horizontal ascents

[pickens_46929]

Tennis court anyone?

http://www.lib.mcg.edu/edu/eshuphysio/program/section4/4ch3/s4ch3_29.htm

 

[pickens_46929]

Horizontal vs. Upright question...

http://www.lib.mcg.edu/edu/eshuphysio/program/section4/4ch3/s4ch3_34.htm

 

[cdennyb]

Here's some stuff for all you doubters out there to mull over.
Don't hate the player, hate the game.

reprinted with permission from George I.
Article from WKPP archive 1998
Minimum Decompression
By George Irvine
The fastest on gassing occurs in the early stages of any dive, the slowest on gassing as time passes. Whenever you dive, you are loading up rapidly in the first few minutes. This gas needs to be eliminated in the proper fashion, not ignored. Sometimes, the proper fashion is merely a 30 FPM ascent rate, as in diving to 300 feet in a total run of 5 minutes and then back up in 10 minutes. As the dive gets longer, the deco at first jumps and then starts to slow its increase and eventually levels off at saturation.
For dives in the 5-18 minute range, screwing up the deco is not necessarily a life-threatening event, and anything will pretty much get you off the hook. However, it is best to treat these dives as "minimum" deco requirement dives and use no shorting of the schedule. Beyond 20-30 minutes you are in the "mandatory deco" range, where you must not blow off the deco or you will likely be severely injured from it. If you really screw up on a dive like this, but are able to get at least 20 minutes on oxygen at 20 feet, your survival rate will be acceptable.
The mandatory range merely requires "correct deco", not excessive of prolonged deco, just the correct shape and approximate time. It is here and beyond that you can start using the techniques outlined in my previous post. Maximum deco is outlined in an example of a dive that I did with JJ this year. It does no good, and actually more harm to go beyond maximum deco, both in terms of oxygen damage and in terms of how the tissues relatively load and unload. Spending too much time at intermediate steps will merely load up the wrong tissues and make the upper steps less successful.
Keep in mind in minimum deco that the body's reaction to pressure changes is not necessarily instantaneous. This is why commercial divers can get out of the water from 40 feet, change out of their suit, and get into a chamber if they do so within five minutes. I do not know if this is still practiced in, but this alone should give you some clue as to why "minimum” deco is a must. Passing through the depth ranges on the way up too fast does not give the body's tissues time to off gas into the blood stream. It takes at least two minutes for the blood to make a full pass through the body, and it takes a while for the gas to make it out. If you trap it, which is what happens when minimum deco is ignored, it will merely cause symptoms later when you are on the surface, sub clinical symptoms, like tiredness, flu like symptoms, etc.
I am the fastest decompresser there is, but I do not do anything that is not the right shape or anything that is inadequate. When you look closely at what I do, you will find that for most dives, my deco will be more involved than what is prescribed by any program, will be longer for short dives, and shorter for long dives, will be shorter for helium, and infinite for nitrogen based gasses.

===================================


Did anyone have information to contradict the hundreds and hundreds of dives the WKPP did without incident? or... did someone have information to contradict the laws of physics concerning the pressure differential of the water column (fresh or salt) ?

thank you.

db

 

[Thalassamania]

questions and links

Ah ... like a big dose of Thorazine.

 

[cdennyb]

those articles are very nice, for the surface ambient pressure. But how do those equations enter into the pressure differential encountered when returning from a deco manadatory dive?

 

[JeffG]

Here's some stuff for all you doubters out there to mull over.
Don't hate the player, hate the game.

<snip>

thank you.

db

When in doubt (or when you have no real knowledge)

Quote someone else.


LOL


So tell me...where in that text is the word horizontal?

 

[Soggy]

Soggy looks to see where George talked about being horizontal.

He didn't.

In fact, much of WKPP deco is done in troths with their heads out of the water where they are vertical.

No one is arguing that being horizontal isn't more efficient than vertical from a decompression efficiency standpoint. However, the practical effect of a few feet of pressure differential is likely pretty minor. There are a lot of good reasons to be horizontal. That is one of them.

 

[cdennyb]

Multitissue models, variations of the original Haldane model, assume that dissolved gas exchange, controlled by blood flow across regions of varying concentration, is driven by the local gradient, that is, the difference between the arterial blood tension and the instantaneous tissue tension. Tissue response is modeled by exponential functions, bounded by arterial and initial tensions, and perfusion constants, lambda , linked to the tissue halftimes, tau , for instance, 1, 2, 5, 10, 20, 40, 80, 120, 180, 240, 360, 480, and 720 minute compartments assumed to be independent of pressure.

In a series of dives or multiple stages, initial and arterial tensions represent extremes for each stage, or more precisely, the initial tension and the arterial tension at the beginning of the next stage. Stages are treated sequentially, with finishing tensions at one step representing initial tensions for the next step, and so on. To maximize the rate of uptake or elimination of dissolved gases the gradient, simply the difference between arterial and tissue tensions is maximized by pulling the diver as close to the surface as possible. Exposures are limited by requiring that the tissue tensions never exceed M = M sub 0 + DELTA M d, as a function of depth, d, for DELTA M the change per unit depth.
If gas nuclei are entrained in the circulatory system, blood perfusion rates are effectively lowered, an impairment with impact on all gas exchange processes. This suggests a possible lengthening of tissue halftimes for elimination over those for uptake, for instance, a 10 minute compartment for uptake becomes a 12 minute compartment on elimination. Such lengthening procedure and the split elimination gradient obviously render gas uptake and elimination processes asymmetric. Instead of both exponential uptake and elimination, exponential uptake and linear elimination response functions can be used. Such modifications can again be employed in any perfusion model easily, and tuned to the data.

correct?

 

[cdennyb]

quoting someone else to substantiate your position is not wrong. If you feel my quotes are not necessary, why quote some web site with basic lung theory which in no way really relates to our discussion here of being horizontal when decompressing?

 

[JeffG]

Multitissue models, variations of the original Haldane model, assume that dissolved gas exchange, controlled by blood flow across regions of varying concentration, is driven by the local gradient, that is, the difference between the arterial blood tension and the instantaneous tissue tension. Tissue response is modeled by exponential functions, bounded by arterial and initial tensions, and perfusion constants, lambda , linked to the tissue halftimes, tau , for instance, 1, 2, 5, 10, 20, 40, 80, 120, 180, 240, 360, 480, and 720 minute compartments assumed to be independent of pressure.

In a series of dives or multiple stages, initial and arterial tensions represent extremes for each stage, or more precisely, the initial tension and the arterial tension at the beginning of the next stage. Stages are treated sequentially, with finishing tensions at one step representing initial tensions for the next step, and so on. To maximize the rate of uptake or elimination of dissolved gases the gradient, simply the difference between arterial and tissue tensions is maximized by pulling the diver as close to the surface as possible. Exposures are limited by requiring that the tissue tensions never exceed M = M sub 0 + DELTA M d, as a function of depth, d, for DELTA M the change per unit depth.
If gas nuclei are entrained in the circulatory system, blood perfusion rates are effectively lowered, an impairment with impact on all gas exchange processes. This suggests a possible lengthening of tissue halftimes for elimination over those for uptake, for instance, a 10 minute compartment for uptake becomes a 12 minute compartment on elimination. Such lengthening procedure and the split elimination gradient obviously render gas uptake and elimination processes asymmetric. Instead of both exponential uptake and elimination, exponential uptake and linear elimination response functions can be used. Such modifications can again be employed in any perfusion model easily, and tuned to the data.

correct?

Quoted from www.abysmal.com/ftp/abyss_V230_manual.pdf

Too funny.

Why don't you give credit to the people that actually write the stuff?

LOL