What's the end?

[bosshog]

If I calculate the nitrogen I get an EAD. What about 02? How do I calculate to find the END? Please help.

 

[rongoodman]

That depends on whether or not you consider O2 to be narcotic. There's some controversy, but many currently do. If so, for Nitrox, the END is just the actual depth. If not, it's the same as the EAD.

 

[Superlyte27]

Uh, no...The END is the same as the depth only for Nitrox mixes. For Heliox or Trimix the END is not the depth.

 

[bosshog]

I can calculate EAD....but that does not consider the O2. V-planner comes up with an END for helium mixes. I want to know the math behind it. O2 is supposedly more narcotic than nitrogen, but we also metabolize some of it. Does anyone have a formula for me?

 

[PfcAJ]

END for nitrox mixes = your depth. There's nothing 'equivalent' about it.

 

[rongoodman]

Uh, no...The END is the same as the depth only for Nitrox mixes. For Heliox or Trimix the END is not the depth.

I know, which is why I said "For Nitrox". I didn't think the OP was asking about helium mixes.

 

[TSandM]

There is no equation, to my knowledge, that makes any distinction between the degree of narcotic potency of oxygen and that of nitrogen. You simply decide whether you believe oxygen is narcotic or not. If so, your END on Nitrox is the same as your depth. If not, it's the same as your EAD. Most agencies now, I believe, are teaching that oxygen is narcotic, which makes things easy.

Once you add helium, you have to do the calculations.

 

[rjack321]

I can calculate EAD....but that does not consider the O2. V-planner comes up with an END for helium mixes. I want to know the math behind it. O2 is supposedly more narcotic than nitrogen, but we also metabolize some of it. Does anyone have a formula for me?

Nobody considers O2 more narcotic the N2. Yes its more lipid soluble. But the Meyer-Overton relationship is not a mathematical correlation you can actually use to figure out a narcotic potency for O2 since as you note there's metabolism too. Hence most people just consider O2 = N2 as far as narcosis is concerned. The other camp (slightly rarer) doesn't consider O2 to be narcotic at all.

 

[bosshog]

O.k.

Planning a dive to 150ft.
Back gas is trimix 21/35.
Nitrogen is .44*.79/183(ata)-33=69ft EAD.

If I plan this dive with V-planner it give me an EAD of 69ft but an END of 86ft.

I am assuming that it is adding some factor of O2 being narcotic. I was hoping someone could help with the math.
How do you usually plan for a dive like this? Do you assume and END of 69' or go by V-planner and assume an END of 86'?
Or do you have a different method altogether?

 

[rongoodman]

5.55ATA*.65(the combined fractions of the N2 and O2)=3.6ATA of narcotic gases=86' END

I assume O2 to be narcotic and do the calculation as above.