FRV / FRC / Exhale diving

[ADR]

The answer to the puzzle:

If one has a strong DR that continues for some time after one resumes breathing again then the muscles are still maintained underperfused and hypoxic, which would be equivalent to them incurring an even longer breath-hold. The converse being true for divers with a weak response.

What this means is that DR is an absolute prerequisite for extreme dives.

Cheers,
Seb

 

[ADR]

In case anyone is wondering why I am speaking for Seb......I'm not! He has been down in Sydney staying with me and used my PC

 

[cdavis]

Dr. Lindholm recently published an paper that, among other things, showed "reverse co2 transfer" as depth increased, ie, co2 goes from the lungs to the blood during a dive, as depth and preasure increase (see thread, SWBO, all lies) If so, wouldn't FRC diving substaintially reduce blood acidity relative to full lung diving?? Does that show up in time to onset of the urge to breath and lowered resistance to BO as lower blood acidity leads to slower disassociation of 02 from heamaglobin?

Connor

 

[efattah]

Connor,

What you are describing is true, and the result (in my experience) is dramatically decreased CO2 narcosis while doing FRC dives.

 

[sebastien murat]

Metabolic and haemodynamic factors interact in complex ways. Sometimes it is inappropriate to have excessive acidity, as in the working muscle tissue, since it can result in rapid hypoxemia in vital organs. So, though it may seem to be an advantage to keep the muscles aerobic it may come at an unacceptable cost. On the other hand, a stronger vasoconstriction, induced by FRC, may aid in redistributing blood flow away from such O2 hungry tissue, and towards more vital organs. Moreover, because of the prompt vasoconstriction there is better thermal insulation which would better maintain blood temperature, which in turn would aid in O2 desaturation in vital organs. Furthermore, some very recent tests on my self showed that although FRCs resulted in absolutely lower end-dive CO2 tensions (i.e., reduced urge to breathe) this could have been, in part, due to the rather low metabolic rate I experience during diving; evidenced by the comparatively elevated end-dive O2 tensions.
But, as I said before, I think the problem is much more complex than we probably appreciate.

Seb

 

[cdavis]

Thanks guys, this FRC stuff is getting more interesting all the time.

Connor