scubadobadoo:Not if I am "back on the boat BEFORE" the nitrox diver as I stated. That means that my dive was shorter.
You could deco with 50% and cut 2 minutes off your short dive time and come out as clean as the long dive Nitrox diver.
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You could deco with 50% and cut 2 minutes off your short dive time and come out as clean as the long dive Nitrox diver.
scubadobadoo:That means that my dive was shorter.
Which is why you should be diving with Nitrox instead of Air.
JeffG
Contributor
????? You sure about that.TheRedHead:
JeffG:
The diffusion gradient. :shakehead
More interesting stuff:
The pressure of gas dissolved in tissues is termed tension. The sum of the partial pressures of the free gases inside a bubble adds up to the total internal pressure of the bubble. The Bubbles will grow or shrink, depending on whether the gases in the surrounding tissue sum to a tension T that is greater or smaller than the bubble's internal pressure P(BUBBLE). In either case, a pressure gradient G = (T - PB) across the skin of the bubble drives the flow of gas.
When G is positive, tissue tension is greater than bubble pressure, leading to bubble growth by inward flow of gas. G is negative if tissue tension is less than bubble pressure, leading to bubble shrinkage by outward flow. The objective of bubble models is to keep G negative (or zero) by appropriately setting ascent stage depths and choosing gas mixtures to encourage bubble out gassing to tissues. The deep stops of the bubble models keep P(AMBIENT) large, which in turn keeps P(BUBBLE) large and G negative to force out gas. By choosing ascent gases that "open the oxygen window" as wide as possible and as early in the ascent as possible, tissue tension is reduced, helping to keep G negative. The VPM and RGBM treat tissue tensions just like the neo-Haldane models. The rate of In gassing and out gassing of dissolved gas is modeled as an exponential rate equation.
The pressure of gas dissolved in tissues is termed tension. The sum of the partial pressures of the free gases inside a bubble adds up to the total internal pressure of the bubble. The Bubbles will grow or shrink, depending on whether the gases in the surrounding tissue sum to a tension T that is greater or smaller than the bubble's internal pressure P(BUBBLE). In either case, a pressure gradient G = (T - PB) across the skin of the bubble drives the flow of gas.
When G is positive, tissue tension is greater than bubble pressure, leading to bubble growth by inward flow of gas. G is negative if tissue tension is less than bubble pressure, leading to bubble shrinkage by outward flow. The objective of bubble models is to keep G negative (or zero) by appropriately setting ascent stage depths and choosing gas mixtures to encourage bubble out gassing to tissues. The deep stops of the bubble models keep P(AMBIENT) large, which in turn keeps P(BUBBLE) large and G negative to force out gas. By choosing ascent gases that "open the oxygen window" as wide as possible and as early in the ascent as possible, tissue tension is reduced, helping to keep G negative. The VPM and RGBM treat tissue tensions just like the neo-Haldane models. The rate of In gassing and out gassing of dissolved gas is modeled as an exponential rate equation.
JeffG
Contributor
A nitrox diver isn't changing gases.TheRedHead:
Off gassing for a nitrox diver is based on change of depth, that creates a partial pressure difference, which means the tissues try to match this...ergo...on/off gases.
The tissues determine the speed, the gradient determines which way the gas goes.
mccabejc
Contributor
scubadobadoo:
Well, maybe. As I mentioned elsewhere, I think that's an assumption based upon our reading of the DAN statistics, which address the general dive community, not you in particular. Whether it has anything to do with any one of us and our particular physical condition, etc., on the day of the dive we have no idea.
Statistics are one way of saying "I have no idea what the answer is for you, so I'll just give you a bunch of historical data for a bunch of other people that may or may not be applicable".
So it's all opinion. Nobody is right, and nobody is wrong. Nobody can come close to proving that nitrox will or won't prevent DCS in any of their dives. So we're left with some folks figuring that less nitrogen is better, and others who say that less nitrogen doesn't make much difference.
But the topic is always good for an unending argument...
JeffG:
I said initially that it depends on the length and depth of the dive as to which compartments will load and unload at at which rates during and after the dive. Nonetheless, the partial pressure of nitrogen in EAN32 will always less than the partial pressure of nitrogen in air.
You will achieve the change of depth (thus pressure) as you surface. That's a given, don't you think?
limeyx
Guest
TheRedHead:
I dont pretend to know all the answers, but if you deco on back gas, then it's (as JeffG said) the difference in pressure between the insipired N2 and the N2 in the tissues. This difference is based on depth change.
if you change gas (from air to 50% nitrox) then you get a second effect as you change the amount of inspired N2 (decrease in this case) -- what some call the oxygen window.
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