How Much Deco Can you Blow Off?

[ianr33]

Came up in another thread.

I know this is one of those unanswerable questions,but, just for discussion:

How much deco can you miss and still have a chance of no major ill affects? To put some boundaries on it, lets suppose the dive was planned using V Planner +2 , 30/85 gradient factors or similar and the missed deco was on O2. Also lets only consider "normal" dives. Skipping the last 10 minutes of deco when you've already done 10 hours of it in Wakulla probably doesn't matter too much !

My personal, WAG is that if its my lucky day then I might be able to miss 10 minutes of O2 deco and be none the worse for it. Miss 30 minutes though and I would expect my diving career to be over.

Thoughts?

 

[Doc Intrepid]

I expect that data might show one answer would be "variable". IOW, it might not hit you one time, but the next time, same profile, you may get bent.

Other factors might include physical exertion/high workload during dive; fatigue; whether you were stressed during dive (elevated respiratory rates); alcohol consumption the night before/relative hydration; RNT from previous dives; surface interval prior to dive; temperature of water (e.g. very cold dark ocean v. warm tropical ocean); whether you've been bent previously and how badly; whether you've had surgery or internal damage to joints, etc.; general physical condition; and so forth.

One thing that we've done, though, when weather or wave heights looked like they might cut short our 10' hangtimes, is to add additional deco time at deeper stops to smooth out the curve and add the rest to the 20' stop - in effect cutting out the 10' stop altogether. We found it easier to peg a 20' stop in 3'-5' swells than a 10' stop, and it seemed safer that way. But thats not the same as simply "blowing the deco off".

As you said, probably unanswerable with any precision - its going to vary for different divers, and for the same diver among different dives. Deco is imperfectly understood...

As someone else mentioned, the thing I would be concerned with regarding missed deco is the possibility of winding up in a wheelchair. Not everyone comes back all the way....

 

[sea2summit]

Define no "major" ill effects.

I have a buddy who recently skipped some deco after blowing a dive plan and was lucky to get minor bends cured with one trip to the chamber. I've always kind of figured if both my computers fail and I don't have tables for what I got myself into I'm going to sit at 15' until I'm out of gas surface and if I'm okay immediatly sell all my gear for $1 because that was my one "give me".

I don't know if this thread will really have any value because just talking it over might insite some to try and skip "some" deco because some wise guy is going to post they always leave the 10' stop 5 min early, never breath O2 but replace it with 50 to save $, or someother foolishness.

Just plan the dive, dive the plan.

 

[ianr33]

Just plan the dive, dive the plan.

Normally,yes of course.

But,the original thread that made me ask was talking about surfacing with an unconscious buddy. I hope to never be in that situation ,but, if I am would like to have some idea if surfacing X minutes early is likely to have no lasting effects or will put me in a wheelchair before I decide what to do.

 

[sea2summit]

Normally,yes of course.

But,the original thread that made me ask was talking about surfacing with an unconscious buddy. I hope to never be in that situation ,but, if I am would like to have some idea if surfacing X minutes early is likely to have no lasting effects or will put me in a wheelchair before I decide what to do.

Ahh, that makes more sense. Let me see if I can meaningfully contribute with what I was tought for missed deco protocol:

No symptoms return to missed stop do all stops below 40' as scheduled, above 40' multiply stops by 1.5 and if my computer wants me to do more I’d do more. I'd probably hang out at 10 or 20 breathing O2 for an "extra" safety stop as well. Symptomatic I'd hang out as long as I could.

If your are already bent it's kind of one of those moments you have to decide based on youre buddies and conditions if you can/should return to the water, probably better to head to the chamber immediately.

 

[lobstah]

Some portions of deco are more crucial than others. 10 minutes of deco at 20 feet is something I would feel comfortable to risk. Any Type I would be fixed with O2 or a chamber, but removing 10 minutes at 120-80 range would have me seriously worried about Type II.

 

[Tortuga68]

Symptomatic I'd hang out as long as I could

10 minutes of deco at 20 feet is something I would feel comfortable to risk. Any Type I would be fixed with O2 or a chamber, but removing 10 minutes at 120-80 range would have me seriously worried about Type II.

What do you base this on?

 

[Diver0001]

Thoughts?

I would feel uncomfortable blowing off any of the deco we needed to do..... not even so much because of the risk of getting bent but more because of the number of preceeding mistakes that would be necessary to get myself in that situation to begin with.

The fact is, I've never given this much thought. My contingeny plans are all aimed at avoiding this.

R..

 

[Tortuga68]

Diver0001 the question, as explained further in a later post (#4), is about bringing an unconcious buddy to the surface

 

[Diver0001]

Diver0001 the question, as explained further in a later post (#4), is about bringing an unconcious buddy to the surface

Oh.

In that case never mind. If the only thing between the life and death of my buddy was my willingness to surface with a few minutes missed deco then I know what I would do.

I know people tell you never to become a 2nd victim ... so call me a bad rescue diver ... I'd rather get bent than have to deal with the guilt and regret of letting my buddy die because I was afraid of getting hurt saving him.

R..