Deep Stops Increases DCS

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Status
Not open for further replies.

Kevrumbo

Banned
Messages
5,659
Reaction score
1,369
Location
South Santa Monica Bay/Los Angeles California, USA
# of dives
1000 - 2499
Look at the Bottom Mix Gas used in the NEDU Study link above (essentially Deep Air):
(Abstract, p.i). . .Divers wearing swimsuits and tshirts, breathing surface-supplied air via MK 20 UBA, and immersed in 86 °F water were compressed at 57 fsw/min to 170 fsw for a 30 minute bottom time during which they performed 130 watt cycle ergometer work. . . Results indicate that slower tissue gas washout or continued gas uptake offsets the benefits of reduced bubble growth at deep stops. . .
(Conclusion p.18) . . .The practical conclusion of this study is that controlling bubble formation in fast compartments with deep stops is unwarranted for air decompression dives.
This is the simple main practical point IMO/IME, to take away from the study:

Of course you're going to have significant residual inert Nitrogen and potentially on-gas N2 at your deep stop & perhaps even possibly at intermediate deco stops on Eanx50 which may encroach on critical slow tissue M-values as well --if you were using a working bottom mix with a high fractional N2 content to begin with like Air. Plan accordingly, use a computer to track your inert tissue loading (i.g. Shearwater Petrel) and be prepared to extend your 6m depth 100% Oxygen deco profile along with a stand-by IWR contingency protocol.
 
Last edited:

tomfcrist

Contributor
Scuba Instructor
Messages
2,895
Reaction score
1,817
Location
Virginia, USA
# of dives
I'm a Fish!
The profile was rediculous. 170/30minutes would give me 74 minutes of deco without deco gasses. That's 104 minutes vice 174. What the hell were they doing for the other 70 minutes?
 
OP
D

Divetech99

Contributor
Messages
232
Reaction score
19
The profile was rediculous. 170/30minutes would give me 74 minutes of deco without deco gasses. That's 104 minutes vice 174. What the hell were they doing for the other 70 minutes?

Yes, you're right. looks like their deco time was longer than normal deco time. Why? What model were they following or testing?
 

rjack321

ScubaBoard Supporter
ScubaBoard Supporter
Messages
11,971
Reaction score
7,180
Location
Port Orchard, Washington State
# of dives
1000 - 2499
Yes, you're right. looks like their deco time was longer than normal deco time. Why? What model were they following or testing?

Two Navy models. Basically the conclusion was for any given deco time you cannot substitute time at say 50ft in lieu of time at 30ft without increasing your DCS risk. Assuming backgas (air) deco. No great surprise there.

They did not test the effect of for instance doing more time at 70ft after switching to EAN50 and then doing less time at 30ft on EAN50 before switching to O2.

Its only so so relevant to how OC divers do deco with gas switches. Read the long winded RBW thread and Simon Mitchell's and Dr. Doublette's Q&A if you want more info on what they tested and why.
 

LiteHedded

Contributor
Messages
4,079
Reaction score
947
Location
Orlando, FL
Gue has changed some of what they're teaching based on studies like these. David was just down speaking at the gue conference. Would have been a good time to ask him about their study
 
OP
D

Divetech99

Contributor
Messages
232
Reaction score
19
It would be interesting to know how GUE and UTD will change (or not change) their Ratio Deco and Min Deco procedures. Can we get David to share?

---------- Post added December 10th, 2014 at 11:44 AM ----------

A separate question. Dive computers have the feature to turn on the Deep Stop mode and set it for 1 or 2 minutes. I assume that these are not arbitrary deep stops but built into their decompression algorithm. Given this, what is the group's recommendation? Turn on deep stop in the dive computer or turn it off?
 
  • Like
Reactions: Jax

Kevrumbo

Banned
Messages
5,659
Reaction score
1,369
Location
South Santa Monica Bay/Los Angeles California, USA
# of dives
1000 - 2499
It would be interesting to know how GUE and UTD will change (or not change) their Ratio Deco and Min Deco procedures. Can we get David to share?

---------- Post added December 10th, 2014 at 11:44 AM ----------

A separate question. Dive computers have the feature to turn on the Deep Stop mode and set it for 1 or 2 minutes. I assume that these are not arbitrary deep stops but built into their decompression algorithm. Given this, what is the group's recommendation? Turn on deep stop in the dive computer or turn it off?
Again:

Look at the Bottom Mix Gas used in the NEDU Study (essentially Deep Air):
(Abstract, p.i). . .Divers wearing swimsuits and tshirts, breathing surface-supplied air via MK 20 UBA, and immersed in 86 °F water were compressed at 57 fsw/min to 170 fsw for a 30 minute bottom time during which they performed 130 watt cycle ergometer work. . . Results indicate that slower tissue gas washout or continued gas uptake offsets the benefits of reduced bubble growth at deep stops. . .

(Conclusion p.18) . . .The practical conclusion of this study is that controlling bubble formation in fast compartments with deep stops is unwarranted for air decompression dives.
Why do you think this will affect Deep Stops in Ratio Deco? Correct application requires the use of standard Helium mixes with Eanx50 & O2 deco for this particular depth: IOW, the study's parameters and conclusion above does not apply. . .
 
Last edited:
Status
Not open for further replies.
https://www.shearwater.com/products/teric/
http://cavediveflorida.com/Rum_House.htm

Top Bottom