Rising GF99 after surfacing???

[rjack321]

The drop in GF? Or the drop in bubbles? Or the drop in risk?

Increase in bubbles, increase in risk. Your peak DCS risk is not the minute you surface. Most DCS cases manifest 30 to 120 minutes after surfacing.

 

[L13]

Increase in bubbles, increase in risk. Your peak DCS risk is not the minute you surface. Most DCS cases manifest 30 to 120 minutes after surfacing.

Yes.

But in your previous comment:

Maximum bubbles scores are 30mins to 2hrs after surfacing depending on the dive and which tissues are loaded. So the drop is actually rather fast/abrupt.

You said "So the drop is actually rather fast/abrupt." What were you referring to that was dropping?

 

[rjack321]

Yes.

But in your previous comment:

You said "So the drop is actually rather fast/abrupt." What were you referring to that was dropping?

the GF99 drop in the software after a few minutes is "fast" compared to the reality which is your bubble scores and DSC risk which are rising for 30+minutes after surfacing. My point is even if the GF99 rising after surfacing that's accurate/consistent with DCS risk. The fact that it declines a few minutes later is actually too fast and inconsistent with DCS risk.

 

[rsingler]

@rjack321 brings up a good point.
We should all keep in mind what he just said.
I look at the max GF99 as just an  index of my risk. But as he says, your bubble index increases significantly at 30-45 min, and is aggravated by exertion, for example. I try to just sit and relax as much as possible after the second deco dive of the day. Lugging tanks is exactly the opposite of what I want to be doing.
It's a subject for another thread, but maybe leading compartment GFHi is not the ideal universal marker. Since we know that faster compartments seem to be more tolerant of overpressure, maybe we need to be identifying the GFHi in specific slower compartments for longer or repetitive dives. Even if leading compartment GFHi is <70 after a big dive, should we be looking at GFHi > 50 in some yet-to-be- determined slow compartment as a closer correlate with DCS?
We all bubble, but we don't all bend. Our lungs filter out 99% of the venous bubble load, and along with PFO's, we seem to focus on intra-pulmonary shunting as a cause for some bad outcomes. But what if there's bubbling in slow tissues that's picked up on the arterial side, causing more prosaic joint DCS?
So much yet to learn...

Until we know more, I want to know my calculated maximum GF99. Hence, this thread and my concern about (by me) an unnoticed rise in max GF99 that appears in my graphs.

 

[L13]

the GF99 drop in the software after a few minutes is "fast" compared to the reality which is your bubble scores and DSC risk which are rising for 30+minutes after surfacing. My point is even if the GF99 rising after surfacing that's accurate/consistent with DCS risk. The fact that it declines a few minutes later is actually too fast and inconsistent with DCS risk.

GF99 is a calculation of tissue supersaturation, not bubble scores or immediate DCS risk. It has a defined meaning that should not behave that way.

 

[L13]

@rjack321 brings up a good point.
We should all keep in mind what he just said.
I look at the max GF99 as just an  index of my risk. But as he says, your bubble index increases significantly at 30-45 min, and is aggravated by exertion, for example. I try to just sit and relax as much as possible after the second deco dive of the day. Lugging tanks is exactly the opposite of what I want to be doing.
It's a subject for another thread, but maybe leading compartment GFHi is not the ideal universal marker. Since we know that faster compartments seem to be more tolerant of overpressure, maybe we need to be identifying the GFHi in specific slower compartments for longer or repetitive dives. Even if leading compartment GFHi is <70 after a big dive, should we be looking at GFHi > 50 in some yet-to-be- determined slow compartment as a closer correlate with DCS?
We all bubble, but we don't all bend. Our lungs filter out 99% of the venous bubble load, and along with PFO's, we seem to focus on intra-pulmonary shunting as a cause for some bad outcomes. But what if there's bubbling in slow tissues that's picked up on the arterial side, causing more prosaic joint DCS?
So much yet to learn...

Until we know more, I want to know my calculated maximum GF99. Hence, this thread and my concern about (by me) an unnoticed rise in max GF99 that appears in my graphs.

I disagree. GF99 is a calculation of current supersaturation. GF99 at surfacing is the supersaturation at surfacing and should directly correlate with peak bubble index 30-45 minutes later. In other words, it is a measure of the driver of bubbles and DCS, and therefore is a good measure of risk of bubbles and DCS to come. It's big advantage is that it is calculable. While bubble scores can be measured they can not be calculated.

GF99 is dropping while bubble scores are going up over the next 30-45 min because the supersaturation represented by GF99 is the source of the gas in the bubbles later. Max GF99 is therefore useful in estimating the max bubbles and the DCS risk.

If GF99 is as defined by Shearwater documentation, it should not behave as observed in your plots.

 

[rsingler]

Both can be true. I agree that GF99 should not increase after surfacing. I agree that the increase in bubbling at some time after surfacing is not in any way related to this (spurious) increase in graphed GF99. I agree that currently, leading compartment GFHi is the best index we have for trying to predict DCS risk.
But since we all bubble, and yet don't all bend, there is a factor that is yet to be fully understood. When the Spisni study started to confirm what was suggested about bubble models vs  ongassing in slower compartments during deep stops, we began to learn that it's not a simple function of total N2 load, much less theoretical bubble diameter.

I wonder whether time will reveal a better DCS correlate than leading compartment GFHi, particularly one that might lend more weight to slower compartments. Mere speculation...

 

[L13]

Both can be true. I agree that GF99 should not increase after surfacing. I agree that the increase in bubbling at some time after surfacing is not in any way related to this (spurious) increase in graphed GF99. I agree that currently, leading compartment GFHi is the best index we have for trying to predict DCS risk.
But since we all bubble, and yet don't all bend, there is a factor that is yet to be fully understood. When the Spisni study started to confirm what was suggested about bubble models vs  ongassing in slower compartments during deep stops, we began to learn that it's not a simple function of total N2 load, much less theoretical bubble diameter.

I wonder whether time will reveal a better DCS correlate than leading compartment GFHi, particularly one that might lend more weight to slower compartments. Mere speculation...

We bubble because of supersaturation. It should be no surprise that supersaturation is useful in predicting bubbling and DCS.

on gassing --> increased saturation at pressure --> supper saturation at lower pressure --> bubbling --> DCS.

 

[inquis]

supper saturation at lower pressure --> bubbling --> DCS.

I believe @rsingler 's point is that bubbling does not always lead to DCS. (In fact, it SELDOM does.) In other words, supersaturation is a necessary but not a sufficient condition; and therefore, surfGF is not the whole story. I tend to agree.

 

[L13]

I believe @rsingler 's point is that bubbling does not always lead to DCS. (In fact, it SELDOM does.) In other words, supersaturation is a necessary but not a sufficient condition; and therefore, surfGF is not the whole story. I tend to agree.

I agree with that. However, supersaturation does seem to correlate fairly well (better than anything else we have so far) with DCS risk. In fact, I seem to remember that it correlates better than bubble scores.

My theory for that is that bubble scores are a measure of bubbles where they are not dangerous in the body(heart and major blood vessels), While supersaturation accounts for effects everywhere in the body including capillaries and non-circulatory tissues.

If you can do all your bubbling where it doesn't matter, then you are good!