Bent. I guess it really can happen to me.

[chillyinCanada]

Me thinks you don't understand how diving works if you think you can determine whether he should be bent from the info given. You have been given a max depth and the dive time, that's it. You don't know how long he was at that max depth. He could have been at 55' for 3 minutes and spent the remainder of the dive at 23'.

And that's why I've been asking for more detail.

 

[rivers]

I just ran this on baltic deco with a 20/85 GF as a square profile with a depth of 16m. It gave me 3 deco stops starting at 12m for one minute each. I then ran it using VPM-B on a conservatism of +3. Both dives were ascents straight to the surface. I would say it is an undeserved/unexplained hit. The OP could have been dehydrated, tired, or any number of things that contributed to it. As others have said, deco isn't an exact science.

 

[HIGHwing]

If you go by the computer, it was undeserved. If you go by the tables, witch of course do not give you credit for the shallower parts of the dive and require you to round up your depth, it would be considered deserved.

The profile - Dive 1-55.5 ft. 42:49. Surface interval 43:55 Dive 2-55.5 ft. 44:21. Ascent rate was less than 30ft./min. on both dives, much slower on first dive.

Sorry you got hurt, and glad to hear you're doing better. I always find it interesting when someone says the computer said it would be okay, the tables not so much. That makes me think there was enough depth variation within the dive that the only practical way to calculate the dive is either basically square, or whether or not the computer said you owed a mandatory decompression obligation. Obviously some computers push the limits more than others, but I've reached the point in my diving career that there are interpretations/models I know work for me more than others. Regrettibly, by way of live human self-experiment.

Please post the profiles so we can take a look.

 

[flots am]

Any ideas on what that could be? I was comfortable with this profile myself until I looked more closely at the tables. If something else is going on, I would sure like to figure out what it is.

Your computer was happy, and vPlanner was happy with +2 conservatism, even when run with way-too-slow ascent rates.

The only guesses I have are:

• Your computer isn't tracking time or depth properly, or
• There was something going on inside you.
• You had some sort of sawtooth profile.

Sorry, not much help.

 

[miked]

As a fellow member of the "undeserved/unexpected/unexplained DCS2 club", I'm sorry that you took the hit, and glad that you are feeling better. Thanks for posting, as it gives info/food for thought for the rest of the SB community.
Be well, dive safely.

 

[RJP]

Part of my brain would think PFO. Do you ordinarlilly dive EANx? Maybe that has been giving you a wider margin of error in the past, and diving air brought you over the edge.

Sure, as been said above diving/deco is inexact, but that usually explains the marginally "undeserved" hit... when people are right at the edge. There's nothing remarkable about those dives.

 

[Nirvana]

Can you link the study? Haven't seen that one.

I believe the article John was referencing is this one I have attached.

 

[openmindOW]

I'm posting this so that we all may benefit from whatever there is to learn here, and because I know there are experts on this board that could provide some of the best information available anywhere. And of course I feel like a genius for having DAN insurance, on top of my regular policy.

Thank you for posting.

I'm glad that you are okay.

I'm thinking PFO or too-fast an ascent rate or something. I recommend that you talk to a doctor.

Computers don't bend; divers do.

 

[beaverdivers]

Part of my brain would think PFO. Do you ordinarlilly dive EANx? Maybe that has been giving you a wider margin of error in the past, and diving air brought you over the edge.

Members have posted that your "hit" was deserved. Using their illogic, thousands of divers would be bent everyday. Are they?

I believe that there were factors that contributed to your "hit". Those factors are the reason that you got bent. Age, dehydration & PFO may have been elements. Also, diving 21% O2. If you would have been diving 32% EAN, 36% EAN or 40% EAN, would you have received the "hit"?

 

[Ken Kurtis]

I was taught to use bottom time not total dive time. If I went to 90' for 25 minutes and then used 3 minutes to ascend and 3 minute for a stop and 1 minute to ascend to record it as 25 minutes.

I've always taught NOT to count safety stop time as total dive time (or Total Nitrogen Time - TNT - to use the NAUI term). There's logic for this, especially using chrpai's example:

1. 25 minutes is the limit at 90 feet on the NAUI tables.
2. Bottom time is defined as from when you first begin your descent until you begin a direct ascent to the surface.
3. Technically, ascending to a safety stop is not an ascent to the surface so the TNT will be descent time, time on the bottom and at other depths, and time ascending to your 10' safety stop.
4. Let's stipulate that arrive at 10' at exactly 25:00 of the dive so right on the ND limit for these tables.
5. Here's the philosophical question: Do you accept the notion that stopping at 10' for 3 minutes (or more) results in out-gassing that lowers your total nitrogen load? (I do, and will proceed on that assumption.)
6. If I go strictly by table rules, I should blow off the safety stop and begin my direct 20-second ascent to the surface so I don't exceed the 25-minute NDL.
7. But by doing that, I will actually (theoretically) arrive at the surface with more N2 than I would have had I done the 3-minute stop at 10'.
8. Doing a safety stop for 3-minute at 10' reduces my nitrogen load and should redsuce my risk of DCS.
(SIDENOTE: Andy Pilmanis' early-90's study of high-altitude Air Force pilots showed that a 3-minute safey stop at 10' eliminates 90% of the asymptomatic bubbles that don't necessarily bend you but may set you up for a hit on a second or subsequent dive since the models are based on the presumption that you are bubble-less. So the OP's hit could have resulted from asymptomatic bubbles created on the first dive that then became a problem on the second dive, even though the computer showed no issues.)
8. But by doing the 3-minute stop at 10', if you add safety stop time in to the total dive time, you now have a 28-minute dive, which requires (on the NAUI tables) 5 minutes of deco at 10'.
9. There's no logic in saying that doing something that lessens your nitrogen load increases your nitrogen load and therefore your deco obligation.
10. In other words, there's no logic in saying doing a 3-minute safety stop adds another 5-minute stop obligation so you'd be safer to go to the surface without stopping at all.
11. And that's why I've always taught to subtract the safety stop, or more specifically, add in the safety stop as total time but if it pushes you over a ND limit, just go to the ND limit because it otherwise makes no sense.

- Ken