horizontal ascents

[SparticleBrane]

40 posts/page is very nice, much less clicking to get to another page.

 

[lamont]

That's not how the "business" of scientific or medical research works. But I get the impression you see it's an anti-DIR plot. I hate to burst your bubble but if the folks who actually know about these things suspected that even a small percentage advantage could be gain they'd be on it in a flash, and most of them have never heard of DIR.By definition, theory and anecdotes (I don't know why you say anecdotes in this case, it's more like claims ... which are quite different) will not do, and youknow that.It's kind of silly to point out to people that a claim concerning how to best perform decompression has no basis in fact? Hardly. Its worse than "kind of silly" to spread untested and unverified BS concerning decompression and not label it as "pure conjecture, not to be confused with even a creditable opinion."

We do know that poorly perfused tissue can take hits. Not wearing gloves on cold water dives has been linked to getting hits in the hands and arms. I believe there's also medical studies on cold water decompression which back this up.

This has led a lot of technical divers to focus on trying to reduce all kinds of stress to tissues on decompression. Not only do you want to make sure that your body is warm on deco, but you don't want to be hanging off an upline that is boucing around due to wave action or causing wrist strain due to fast currents (hence the use of scooters or jon lines).

Better bloodflow and perfusion can be expected in the horizontal position vs. the vertical position because the heart has to do less work to pump blood because it doesn't have to overcome a pressure gradient. It is indeed open to debate as to if this makes a real scientifically measurable difference on decompression and i don't know of anyone getting an ankle-bend due to vertical decompression, but you're going way overboard calling it "not to be confused with even a credible opinion". It is just an extrapolation from known stressors that are known to increase risk of DCS to a stressor which has an unknown and not measured effect on decompression. Given the other reasons that a predominantly horizontal posture is good for mobility on decompression, I would list the theory that it also assists decompression as a positive.

And I do know someone who took an arm hit which was thought to be because of his use of wetgloves with the fingers cut off and poor perfusion. From that I extrapolate both that deco which causes wrist strain due to hanging off an upline is also probably bad, and that horizontal decompression is probably somewhat better than vertical decompression. Just because nobody has or can measure the effects doesn't mean that I'm not going to make some educated guesses about what is going on during decompression and how to minimize risk -- particularly when diving in cold 45F water where tissue perfusion issues become larger. No I don't have scientific evidence to directly back up horizontal ascents being better for decompression, and no I don't use this *primarily* as a reason to prefer being horizontal on deco, but I do include it as a factor in the positive column because it seems plausible and in-line with other practices which have better validation.

 

[MXGratefulDiver]

ummmmm theres only 4 pages so far

OK, let me put it a different way ... notice both the tone and content of the posts from 2002 to 2004 ... then the ones that have been posted in the past few days.

See anything different?

... Bob (Grateful Diver)

 

[lamont]

ummmmm theres only 4 pages so far

i'm on page 7

the 10-post-pagers just haven't seen the light yet...

 

[Rainer]

Um, page 4...

 

[ekewaka]

Wow..... dual hosed argon.. hadn't thought of that.

Could it be for his backup drysuit?

 

[Thalassamania]

We do know that poorly perfused tissue can take hits. Not wearing gloves on cold water dives has been linked to getting hits in the hands and arms. I believe there's also medical studies on cold water decompression which back this up.

My understanding is that comes under the heading of anecdotal findings with a theoretical explanation. Perhaps there are studies that directly relate, I'll have to check.

This has led a lot of technical divers to focus on trying to reduce all kinds of stress to tissues on decompression. Not only do you want to make sure that your body is warm on deco, but you don't want to be hanging off an upline that is boucing around due to wave action or causing wrist strain due to fast currents (hence the use of scooters or jon lines).

You don't hear me objecting to a Jon line or to gently swimming into a slight current to keep warm.

Better bloodflow and perfusion can be expected in the horizontal position vs. the vertical position because the heart has to do less work to pump blood because it doesn't have to overcome a pressure gradient. It is indeed open to debate as to if this makes a real scientifically measurable difference on decompression and i don't know of anyone getting an ankle-bend due to vertical decompression, but you're going way overboard calling it "not to be confused with even a credible opinion". It is just an extrapolation from known stressors that are known to increase risk of DCS to a stressor which has an unknown and not measured effect on decompression. Given the other reasons that a predominantly horizontal posture is good for mobility on decompression, I would list the theory that it also assists decompression as a positive.

We're talking what, 150 mm of mercury head to toe? Maybe 70mm from lung to to bottom (where the gas exchange is)? This is an extrapolation of a theoretical construct lacking either anecdotal or experimental evidence. "Not to be confused with even a credible opinion," is hardly going way overboard in this case. Pose it as a hypothesis for testing perhaps, but nothing more at this point.

And I do know someone who took an arm hit which was thought to be because of his use of wetgloves with the fingers cut off and poor perfusion. From that I extrapolate both that deco which causes wrist strain due to hanging off an upline is also probably bad, and that horizontal decompression is probably somewhat better than vertical decompression.

And … with all due respect, if my grandmother had two wheels she'd be a bicycle.

Just because nobody has or can measure the effects doesn't mean that I'm not going to make some educated guesses about what is going on during decompression and how to minimize risk -- particularly when diving in cold 45F water where tissue perfusion issues become larger. No I don't have scientific evidence to directly back up horizontal ascents being better for decompression, and no I don't use this *primarily* as a reason to prefer being horizontal on deco, but I do include it as a factor in the positive column because it seems plausible and in-line with other practices which have better validation.

I see no plausibility transferred to the idea that horizontal position promotes better decompression by anything that has been discussed here.

Is it going to do you any damage? Of course not.

Is there any reason not to do it? No.

Is it likely to be of any use? No.

I don't use this *primarily* as a reason to prefer being horizontal on deco.

The DIR reason for horizontal positioning during deco is this:

Besides all the cool stuff, looking around for objects (?) and the like, consider this.
If you're not horizontal, you're not decompressing. .

Those are possible side benefits of a horizontal ascent but the main reason is that the body decos out better when horizontal.

You deal with this foolishness, please.

 

[lamont]

You deal with this foolishness, please.

I'm not going to disagree that as a *sole* answer to the question of "why do deco horizontal?" the "because you decompress better" argument is very weak. And it is a little painful to read statements like it alone settles the matter that decompression should be done horizontally.

I'd also agree that its barely hypothesis and more of a conjecture. But at this point decompression is still about 9/10ths voodoo anyway. So, given that there's little downside to decompression horizontally, and there's advantages to your mobility in doing deco horizontally, I find the conjecture that it may have small positive effect on decompression to be worth counting in the plus column.

And I seriously doubt that the converse is true and that vertical decompression could ever be shown to be more effective. The worst is likely to be that there's no effective difference. In which case I'm still not about to switch to vertical decompression...

YMMV.

 

[Thalassamania]

I'm not going to disagree that as a *sole* answer to the question of "why do deco horizontal?" the "because you decompress better" argument is very weak. And it is a little painful to read statements like it alone settles the matter that decompression should be done horizontally.

I'd also agree that its barely hypothesis and more of a conjecture. But at this point decompression is still about 9/10ths voodoo anyway. So, given that there's little downside to decompression horizontally, and there's advantages to your mobility in doing deco horizontally, I find the conjecture that it may have small positive effect on decompression to be worth counting in the plus column.

And I seriously doubt that the converse is true and that vertical decompression could ever be shown to be more effective. The worst is likely to be that there's no effective difference. In which case I'm still not about to switch to vertical decompression...

YMMV.

Now that's a rational outlook.

 

[diveasr]

im sorry i try to always show as many posts per page as possible

youre right it has changed