GFHi - practical meaning?

[J-Vo]

I assume y will be my desired ISS result.

"y" would be your instantaneous super saturation at any moment in time(x). ISS would be the sum of all your "y"s for the entire dive and until you normalize with ambient post dive (6 halftimes of the tissue).

 

[NAM001]

IMO surfGF and GFhi has no ralationship except under one condition. that being when you dive until NDL hit zero. GF Hi is a limit not a status surf GF is a status and not a limit.

 

[rsingler]

IMO surfGF and GFhi has no ralationship except under one condition. that being when you dive until NDL hit zero. GF Hi is a limit not a status surf GF is a status and not a limit.

The spreadsheet from EFX is currently displaying, not GF99 nor SurGF, but supersaturation in ATA. Thus, a status.
If we can use the supersaturations at certain timepoints, and "compute the area under the curve", we might be able to get a handle on supersaturation stress for a given profile.

 

[dmaziuk]

It's simply a measure of the total supersaturation exposure for the entire dive profile. In the paper you reference they look at the integral supersaturation of the two different compartments and how it changes with respect to the 504,271 hypothetical dive profiles.

Care to try coding that statement in a programming language of your choosing?

 

[dmaziuk]

The spreadsheet from EFX is currently displaying, not GF99 nor SurGF, but supersaturation in ATA. Thus, a status.
If we can use the supersaturations at certain timepoints, and "compute the area under the curve", we might be able to get a handle on supersaturation stress for a given profile.

For no-stop dive you could just do it upon surfacing. It still skims over the issue of different tissues tolerating different overpressures. Taking it at the surface rather than at SS should filter out the fast tissues, and slow tissues won't contribute much, so maybe it'll show something useful...

 

[njdiverjoe]

Care to try coding that statement in a programming language of your choosing?

I could in a handful of languages -- but it wouldn't be of any use if it wasn't integrated with whatever software is simulating the profile.

Additionally -- I don't believe you will glean any new information in looking at ISS for no-stop profiles. If you want to reduce your risk then slow your ascents as you get closer to the surface, extend you safety stop, etc

 

[EFX]

What is "integral supersaturation" anyway?

If we have a series of x,y data points plotted on a graph with x being time in minutes from 0 to the dive duration and for each x, y is the tissue pressure then we can draw a line between all the data points. The integral supersaturation is the area under the line. If we can come up with an equation to represent our line of data points and integrate with respect to time then we can find the integral supersaturation. The y data points can be all the leading TC's or all the TC pressures throughout the dive or anything else we want to graph. Here's a simple example:

Say we have a graph of a straight line at y = 4 and extending from x = 0 to x = 8. If we draw this line and add a verticle line at x = 8 which connects to the horizontal line going through y = 4 then we've got a rectangle of the coordinates (x,y): (0,0), (0,4), (8,4), and (8,0). The equation for our horizontal line is: y = 4. If we integrate this function of y with respect to x over the limit from 0 to 8 we could write: y = Int4dx (I'm using Int for the integral symbol). Solving this equation yields the equation y = 4x and substituting the limit of 8 into x yields 32 as the area under the graphed line.

 

[rsingler]

If you want to reduce your risk then slow your ascents as you get closer to the surface, extend you safety stop, etc

That's exactly what we're trying to quantify in this thread: Recreational Ascent Rate in the last 15 feet
It seemed intuitive, but proving it is elusive.
Looking at GF99 as you rise the last 15 feet gave a hint of the changes, but since @Dr Simon Mitchell has used ISS as a measure of decompression stress in other studies, I wondered if it could be applicable as a measure of whether or not an ultra-slow final ascent is worth the time, compared with say, just extending your safety stop.
But I don't want to derail this excellent separate discussion...

 

[Jay]

There's a bit about ISS in this thread with some calculations and graphics done by Kevin #255 NEDU Study

Perhaps a new thread about ISS is needed?

 

[dmaziuk]

Looking at GF99 as you rise the last 15 feet gave a hint of the changes, but since @Dr Simon Mitchell has used ISS as a measure of decompression stress in other studies, I wondered if it could be applicable as a measure of whether or not an ultra-slow final ascent is worth the time, compared with say, just extending your safety stop.

So what you want then is to take sum( Pinsp - Pamb ) across all tissue compartments at the end of safety stop, and then again: at the surface, and compare the two.