Quote:
| Originally Posted by JohnD what PPO2 do people use, I am having an argument with my DO as he wants to stick to 1.4 and I like 1.6 on deco stops. gets me out of the water quicker and I am usually nowhere near my 80% CNS for an individual dive. comments? pros and cons, please. |
I use 100% in the bags if my loading is anticipated to be less than 80%. I only start to sh1t my pants when CNS is expected to be a lot more than that.
Someone mentioned that the % of the gas is more important than the PPO for deco, I kind of agree. I would prefer full flush and use 100% at 6m, then ascend slowly to decrease the loading. At 6m the CNS loading is just over 2 (if my memory serves) and at 3m it is just over 0.5. If using 80% then you get the same loading at 6m as 100% is at 3m. It's the old gradient argument.
Oxygen is transported in the blood in two ways; dissolved in the blood (1.5%) and bound to hemoglobin (98.5%). The idea is to saturate the blood so the hemo binds to all 4 O2 molecules. Saturation increases with PO2 in a curvlinear fashion.
Now down to earth and decide how easy it is to get pure O2 at pressure in OC rigs and how restrictive it is when planning your dive (not many alternative plans available), MCCR it's a no brainer.
You might want to have another read of Anne Maries post, bit of wisdom in between those lines.
One more point to ponder, with all this talk earlier regarding the validity of CNS, I wonder how many Vestibular hits have been wrongly seen as CNS hits?