normoxic/Hypoxic diffrences

[HammerNoMore]

Just to clarify, several posts mention normoxic as being 21% O2. This is not the way I've seen the term used, at least medically. From what I understand a normoxic mixture for a given depth would have the same oxygen concentration as air does at the surface.

 

[vodolaz]

Normoxic is 21%. The percentage of a gas in a mix doesn't normally change during the dive.

 

[H2Andy]

The percentage of a gas in a mix doesn't normally change during the dive.

no, but the partial pressure does. 100% O2 is fine at the surface, but is toxic
past 20 feet. what i think James is saying is that if the PO2 is similar to air at the
surface, regardless of depth, then its normoxic.

so.. basically... if the P02 at the intended depth is 1.4 to 1.6, then basically
James is calling it normoxic.

 

[vodolaz]

no, but the partial pressure does. 100% O2 is fine at the surface, but is toxic
past 20 feet.

Right, but he referred to the concentration of a gas within a mix (FO2 in this case), not the PPO2.

 

[H2Andy]

oh... i thought he was talking about partial pressure

 

[wedivebc]

Just to clarify, several posts mention normoxic as being 21% O2. This is not the way I've seen the term used, at least medically. From what I understand a normoxic mixture for a given depth would have the same oxygen concentration as air does at the surface.

I often dive rebreather so my fraction of O2 changes during the dive. I manually adjust my mixture to give 1.3 po2 at any given depth except near the surface where I back off to around .7
It would not be practical to dive a mix that gave you (on open circuit) a po2 of .21 (21%) at depth because it would quickly become hypoxic near the surface. When referring to normoxic and hypoxic, these terms are meaningless except in regards to the training level required to use them. Trimix divers seldom refer to their mixes that way and it is just another example of divers jargon that has permeated this sport.

 

[HammerNoMore]

Right, but he referred to the concentration of a gas within a mix (FO2 in this case), not the PPO2.

Concentration, as I am refering to it is the number of molecules per unit, not a percentage.