Posted by Karl S. on January 28, 2003 at 15:32:07:
In Reply to: There is also bradycardia posted by seahunt on January 28, 2003 at 14:16:31:
There is a whole lot more to purging CO2 than just from your lungs.
Part of the fallacy of gearing up at your car and making the long haul down to the water all geared up is that youre building up CO2 in your blood and muscles as well.
Buy the NAUI booklet about breathhold diving, and it will go into really deep detail about the lengthy amounts of time that freedivers spend purging CO2 before an immersion, and the underlying theory for doing it.
If you then try that with scuba, you will also find, as have I and others, that you are less susceptible to narcosis at depth, for some reason. The reason is probably because CO2 loading is more of a major factor in narcosis than it have ever been given credit.
seahunt(small-S) is also correct about the mammalian diving reflex. While you are face down in the water relaxing and breathing deeply to purge CO2 before your dive, you will allow a longer time for the mammalian diving reflex to be triggered, aka bradycardia.
So less narcosis and less air consumption due to first CO2 purging before you descend for scuba. But this is not taught in the mainline teaching programs of any of the agencies, at least not until you get to the instructor level, and even then a lot of the advanced concepts are still not incorporated into the regular teaching programs yet for basic open water scuba.