Residual Nitrogen Levels and their correlation to Air Consumption

[Butt Ugly Toad]

Dr. Deco,

Are you aware of any studies that have been done, or are being done, concerning air consumption rates and residual nitrogen? I believe a person's air consumption rate is proportional to their residual nitrogen levels. Some of the newer air integrated dive computers calculate air consumption but do not allow it to have any affect on decompression limits.

I believe this to be the "next phase" in dive computers and it will make dive computers more "personal" to the user. Plus, for those of us with very low air consumption rates, it will give us more non-decompression bottom time than the "air-hogs"!

Thanks,
Toad
AKA: George W. Shope

Ps: I base my calculations on the simple fact that the more you breathe, the more nitrogen you will asorb, as in the "Cold Water/Strenuous Conditions" stipulation of the RDP General Rules Section.

 

[DiverBuoy]

filling lift bags, air horns, BC/BP inflation deflation, dry suit. If the source is the same tank from which the calculations are being made - the numbers would be inaccurate.

Either way I did some research on this, and Suunto actually claims starting with the Cobra that some adjustment was made on breathing rate. I'll have to find it for you now.

Anyway Here is the PDF manual for the Suunto Cobra

 

[BRW]

Way off, BUT

You have the cart before the horse.

Consumption rates are proportional to metabolic needs,
NOT residual N2 (nor any other inert gas) in lowest order, and
as O2 and CO2 play off against each other in any activity. Inert
gas tensions in arterial, venous, and tissue domains (lower
than ambient by the inherent unsaturation) remain the same at
stasis. The O2 and CO2 tensions vary across each domain,
providing the necessary ingradient for O2 and outgradient
for CO2. Breathing slower or faster has virtually nothing
to do with inert gas levels, just O2 and CO2 levels, insofar as
metabolic requirements. For the same metabolic requirement,
O2 extraction and CO2 elimination are the same whether you
are an air hog or air virtuoso, at depth or at the surface. And
while inert gas tensions can be changing for any reason.
As metabolic needs change, blood flow and breathing rates
(consumption rates as you call them) respond accordingly.

Then inert gas tensions fall as they may, depending on pressure,
inspired gas mixture, diffusive properties of the lungs, existing
inert gas levels in arterial, venous, and tissue domain, presence
of bubbles in pathways, blood perfusion rates, etc. And not the
other way around.

As developer of Suunto, Mares, Hydrospace, Plexus, GAP,
ABYSS, Zeagle, etc. deco and computer algorithms, I need tell
you that reduction in NDLs has nothing to do with your belief,
nor consumption rates. Age, workload, and temp statistics
feed into calcs as safety factors and affect M-values, but
are not coupled to consumption rate as you fancy. So do
reverse profiles, short SIs, multiday diving, dual phase
kinetics, deep stops, Doppler, and other related factors. None
of which couple air hogs to larger residual N2 (or He). Nor vice
versa.

But being an air virtuoso certainly has other benefits.

Regards,

 

[pops]

what are the biological mechanics underlying the relationship between age and deco limits, anyway? the reason i ask is i'm 57 years old and N absorption is something you have to think about because you certianly can't feel it happening until too late.

 

[Diver0001]

pops once bubbled...
what are the biological mechanics underlying the relationship between age and deco limits, anyway? the reason i ask is i'm 57 years old and N absorption is something you have to think about because you certianly can't feel it happening until too late.

In a word, circulation.

R..

 

[Dr Deco]

Dear B.U. Toad:

Air Consumption

The body can dissolve about one quart of nitrogen per atmosphere of pressure (Henry’s Law) at saturation. Considering the number of quarts of air in a SCUBA tank, it is obvious that virtually all of it is exhaled during a dive. Thus, air consumption is really not a factor.

Oxygen Consumption

Oxygen consumption is a different matter, as it indicates the work being performed by the muscles and, more importantly for diving, the blood flow to carry that oxygen to these tissues. This oxygen loss is not what is being measured with air consumption monitors, however. There are currently no available devices for divers to use in the field. In addition to oxygen consumption, we have the “muscle pump” that assists to movement of blood in tissues; this is a local mechanism.

Oxygen uptake measurements of this nature are performed at NASA to study efficient decompression procedures, but this is some distance away from a field-useable technique.

Decompression Algorithms

In whatever way you may calculate gas uptake and elimination, two factors play a role. One is that the halftimes are immutable with activity. An active diver will have halftimes of 5, 10, 15, 20 …, 350, 450 minutes and a resting, phlegmatic one will have halftimes of 5, 10, 15, 20 …, 350, 450 minutes - - same ones. Current systems (other than a variant of the NASA one) do not allow for modification. Secondly, long halftimes are derived from admixtures of lipid (fat) and aqueous (watery) tissues. These “mixtures” will not change since they are derived from anatomy.

Older Divers

There does appear to be a difference in DCS susceptibility in older divers. As mentioned above, this is probably the result of circulation. It just slows down.:turtle:

Dr Deco :doctor: