Bent. I guess it really can happen to me.

[Ken Kurtis]

Average depth of first dive was 45.5 ft. Second dive - 47.1 ft. Both were fairly square, 50 ft. dives.

Emphasis added . . .

In addition to the possibility of first-dive asymptomatic bubbles, a square profile could also factor in. Computers tend to do better (so the mfgs say) on multi-level profiles rather than square. If you know you'll be diving a square profile, you might be better off using tables. Altough Jim's tables may present an extreme example of the deco obligation, even the NAUI tables would be giving you 60/50, H, 44 min SIT makes you G, G to 60 has 44 RNT, add in 44 more for bottom time gives you 60/88 which reads off the NAUI tables. The highest they go is 60/80, resulting in a 7-minute deco obligation at 15'. But the same (rhetorical) questions remains: If you had known all of this ahead of time, would you still have done the profile, regardless of what the computer was saying you could do?

 

[boulderjohn]

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

The study was done in 2004. Check out the bubble score on the final graph.

---------- Post added September 4th, 2013 at 01:30 PM ----------

If that's the study I think it was the methodology was dumb. A 10 ft/minute ascent rate from the bottom is less an ascent rate and more an extension of your bottom time. Need to get up to the depth at which offgassing starts reasonably quickly. A 1 foot/minute slow ascent from a 300 foot dive is not going to help much!

That's the point--an ascent rate that is slower than optimal is ongassing too much.

 

[Tigerman]

A SAC of .4 seems pretty good - typo?

Do you have any references supporting your suggestion that breathing technique has an effect on on-gassing and off-gassing of N2 to the extent that it may lead to DCI?

My SAC is .45-.55 on a normal dive. .4 for a woman Id say is not very low..

Sent from my GT-I9300 using Tapatalk 4

 

[HIGHwing]

I'm making a pretty decent trimix dive this weekend, and I don't want to piss on Karma and end up bent. Accordingly, I'm going to be quiet.

 

[beaverdivers]

I'm making a pretty decent trimix dive this weekend, and I don't want to piss on Karma and end up bent. Accordingly, I'm going to be quiet.

I'll be teaching in the pool this weekend. My students & I will be using AI dive computers. I believe my risk of DCS is quite low.

Let the discussion continue...

 

[lowviz]

The study was done in 2004. Check out the bubble score on the final graph. ...//...

Yes, I did. I also have a serious concern with the statistical tests vs. the confounding effects of PFO's.

I didn't see any effort to tease out "susceptible" divers. Not like there is a low incidence of PFO's in the general population: Incidence and Size of Patent Foramen Ovale During the First 10 Decades of Life: An Autopsy Study of 965 Normal Hearts

 

[beaverdivers]

Thanks again to the OP for posting this story.

The Question is " What factors led to the OP's bends? "

Yes, he had done this day of diving hundreds of times. Yes, he felt that he had proceeded as he had many times before.

But obviously, many factors caused the OP to get bent. This case does not seem to be a simple one of Too Deep - Too Long.
I'm sure there are many real subtle factors that contributed to his "hit".

This "hit" was undeserved. However, if I were the OP, I would want to figure out how to avoid a future "hit".

Good Luck & Good Diving!

 

[tracydr]

Were you warm at the beginning of the dive? Did you ever get chilled? What were the temps and your exposure protection?

 

[Ken Kurtis]

But obviously, many factors caused the OP to get bent.

You don't know that. It's a statement that can't be supported. It could have been one thing. It could have been an esoteric combination of things.

In fact, given that his symptoms fully resolved on O2 and didn't come back, how do we even know he was really bent? Just because he emerges from the chamber fully resolved doesn't necessarily mean he was bent in the first place. If you were fully resolved when you went in, the chamber ride won't change that. And once someone's resolved, how do you prove they were bent yobegin with???

IMHO, there's nothing "obvious" about this incident and blanket all-purpose statements like that don't really help people learn. There's a lot of stuff about nitrogen and the bends that remain a mystery. And sometimes the answer is "We don't know."

- Ken

 

[pocky21]

Techdeep - as a member of the chamber riders club, I feel your pain. I would be very upset if I did not have a known reason for my DCS hit.

After reading this thread, I'm curious about how each of us approach our own relative risks of DCS and what we do to mitigate said risk - to avoid a derailment, I started a new thread on the subject here: http://www.scubaboard.com/forums/ad...ng-dci-risk-factors-adjusting-dive-plans.html

Glad to hear it all worked out well for you, TD. Those hospital bills are ridiculous, aren't they! Hope the food was at least palatable