable or scooter.

Sent from my SM-G930T using Tapatalk
 
  • Like
Reactions: zazuge
DeeperBlue.com - The Worlds Largest Community Dedicated To Freediving, Scuba Diving and Spearfishing

ABOUT US

ISSN 1469-865X | Copyright © 1996 - 2020 deeperblue.net limited.

DeeperBlue.com is the World's Largest Community dedicated to Freediving, Scuba Diving, Spearfishing and Diving Travel.

We've been dedicated to bringing you the freshest news, features and discussions from around the underwater world since 1996.

ADVERT