Question Any information on increased nitrogen uptake by a panicking diver?

[JonG1]

Shear forces in muscle in vigorous exercise are correlated with bubble formation, so that makes sense.
And injury kinins may play a role.
Lots still to learn...

I very nearly bent my shoulder after a decompression dive, after I wrestled the loop bungee off my sm bailout at the 6m stop.

The angle of my shoulder and force applied translated to very low level pain and throbbing as I dekitted. Didn't develop but I've had tissue bends before and the sensation is quite distinct.

Coincidentally I think you were on the boat Wibble.

 

[rsingler]

Having just read the paper in question, it's not obvious to me that we have clean data. I don't see that the GF was downloaded from a computer, but rather that it was calculated somehow from a) analysis of some computer download, or b) computed from reported dive characteristics. I just don't know. It says that 39,000 dives were digitally recorded, so I presume there's some sort of computer download.
But let's assume that the GF data is valid. Here's what they say:

To which my response is, "Wait! What!?"
A "deserved" hit is one whose GF is over 1 and all the others are undeserved ??? Not in my world.

If I look over the dives I do (including deco), the vast majority end with a surfacing GF<50, which I presume is the same as their GF 0.5. And every deco dive ends with a GF <70. If I'm wrong about their terminology, somebody correct me.
But if that's true, their whole database of DCS cases is skewed toward higher surfacing GF's than my dives, and all this population reflects is the distribution of GF's among bent divers. "Only 8%" has GF's over 1 because damned few dives end that way. If it's 8% of your sample DCS population when it's 1% of dives, I'd say that's a pretty definitive association. But we don't have a denominator.
And the plurality of DCS cases occurring in the GF70-90 range tells me that they're the majority of dives that are pushing my envelope. To me, the "undeserved" hits (which are probably just missing some key additional data) are the DCS cases occurring at GF<70 (14.6%). Those are the ones I'd want to look at.

I am not overly impressed with this study, though the conclusions make some sense.

Am I not understanding how they are measuring GF?

 

[Angelo Farina]

Just wondering if there is any information or thoughts on whether a panicking/scared diver at depth will take on more nitrogen than normal? By panicking I am thinking of things like a diver that suddenly has a close encounter with a dangerous species of shark, has a really bad leg cramp that they can't deal with alone and are are in considerable pain etc - things that result in a more rapid breathing rate and higher heart rate. Any thoughts would be appreciated.

The Bulhmann algorithm explicitely takes into account the effort. Air consumption in considered a good proxy for effort.
Also heart rate and water temperature can be monitored and taken into account.
Some Scubapro-Uwatec computers equipped with air pressure monitoring (and optionally heart rate monitoring) take these factors into accout and increase the duration of deco stops accordingly, as explained here:

https://scubapro.johnsonoutdoors.com/eu/en-gb/shop/computers

 

[dmaziuk]

Dive Risk Factors, Gas Bubble Formation, and Decompression Illness in Recreational SCUBA Diving: Analysis of DAN Europe DSL Data Base

 

[dmaziuk]

Having just read the paper in question, it's not obvious to me that we have clean data.

We've been through this at least twice already. There is no indication that the 40K dives in part I are in any way, shape, or form, related to the 320 DCS cases from part II.

As a curious side note, the database of 320 DCS cases contains 8 + 14 + 120 + 116 + 46 + 10 + 3 = 317 cases where GF was present. Presumably the other 3 were single and/or had BFs rather than GFs at the time. I.e. not having a GF reduces one's risk of DCS to 3/320 -- that's the posterior probability, taking into account the 100% DCS rate in the sample.

Edit: or perhaps happily married without a GF on the side.

 

[scubadada]

Is there data on how close to NDL undeserved hits occur?

https://docslib.org/doc/3857326/understanding-m-values-by-erik-c

scubaboard.com

 

[inquis]

The Bulhmann algorithm explicitely takes into account the effort. Air consumption in considered a good proxy for effort.

Personally, I would reserve the term "Buhlmann algorithm" for the Buhlmann ZHL16-<variant> employed by Shearwater, Garmin, Mares, Deep6, et. al. ScubaPro does have their "ZHL8 ADT MB" algorithm that may have originated from one of Buhlmann's works, but they've put their own proprietary spin on it to try to incorporate breathing rate, heart rate, temperature. Buhlmann is not mentioned in ScubaPro's literature; e.g., the Galileo Luna.

 

[rsingler]

Is there data on how close to NDL undeserved hits occur?

https://docslib.org/doc/3857326/understanding-m-values-by-erik-c

scubaboard.com

Oops! I thought I'd seen this discussion before.
Sorry, folks.

 

[L13]

I am not overly impressed with this study, though the conclusions make some sense.

Am I not understanding how they are measuring GF?

Like you I don't consider a GF <1 to be the definition of an undeserved hit. The data does make me feel good about trying to always surface with GF < .7 (preferably GF < .5) unless there is a real need for urgency.

The % column appears to be % of DCS, not % of dives. I think you understand their GF correctly.

 

[Umpman]

Just wondering if there is any information or thoughts on whether a panicking/scared diver at depth will take on more nitrogen than normal? By panicking I am thinking of things like a diver that suddenly has a close encounter with a dangerous species of shark, has a really bad leg cramp that they can't deal with alone and are are in considerable pain etc - things that result in a more rapid breathing rate and higher heart rate. Any thoughts would be appreciated.

A panicked diver could possibly have a higher amount of CO2 because of the panicked breathing.