Deep Stops Increases DCS

[Dr Simon Mitchell]

Hello David,

Thank you for the comprehensive post.


If you don't like me pointing out Simon's use of junk science, then I suggest you influence him to stop doing it. But trying to bully me out of the picture so Simon and friends can keep his sham presentation going, ain't going to work.

The problem, Ross, is that David agrees with my interpretation of what you refer to as "junk science". I'm just the one who is stupid enough / motivated enough by diver education to be bothered engaging with you on these forums. As David has pointed out, your involvement in writing software to implement VPM (coupled with your authoritative internet behaviour) will inevitably cause some people to assume you have training and expertise in the relevant physiology and pathophysiology (which you don't). Couple that with the fact that you habitually peddle misinformation about important work conducted by true experts and which carries important safety implications, and it creates a collection of circumstances which I find difficult to ignore.

We can, of course, argue about what is "junk science" all day, but if people want to conduct their own appraisal of how much "science" the respective participants in this discussion have validated before their peers, all they need do is type Doolette DJ, or Hemingway R, or Mitchell SJ, into the pubmed search engine (www.pubmed.com). I freely admit that this does not resolve the debate taking place here, but as a scientist who is being accused of "junk science" I do contend that this might provide some sense of who is most (or least) likely to be promoting "junk science" here on scubaboard.

BUT you allow / encourage / standby / approve as Simon and friends do use it out of context, or incorrectly, and to use it beyond its useful purpose. These are the ones trying to "... attempt to apply it as “an overall measure”... ". They go on to make eye candy junk science graphs to play trickery on people. It is these people who "...are completely misrepresenting the use of, and the utility of, the summed integral supersaturation as a measure of decompression stress...". Are you happy with that? Perhaps you could put some effort into quashing that aspect. "Because of this, your willful lack of action is unconscionable, and you should be ashamed of yourself". ......

This is complete and utter nonsense. The discussions of integral supersaturation by myself and others have only ever occurred in the same context in which the concept was first applied by David.

So why do we need a second derivative of the primary measure, this "integral of supersaturation" to account for "duration", when both these components are addressed already? What these guys are attempting is to double up on the time component (or replace it) by adding up individual time slices.

David has answered this already.

Simon argues that peaks don't count, but clearly this dive example indicates that supersaturation peaks are the most significant aspect. It also demonstrates that "integral of supersaturation" is not a useful formula to use here.

I can see that I'm simply going to have to include this in every post (because this is about the 4th time I have said it). Did you not see the bit where I said:

I am well aware that extremely high tissue supersaturations can produce bubbling and symptoms with almost no delay. I am also aware that very low levels of supersaturation may be sustained for very long periods without the development of problems. However, these facts do not constitute a valid argument against time being important at levels of supersaturation between these extremes.

Simon M

 

[boulderjohn]

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A ScubaBoard Staff Message...

Although I am speaking in a moderator voice here, I am not actually moderating. I am just going to explain something related to the moderation of this thread. There have been some reports that have triggered moderator discussion, and I want to write a short treatise on the topic.

Ethos is a legitimate part of the art of persuasive writing and speaking, going back to its origin in classic Greek rhetoric. It supports the argument by either establishing that the speaker has the expertise to make the argument worthy of belief or showing that the opposing speaker is not worthy of belief. There is nothing wrong with that.

Modes of persuasion - Wikipedia, the free encyclopedia
Dr. Williams : USC Upstate : English Program / Ethos-Pathos-Logos-The-3-Rhetorical-Appeals​

A good example occurs with some frequency in the ScubaBoard in the Diving Medicine forum. People will post questions related to dive medicine, and they will get excellent answers from some of the diving physicians we are blessed to have on staff and from other physicians who are not on staff. Unfortunately, they often get incorrect information from unqualified but well-intentioned participants who are repeating something they heard somewhere. How is the reader to know whom to believe? Well, most people will believe the physicians solely because they are physicians. That is a legitimate use of ethos in persuasion.

An ad hominem argument is a fallacious cousin to the legitimate use of ethos. It comes when the attack on the credibility of the user does not have a real value to the argument. For a clear example, let's say that someone was arguing about a certain practice in cave diving, and someone countered by pointing out that the writer had been arrested for selling marijuana in his youth. That would be a clear ad hominem argument, since that previous conviction has nothing to do with the issue or the writer's ability to present an authoritative position.

So there are examples when discussing information about the speaker is obviously important and acceptable. There are cases when it is absolutely not appropriate. Unfortunately, there are many cases that are not so clear and could be argued either way.

The issue of speaker credibility has been raised a number of times in this thread. At times it has been done in ways that are clearly appropriate to the topic. At times, it has been well into the gray area. We have deleted some that were still in the gray area but were sliding in the ad hominem direction. This is a very important discussion, and I hope we can all remember to keep things civil and legitimate.

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[Nasser]

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A ScubaBoard Staff Message...

Although I am speaking in a moderator voice here, I am not actually moderating. I am just going to explain something related to the moderation of this thread. There have been some reports that have triggered moderator discussion, and I want to write a short treatise on the topic.

Ethos is a legitimate part of the art of persuasive writing and speaking, going back to its origin in classic Greek rhetoric. It supports the argument by either establishing that the speaker has the expertise to make the argument worthy of belief or showing that the opposing speaker is not worthy of belief. There is nothing wrong with that.

Modes of persuasion - Wikipedia, the free encyclopedia
Dr. Williams : USC Upstate : English Program / Ethos-Pathos-Logos-The-3-Rhetorical-Appeals​

A good example occurs with some frequency in the ScubaBoard in the Diving Medicine forum. People will post questions related to dive medicine, and they will get excellent answers from some of the diving physicians we are blessed to have on staff and from other physicians who are not on staff. Unfortunately, they often get incorrect information from unqualified but well-intentioned participants who are repeating something they heard somewhere. How is the reader to know whom to believe? Well, most people will believe the physicians solely because they are physicians. That is a legitimate use of ethos in persuasion.

An ad hominem argument is a fallacious cousin to the legitimate use of ethos. It comes when the attack on the credibility of the user does not have a real value to the argument. For a clear example, let's say that someone was arguing about a certain practice in cave diving, and someone countered by pointing out that the writer had been arrested for selling marijuana in his youth. That would be a clear ad hominem argument, since that previous conviction has nothing to do with the issue or the writer's ability to present an authoritative position.

So there are examples when discussing information about the speaker is obviously important and acceptable. There are cases when it is absolutely not appropriate. Unfortunately, there are many cases that are not so clear and could be argued either way.

The issue of speaker credibility has been raised a number of times in this thread. At times it has been done in ways that are clearly appropriate to the topic. At times, it has been well into the gray area. We have deleted some that were still in the gray area but were sliding in the ad hominem direction. This is a very important discussion, and I hope we can all remember to keep things civil and legitimate.

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I'm sorry but I find this post too didactic and verbose and not particularly comprehensible. If we find ourselves in the fortunate position of having members of this forum from all over the world - some of whom do not speak english as a first language, then I think it would be to everyone's benefit to condense and summarize the above in a more accessible way.

Thank you.

 

[boulderjohn]

I'm sorry but I find this post too didactic and verbose and not particularly comprehensible. If we find ourselves in the fortunate position of having members of this forum from all over the world - some of whom do not speak english as a first language, then I think it would be to everyone's benefit to condense and summarize the above in a more accessible way.

Thank you.

Sorry, I did not mean to speak over people's heads. Here is the Reader's Digest summary.

1. Some people reported posts for being attacks on individuals, using the term ad hominem in the description.

2. In argument, the capability of the arguer can sometimes be important. If a highly capable person is making an argument in his or her area of expertise, that person's expertise is a good point in support. If the person has no expertise in that area, then that is also a good point in opposition.

3. Attacking a person for reasons that do not have anything to do with the argument are not good and are not allowed here.

4. Please be careful.

 

[rossh]

A couple of good questions at this point might be:

What is integral supersaturation (ISS)?

Integral supersaturation is a pretty simple concept. Decompression sickness occurs due to the release of dissolved gases after a dive. How many bubbles will form and how big they get is a function of 1) the speed of the release (that's the pressure of the gases being released), and 2) the time those pressures are allowed to exist. Higher pressures can be endured for a short time and lower pressures for a longer time. The thing to remember is that the TIME you're exposed to supersaturation is important.
Kevin Watts

This concept is well understood and used everyday. The simplest example is an NDL dive vs decompression dive at the same depth. The existing models and methods fully address this.

ISS is a measure of the speed and time of decompression.
Kevin Watts

The existing Haldane and Schriener equations in models, already provide exactly that information to the deco model.

Simply looking at charts of peak supersaturation gives you an idea of speed, but is not a good measure of the overall supersaturation-time you're exposed to.
Kevin Watts

Wrong. The maximum sustained value of supersaturation is all the information that is required. That information is provided already by Haldane and Schriener equations in today's models. The time or "duration" is provide through the half times of the cells your using to measure supersaturation with. The rate of increase / decline of supersaturation pressure is a dependent on cell half time.

Integral supersaturation measures both pressure and exposure time and so can be thought of as an index of decompression stress (supersaturation pressures you're exposed to and the time you're exposed to them) when comparing dives with a similar run time. Pretty simple idea. Its not the rosetta stone of decompression, but it is an interesting and useful measure as Dr. Doolette has described.
Kevin Watts

....but only *IF* it's used properly... Evidently from below, we see your method is flawed, and the charts do not present any useful information.

Why does Ross seem desperate to discredit ISS?
Kevin Watts

Because Ross doesn't like junk science. He doesn't want to see the dive theory and its understanding to be riddled with garbage explanations. Ross puts high value on the truth.

Here is your diagram, with some truth added:

 

[igor p]

I am well aware that extremely high tissue supersaturations can produce bubbling and symptoms with almost no delay. I am also aware that very low levels of supersaturation may be sustained for very long periods without the development of problems. However, these facts do not constitute a valid argument against time being important at levels of supersaturation between these extremes.

Simon M

Hi Simon,

I belive you forgot to mention in your citation that tissue can sustain quite high supersaturation for long periods if there is no provoking stress arround. Or better described:
- if the change in pressure is slow and not significant tissue can sustain higher supersaturation for longer periods,
- if change in pressure is fast and significant tissue can not sustain higher supersaturation for longer periods or can sustain high supersaturation only for very very short periods.

The most important point in decompression beside doing stops is the travel time/speed between stops.

 

[PfcAJ]

I'm sorry but I find this post too didactic and verbose and not particularly comprehensible. If we find ourselves in the fortunate position of having members of this forum from all over the world - some of whom do not speak english as a first language, then I think it would be to everyone's benefit to condense and summarize the above in a more accessible way.

Thank you.

im a native speaker and I think it's too verbose too. You're not alone.

 

[UWSojourner]

… blah blah …

Whatever.

...

A useful post is here.

 

[Dauntless]

The more time you spend in the pigpen, the more mud you get on you, seems logical to me.

 

[Michael Guerrero]

OMG...it's like we're in the twilight zone. I think the entire cast of characters is here now.