Understanding M-Values by Erik C
Understanding M-values By Erik C. Baker, P.E. In conjunction with an array of hypothetical tissue compartments, gas loading calculations and M-values
docslib.org
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As there have been no additional comments regarding this publication, I will share a few thoughts I had after reading it that I jotted down in the margins of the paper.@boulderjohn @dmaziuk
DAN Europe article from 2017, a interesting read. PDF can be downloaded from the link
Frontiers | Dive Risk Factors, Gas Bubble Formation, and Decompression Illness in Recreational SCUBA Diving: Analysis of DAN Europe DSL Data Base
Introduction: The popularity of SCUBA diving is steadily increasing together with the number of dives and correlated diseases per year. The rules that govern...www.frontiersin.org
The study includes 2,629 divers and 39, 099 dives. They had 320 cases of DCS, for a rate of 0.82% or 82 cases/10,000 dives. This is significantly higher than the rate of somewhere around 1-3 cases/10,000 dives in recreational dives usually cited. There is no discussion of this rate.
This is a great article.Understanding M-Values by Erik C
Understanding M-values By Erik C. Baker, P.E. In conjunction with an array of hypothetical tissue compartments, gas loading calculations and M-valuesdocslib.org
Thanks, I did not get it that way, I would not have expected that. I'll have to go back and read it over again. Seems like that would have been very obviously stated in the methods, maybe it was.I remember now: it seemed to be the case having two unrelated studies that, while informative, would not merit individual publications. So they mashed them together into one confusing article: the analysis of 40K NDL dives appears to be completely unrelated to the analysis of the 320 DCS cases; as I recall there was no indication that there's any intersection in the 2 datasets in the paper.
So this is wrong:
They had 320 cases of DCS in the database of 320 DCS incidents (i.e. 100%), and zero reported cases of DCS (i.e. 0%) in the 40K dives, is my reading of their paper.
My reading as well. Moreover, 39k of the 40k dives weren't used for anything other than a description of the dives. They did Doppler studies on 970 of the dives and the largest section of the paper was looking at bubble grades versus various factors related to those dives and divers.I remember now: it seemed to be the case having two unrelated studies that, while informative, would not merit individual publications. So they mashed them together into one confusing article: the analysis of 40K NDL dives appears to be completely unrelated to the analysis of the 320 DCS cases; as I recall there was no indication that there's any intersection in the 2 datasets in the paper.
They had 320 cases of DCS in the database of 320 DCS incidents (i.e. 100%), and zero reported cases of DCS (i.e. 0%) in the 40K dives, is my reading of their paper.
Hi @FishWatcher747...The Saul statistics listed above appear not to make a distinction between Type 1 and Type 2.
As there have been no additional comments regarding this publication, I will share a few thoughts I had after reading it that I jotted down in the margins of the paper.
The study includes 2,629 divers and 39, 099 dives. They had 320 cases of DCS, for a rate of 0.82% or 82 cases/10,000 dives. This is significantly higher than the rate of somewhere around 1-3 cases/10,000 dives in recreational dives usually cited. There is no discussion of this rate. (see comments in posts 33, 35 and 36)
Nearly 74% (236/320) of the cases of DCS occurred in divers with a GF of 0.7-0.9. Unfortunately, there are no denominators for the GFs. I would not be surprised if these GFs were also the most common in all of the dives.
As per @dmaziuk it was not surprising that most cases of DCS implicated the medium compartments.
There is interesting information here, as often, to be taken with a grain of salt.
I remember now: it seemed to be the case having two unrelated studies that, while informative, would not merit individual publications. So they mashed them together into one confusing article: the analysis of 40K NDL dives appears to be completely unrelated to the analysis of the 320 DCS cases; as I recall there was no indication that there's any intersection in the 2 datasets in the paper.
So this is wrong:
They had 320 cases of DCS in the database of 320 DCS incidents (i.e. 100%), and zero reported cases of DCS (i.e. 0%) in the 40K dives, is my reading of their paper.
@dmaziuk and @lowwall are correct. This was 2 separate analyses reported in one publication.My reading as well. Moreover, 39k of the 40k dives weren't used for anything other than a description of the dives. They did Doppler studies on 970 of the dives and the largest section of the paper was looking at bubble grades versus various factors related to those dives and divers.
And then there was a section summarizing the completely separate set of dives that made up their DCS database.
All in all, it looks like they'd hoped to get some DCS cases as part of the big study, but when they didn't, they scrambled to come up with something they could get published somewhere. I'm going to assume it's no coincidence that it appeared in Frontiers in Psychology, a pay to play journal in an unrelated field, instead of one of the normal landing spots for decompression research.
To me the most interesting part of this was the lack of DCS cases amongst the 40k dives. I will hypothesize that this is attributable in large part to self-selection and observer effects. Basically, that people volunteering for such a study and aware that they are going to be reporting all aspects of a dive are going to be much more careful and conservative in that dive than the average diver.
@scubadada it's interesting you say the M-value line shifts right going to ZHL-C. I picture it shifting down.The slope of the M-value lines was not changed, so this resulted in shifting the M-value line to the right, more conservative.
The intercept, Mo, shifts down, as the slope does not change, the line shifts right. I'll share that beer with you.@scubadada it's interesting you say the M-value line shifts right going to ZHL-C. I picture it shifting down.