Decompression Tables

[rstofer]

Personally if divers took a more cautious approach to the tables, there would be far less accidents. It's not if you can do the dive, it's how long you need to decompress if you've gone over the NDT. With the global rate of injury and death resulting each year from DCS, isn't this something worthy of discussion? Just a thought...

Thanks for your answer.

Just exactly what is the incidence/severity rate? My impression is that it is small to non-existent among recreational divers. It's should be even less with the PADI recommended safety stop.

Richard

 

[Meng_Tze]

Each agency uses Decompression Tables based upon different models (as do the various computers). ACUC International uses the DCIEM Table which allows a maximum NDBT on the 1st dive to be a maximum of 15 minutes at 100 FSW. PADI Tables on the other hand allow 20 minutes. The U.S. Navy Tables (1993) allow 27 minutes and the French Navy Tables 30 minutes.

Personally if divers took a more cautious approach to the tables, there would be far less accidents. It's not if you can do the dive, it's how long you need to decompress if you've gone over the NDT. With the global rate of injury and death resulting each year from DCS, isn't this something worthy of discussion? Just a thought...

Thanks for your answer.

Not sure where this is going..............purpose?

 

[HenrikBP]

"Deco for Divers" by Mark Powell is current and quite readable.

It's on my B'day list already Thanks

Henrik

 

[Eric Sedletzky]

When I first started diving I used regular PADI rdp air table.
When I started tech diving we used V-planner
I have since given up tech diving but still employ deep stops into virtually every dive regardless of time (but not necessarily depth).
For a while I used a Suunto Vyper. Once when diving out on Farnsworth Bank off the coast of LA CA., I buudied up with a friend who was fully DIR trained and used a Buhlman model table. What ever they use? But I know it includes the 120 rule combined with deep stops starting at half the max depth. I decided I was going to follow my buddies profile and dive his table.
It was an air dive (I know, big DIR no-no) but anyway we avaraged 100 feet for around 20 minutes. some of the depth got to 120 for a minute or two and some at 80 feet for about the same time, average it at 100.
My Suunto freaked out and put me at 3 or 4 minutes over. We headed up at 30 fpm, stopped at 60 for a minute, my computer still showing negative, we went up to 50 for a few minutes, the computer began to add penalties. As the stops continued the computer kept adding negative time with a blinking arrow telling me to get my butt to 15 feet. By the time we completed all our stops and got to 15 feet my computer wanted me to stay there for 15 minutes or some rediculous amount of time. I had a watch and depth guage on anyway and was basically testing the unit to see what it would do when taken to the max, and the answer I got was that somebody not knowing about deep stops would have gone right to 15 feet like the computer said and maybe suffered a hit in their fast tissues.

Maybe computers have changed since then, but every one of the rec consumer models in the moderate price range available to the general public at that time gave short bottom times and a constant ascent rate to 15 feet with no credit for deep stops. I don't know what model that would be after, (Hill?
Maybe there are new ones now that people can program, I'm sure there are.
I'm happy using PADI tables, depth averaging, and always including deep stops. Maybe that's what the OP was talking about as far as fudge factor.
I'm no decompression guru by any means, I just fun dive, but it works for me.

Here's a good article I read once about the new thinking regarding decompression and deep stops.
DAN Divers Alert Network

 

[wedivebc]

I believe citizen made a dive computer incorporating DCIEM algorithm although I am told it is discontinued.
I use Gradient factor 30/85 on my pursuit and decosoft VPM at +5 on my liquivision

 

[vladimir]

With the global rate of injury and death resulting each year from DCS, isn't this something worthy of discussion? Just a thought...

I was under the impression that the global rate of injury and death from DCS is minimal. Am I misinformed? The few cases I have personally witnessed would have violated any decompression model. Perhaps it is different among "technical" divers.

 

[gcbryan]

Too many I'm afraid, including:
1. U.S. Navy Tables (Air)
2. U.S. Navy Tables (HeO2)
3. DCIEM Standard Air
4. DCIEM HeO2 to 100 metres
5. Meta Model experiments as a test diver at DCIEM
6. Oceaneering International (OI) Alpha tables
7. OI Yankee Bell Tables
8. SubSea SSM7 (modified Buhlmann) Bell Bounce Tables
9. SOSI Bell Bounce Tables to 200 metres
10. EBSDC (Component 2) Saturation to 400 meters
11. Meta Model experiments as a test diver at DCIEM
12. Others (When teaching SCUBA I use the Tables adopted by the training agency)

The main reason why there's such a large selection, is that it's up to each Commercial Operator to prescribe the Table to be used to meet the situation at-hand (liability). Also, different Tables were used at different times in my diving career.

When using a computer (recreational diving) I like the Liquivision X1 (VPM B, B/E, +2 conservatism)

It's a fair answer to a fair question but it's kind of beside the point in the context of this discussion regarding all the tables used in your commercial diving. I'm not trying to be a jerk I'm just trying to figure out what the point is?

 

[DCBC]

Just exactly what is the incidence/severity rate? My impression is that it is small to non-existent among recreational divers. It's should be even less with the PADI recommended safety stop.

Richard

As far as Diving Computers are concerned:

DCS
Dr. Richard Moon's paper "Evaluation of a Method for Reducing Decompression Sickness (DCS) during Recreational Diving" (2009) states that in a dataset provided by DAN, in 52,168 recreational air dives, there were 23 DCS incidents (using dive computers). That's approx. 1 incident of DCS in every 2200 dives for dives using a computer.

Given the total number of dives claimed by the members on this site, if this information is reliable, almost everyone will have experienced DCS at least once... I point this out because the the incidence rate is in-fact much higher than one might like to think.

AGE
The following is an abstract of a report published in the 2002 Undersea Hyperbaric Medicine Journal;29(4):247-259 regarding the incidence of venous gas emboli in recreational divers:
The Divers Alert Network monitored recreational divers for Doppler-detected venous gas emboli (VGE) and depth-time profiles following multi-day, repetitive, multi-level exposures. A Spencer score >0 occurred in 61 of 67 subjects (91%) and 205 of 281 dives (73%). No subject developed decompression sickness (DCS) on monitored days although 102 dives (36.3%) scored at Spencer Grades 2 or 3 (High Bubble Grade, HBG). We recorded the depth-time profiles with Suunto dive computers and estimated exposure severity with a probabilistic decompression algorithm. The HBG incidence increased 53% over the range of exposure severity (p<0.001) in the divers, was approximately 20% higher for repetitive dives than for first dives, and decreased approximately 25% over the 6-8 days of multi-day diving (p<0.001) suggesting a phenomenon similar to DCS adaptation. The observed HBG incidence was approximately 20% higher for males than females. Older male divers had a 25% increase in observed incidence of HBG while older female divers showed a 55% increase when compared to their younger counterparts.

In the Bova and Davis' manual on diving medicine Chapter 7, page 152 notes that for Type II DCS, the incidence is the smallest in Military Test and Commercial Divers with twice the number of incidents (per number of dives) by Recreational Divers.

 

[DCBC]

It's a fair answer to a fair question but it's kind of beside the point in the context of this discussion regarding all the tables used in your commercial diving. I'm not trying to be a jerk I'm just trying to figure out what the point is?

I merely wanted to answer his question. I originally posted my question to promote discussion and get people thinking more about why they were doing things the way they are. DCS is a real hazard. Many of us are diving deeper and as such the incidence of Type II DCS in recreational diving is increasing. Perhaps this is a good time to sit back and re-evaluate things...

 

[HowardE]

While the number of incidents has increased, so has the number of dives made. According to the DAN 2008 Report: It appears as though the overall DCS / 10,000 dives has gone down.