Tissue chart still high long after diving

[underwatermatt]

Is there a default tissue load on the shearwater graphs or can anyone think of a reason my tissue charts would be this high after 6 days out of the water? Even after a long dive trip (5 weeks, ~2-5 dives a day) there’s no way I would have this much residual nitrogen. Also, why would all compartments be equal? It seems to default to that even after an afternoon/ night out of the water, when I would think the fast compartments should be empty and the slow compartments still have a bit. Side note, but does anyone know how to pull the old tissue graphs out of the computer’s memory? I have a few dives I would be curious to see (yes I know it’s a theoretical model that means little but I want to see if the model matches with certain real world things)

 

[gmerick]

Looks normal to me.

 

[gmerick]

There is a good explanation in the user manual. The bars will go way toward the left on descent.

 

[broncobowsher]

That's not high, that's normal 1 atmosphere saturation.
The black like in the green band is the nitrogen loading.
The green band is the air you breath, at the pressure you are at (currently 1 atmosphere)
78% of what you breath is on the left of the black line, nitrogen.
21% of what you breath is on the right of the black line, oxygen.
The bars are all at the black line, your tissues are loaded to 78% Nitrogen.
The black line never moves in the green box unless you are breathing something other than air, bottom box is 50% O2 so the line is in the middle of the box. If you stayed there long enough all the bars would eventually stabilize at the black line again.

 

[Brett Hatch]

Don't think of the bands as coming off of the right side of the screen. Think of them as starting from the black line, and either going off to the left for ongassing, or going off to the right for offgassing.

The black line represents your tissues being in equilibrium with the gas you are breathing. Also known as being saturated with your breathing gas. When a band creeps to the left of the line, it represents tissues that are unsaturated, meaning that they are ongassing. When the band is to the right of the line, it represents tissues that are supersaturated, so they are offgassing. The red region at the far right is where the offgassing is too fast to be safe, and you are likely to be bent.

What you are looking at in that picture is, each tissue is at equilibrium with the gas you are breathing: air. No tissue is ongassing or offgassing, so they are all at the black line, as expected after 6 days above water. If you were to dip down a bit, the bands would go to the left. If you were to climb a mountain or hop into a plane, the bands would go to the right. Hope this helps.

 

[Kendall Raine]

Is there a default tissue load on the shearwater graphs or can anyone think of a reason my tissue charts would be this high after 6 days out of the water? Even after a long dive trip (5 weeks, ~2-5 dives a day) there’s no way I would have this much residual nitrogen. Also, why would all compartments be equal? It seems to default to that even after an afternoon/ night out of the water, when I would think the fast compartments should be empty and the slow compartments still have a bit. Side note, but does anyone know how to pull the old tissue graphs out of the computer’s memory? I have a few dives I would be curious to see (yes I know it’s a theoretical model that means little but I want to see if the model matches with certain real world things)

They are normal for surface saturation. They are all the same because, well, all your tissues are saturated at surface pressure. What do you think they should be? Suggest you review your understanding of how this graphic works.

 

[underwatermatt]

Thanks all for your responses! The way the graph was explained to me was apparently unclear and left me with a wrong understanding, I was lead to believe that the graphs would be empty at the surface after all off gassing is completed. This makes much more sense. And I guess I’m bad at reading manuals, since I somehow missed that nice colorful graph

Happy diving y’all!

 

[Gone for diving]

Even I learned something...
Makes total sense, once I think about it for more than 5 seconds

 

[underwatermatt]

Even I learned something...
Makes total sense, once I think about it for more than 5 seconds

Yup, once you think about it, it makes perfect sense

 

[rsingler]

For me, one important thing to remember is that the vertical black line changes instantly when you shift to a different gas.

Similarly, the green to yellow transition doesn't physically move, but the green area shown is potentially much "larger" at depth. That's why the diver who is completely saturated with N2 at the surface is only 1/3 as much saturated in the "after descent" graph.

Which, conversely, is why things bloom so much at shallow depth in the "last deco stop" graph, after you accumulate that extra N2 at depth.

Predicting where you'll peak is the true value of the SurGF metric, for which all divers owe Shearwater a debt of gratitude. Even if other mfrs are now copying it using a different name.