Deep Stops Increases DCS

[victorzamora]

and another one:
German teen solves 300-year-old mathematical riddle posed by Sir Isaac Newton | Fox News

Actually, you used a fantastic example against yourself. Newton never posed "the problem", he simply never worried about the solution. If I remember it right, Newton's mention of it was as an example of something that could easily be solved by classical methods...and the solution was a classic differential equation.

I looked up the equation he derived and I can confirm, it's nothing beyond an Undergraduate mathematician. A source I found quotes it as "Second- or Third-year University level" and "exceptional and remarkable for a high-school student, but standard for professional mathematicians."

Even if he did solve something Newton said was impossible, Storker responded correctly. Kid used science and math to solve a problem he found interesting.

 

[KevinNM]

Nope. This isn't an example of how "common sense" prevails over science. It's an example of a young genius solving a problem which scientists had struggled with. That some of those scientists had stated that the problem was unsolvable isn't the same as science being wrong.

"When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong."

 

[Storker]

"When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong."

Clarke's first law

 

[Shotmaster]

Some people outsmart themselves. Ego can ruin you. I have found it is better to let others sing your praises than to blow your own horn. All the greats that I have been fortuneant to know, all had a certain humbleness about them. I like to think of it as having class. When you start disrespecting an adversary that is a reflection upon you.

 

[leadduck]

Aye, and what % of the population have a PFO again? ;-)

Consider also that PFO is not the only way how bubbles can bypass the lung.
Seems like almost everybody has shunts inside the lung that widen during exercise, see: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1665323/
So I guess although only a minority of divers (25%?) has PFO, many more will see VGE arterialization.

 

[huwporter]

Wait....let me get this straight.

Gradient Factors: Mathematical addition of conservatism to a model based on percentage of acceptable tissue tensions....but it's complete bunk because it's "made up."

VPM-B/E: Some changes some guy made at random were implemented because it worked that one time.

Spot on. And you can add; Gradient Factors: Mathematical addition of predictable conservatism to a model based on percentage of acceptable tissue tensions that was tested by real man dives....but it's complete bunk because it's "made up."

VPM: Start with a hypothesis and then tweak the constants used so it lines up in a few instances with the other model above which was man tested, but do zero man testing of the instances where it is wildly different... and this makes it a "proper model".

 

[leadduck]

Compare that to known VGE. We know 25% have a PFO, and are potential arterialized VGE (artVGE) candidates. We know that up to half of us will make artVGE from post dive exercise. We know that most of can make some artVGE after a dive,
That's a huge gap between the conditions of artVGE, and the injury from the same ... 25 to 50% vs 0.02%. That needs to be explained, and trying to make every one do double deco today, is not the answer.

At first "some artVGE" is not sufficient, you need "plenty of artVGE" for a hard hit. The bubble grade plays a role. Many dives just cause a little VGE with very low probability of severe DCS requiring treatment, but nevertheless subclinical symptoms and fatigue.

In this paper
https://www.uhms.org/images/DCS-and-AGE-Journal-Watch/eftedal_umo_vge_and_decompre.pdf
they also consider transient pains and itchings together with severe DCS, calling them altogether "adverse effects of decompression", and conclude again that
a) all cases with low bubble grades show no adverse effects of decompression
b) the probability of adverse effects grows with the bubble grade
c) the high sensitivity of VGE with respect to adverse effects of decompression makes bubble detection a valuable tool for evaluation of the safety of sub saturation decompression tables

One interesting thing here is "sub-saturation". The authors mention a study on saturation diving, with a higher proportion of DCS cases not accompanied by detectable bubbles, particularly musculosceletal DCS in the lower limbs.
Could be that looking only at bubbles growing in tissues is sufficient for saturation diving, but not for technical/recreational.

 

[emmbee]

Consider also that PFO is not the only way how bubbles can bypass the lung.
Seems like almost everybody has shunts inside the lung that widen during exercise, see: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1665323/
So I guess although only a minority of divers (25%?) has PFO, many more will see VGE arterialization.

Thanks. You could have added that this is nothing new: check out the references. It's nothing new in the diving world, either. If you got a copy of Tauchmedizin, look at the circulation diagram in section 5.1, the A-V shunt is right there (in 5th ed, 2002, it's on page 95).

That's not the real problem, tho, IMHO.

Let me try to put Ross's argument in a different context, to try to make it clearer: speeding.

The rate of road accident is low, 0.05%. Accidents due to speeding is "far less of a problem still", 0.02%.

Compare that to known speeding. We know 25% drive above the speed limit often. Half of us sometimes.

That's a huge gap between speeding and the accident rate, and trying to reduce speeding is not the answer.

This is not a problem for 99.97% of us, at all.

There's (at least) two problems with this:

1) It ignores the magnitude of the excess. You can't just reduce it to a binary situation, VGE/no VGE vs DCS/no DCS or speeding/no speeding vs accident/no accident. Speeding by 5 (km/h, mph, whatever) is not the same as speeding by 50. Likewise a small VGE grade is not the same as a high VGE grade. If there is a correlation between magnitude and rate of accident, that's a rather strong indication that the two are linked, or rather, in this case, that one causes the other. Such a correlation exists for VGE grades and DCS.

2) It ignores the context of the excess. Speeding on a highway is not at all the same as speeding on a small winding 1.5 lane wide country road with a hedge on both sides. Likewise a high VGE count on a no-deco dive with bubbles originating from the very fastest tissues lodging themselves in slightly less faster ones that won't be controlling because they already allow ascending to the surface is not really a problem. On the other hand bubbles from slow-ish tissues lodging themselves in highly loaded next controlling compartment slower ones, that's a problem.

Cheers,

Matthieu

 

[emmbee]

but in truth we have seen lot of times simple man solve the most complicated enigmas where scientists didnt have a clue.

Is that right? Cool! Why don't you begin by addressing the problem I had with Bruce Wienke's published paper, then?

That one.

Cheers,

Matthieu

 

[igor p]

Is that right? Cool! Why don't you begin by addressing the problem I had with Bruce Wienke's published paper, then?

That one.

Cheers,

Matthieu

Sorry Mathiew,

if YOU think paper is wrong, YOU need to do formal review and reject the paper.