lung volume measured, +3 litres with packing

[efattah]

I have also had the weird voice effect after static.


Eric Fattah
BC, Canada

 

[smellsfishy]

Eric,

Thanks for the follow up ! That's a much larger variance than I expected.

 

[fpernett]

That weird voice effect probably is due to swollen of vocal cords in the effort to keep glotis closed.
I wasn't a packer, but due to my brother insistence I started. The first statics I made with full pack ended very early and with that weird voice, so I made a ENT specialist friend of mine to make a indirect laringoscopy before and after a forceful full pack static apnea, and he noticed my swollen vocal cords after that.
My static has not improved because I think it takes time to get used to that lung volume, but now I make what I use to make without packing so think I'm improving.
One technique to avoid that uncomfortable feeling is to displace the abdomen forwards, that reliefs the pressure.

 

[Pezman]

Effect of RQ on buoyancy

A bit off topic, but is this calculation right?

Assume that you are an elite freediver and you can pack to 10L.
After 3:30, you have used up less than 20% of your O2 (i.e. your paO2 os over 80%).
You are fond of bacon, scrapple etc., and have an RQ of almost 0.7
The air you breathe is 20% O2

After 3:30. your change loss in volume due to RQ should be:

10L * (100%-80%) * 20% * 0.7 = 0.28L

So a little over half a pound, even in a pretty extreme example.

I think that I get shifts on the order of a half-pound or more under far less extreme conditions. Does this suggest the change in volume is mostly due to C02 going into solution?

 

[efattah]

Keeping in mind that the amount of nitrogen in the lungs will remain constant, then here are some numbers to think about for one of my long statics:

I inhale 20% O2, 80% N2
Initially my lung CO2 level is 3.0%
At the end of the static my lung CO2 level is 6.2%
At the end of my static I exhale 4% O2
So, at the end of my static, my lungs are 10.2% (O2+CO2), and the remainder must be nitrogen, 89.8%.

But, in litres, the amount of nitrogen remained constant. So, given that I started with 80% N2, and finished with 90% N2, then:

Initial state:
Total Volume of N2 / Total Lung Capacity = 80%
TVN2 / TLC(i) = 0.8
or
TVN2 = 0.8 * TLC(i)

Final state:
Total Volume of N2 / Total Lung Capacity = 90%
TVN2 / TLC(f) = 0.9
TVN2 = 0.9 * TLC(f)

But, the total volume of N2 is the same, so, dividing the two equations:

1 = (0.8/0.9) * (TLC(i)/TLC(f))
0.9/0.8 = TLC(i) / TLC(f)
TLC(f) / TLC(i) = 0.8 / 0.9 = 88.8%

So, my lung volume has been reduced to 88.8% of its initial volume. If I started with FVC = 10L, RV = 2L, TLC = 12L, then 0.888 * 12 = 10.656L

So, 1.35L of air volume has disappeared by the end of the apnea, which would correspond to 1.35kg of buoyancy.

My calculations have neglected the water vapour which saturates the air you inhale.

Eric Fattah
BC, Canada

 

[Aquagenic]

Dang Eric,
You are truly the master. To do it is one thing, to know the math is another. My respects to you.

 

[Pezman]

I'll have to work those equations, but at a glance it looks like many more moles of O2 went in than moles of C02 came out, so I think that the upshot of what you are saying is that the loss in volume is dominated by CO2 that went into solution. No surprise since Co2 is 22x more soluble in water than O2 (in fact, CO2 in solution is the main transport mechanism for Co2 exchange, isn't it?). I kind of suspected that Co2 into solution was the main culprit. BTW, nice touch putting RV in as part of the calc.

I'll have sit down tonight and look into what Henry, Fick and Graham say on the matter -- mostly because I have an incredibly bizarre sense of what's fun. btw, this page is great for finding relevant gas laws -- and lot's of other physical science info http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/henry.html#c3.

It would be interesting to relate the observed effects to what's predicted by these equations. I think that using Hanry's Law to relate partial pressure of Co2to the number of moles of gas that are "missing" can be used to estimate a "water equivalence" of the body, using an assumption that the liquid <-> gas exchange is approximately at steady state. Graham's law could be used to check on how big a lag to expect (hopefully negligible). I realize that circulation, metabolism, ongoing diffusion etc. make this a anything but a steady state system, but it would be nice to see where a first-order approximation lands.

Anyone got suggestions on a realistic range of RQ's to use for a calc like this? Hopefully something narrower than 0.7 to 1.0.

 

[Bill]

Let me throw some numbers into the hat. In trying to adjust the depth for neutral buoyancy, funny things happened. I have a theory.
When you leave the surface the lungs are about 4% CO2, 18% O2 and 78% N2 (just a guess). When you surface it is 6, 4 and 90 or 5.5, 4.5, 78 and 12% lost when compared to original volume. This worked out close to the calculations for surface measurements and end of dive figures but when I pulled down to 16 meters to check, I was heavier than estimated. Now for the theory.
When you start a dive, half the useable oxygen is in the lungs but the body uses lung O2 to maintain blood saturation near max. At one minute into a free immersion, I had only used about 25% of my total O2 but it was 50% of my lung O2 and if it was too soon for CO2 to replace the lung volume then I would lose 10% of my lung buoyancy. In Eric's case, it would be about one kilo in the first minute and less than 1.5 kilos in 5 min.
Measurements are close but I freely admit that this is lousy science. What do you think?
Aloha
Bill
P.S. I now use descent/ascent times and velocity of free fall to adjust my ballast.

 

[Walrus]

Hi Bill,

I don't see how your lungs only hold half the available oxygen. It's definitely not in my case. If that were true when I do say a full exhale dive, I would have %50 + .25 x%50, so say %63 compared to the oxygen of a full inhale. With the rapid bradycardia and vasoconstriction you get on exhale compared to inhale I don't think your body burns the O2 quite as fast. If I compare my exhale times to inhale, say for a warmup to 15m it's about 1.40 compared to about 4.00 if I pushed it a bit. And I don't even pack on my inhale warmups. So my exhale time is about %41 compared to my inhale. + on the inhale I burn O2 faster.

When I do dry statics I get pretty close to half for an exhale compared to inhale. ie say 3.15 compared to 6.30 (no packing). When I have hooked up to a pulse oximeter my blood O2 drops real quick on an exhale static, and so does my heartrate. So again I think that during the exhale static I burn O2 a bit slower. So still only %50 of the time when it should be more then %63. When I add packing to the equation my total lung O2 is another %36 higher.

I realize I'm not being very scientific and everyone’s exhale vs inhale times will be different. Most people I dive with have even a much higher ratio of inhale time vs exhale time then me. I was just doing a real rough comparison of figures to get an idea. I train with a doctor and he (only roughly) worked out for an average person it's probably closer to %33 O2 stores in the blood and %67 in the lungs. To me that makes sense. My guess has always been the same, say 1/3 blood vs 2/3 lungs.

You can argue that good freedivers will have more hemoglobin so more O2 in the blood. But then again they also pack and have much larger O2 stores in the lungs also. Eric or anyone else got a more scientific answer ?
I'm actually interested to know now.

P.S. I'm really only comparing statics as trying to work out muscle O2 stores and deep dives just get too darn complicated. :hmm

Cheers,
Wal

 

[Bill]

Very interesting Wal. I used a quote from the good doctor that was in a heated discussion about FRC dives last month. That gives a figure of close to 40% for the lungs and the fact that my best full exhale is over 50%.

"Rahn (1964) nicely summed up the human situation: a 70kg man at TLC 5.5L and a PAO2 of 120mmHg (which is generous) has a total store of 1996ml: 880ml in the blood, 820 in the lung, 240 in myoblobin, and 56 in physical solution."

If I could do a 60+ CBNF like some people I know, I'd just dive and leave this stuff for old men ;-)

Aloha
Bill

 

[efattah]

When you actually dive, the situation is further complicated by the pressure. Under pressure, nitrogen now also dissolves into the body fluids, CO2 is far more soluble, and even oxygen begins to dissolve into the plasma, all of which contribute to decreased lung volumes...

Now, if someone could actually do the calculations and calculate the volume of nitrogen absorbed into body fluids on a single dive to x metres for y minutes... that would be very useful for freediving deco models.

Eric Fattah
BC, Canada

 

[Ulf]

Rahn (1964) nicely summed up the human situation: a 70kg man at TLC 5.5L and a PAO2 of 120mmHg (which is generous) has a total store of 1996ml: 880ml in the blood, 820 in the lung, 240 in myoblobin, and 56 in physical solution."

My readings, normal:-
VC = 6.7L and TLC = 8.4

with max packing it was
VC = 9.6L and TLC = 11.4

This is interesting. Let's say Wal weighs 70kg but with those huge lungs he would have 52% of his O2 in his lungs at normal TLC and with packing 59%. And that seem to be close to the percentage of his static times...

/Ulf

 

[Walrus]

Hi Bill,
I get it now, that's pretty close to what my doc friend worked out. The thing that you didn't acount for is Useable O2 stores vs Actual O2 stores. You cannot use %100 of the O2 in your lungs, but you use a lot. Eric said he got down to %4 ?

Now look at the blood O2 store, when most people get down to say %50 SaO2 they would blackout. So the limit for the above example is 440ml blood O2 that can be used not 880ml. Make sense ?
This figure is probably lower for you and other good freedivers, say perhaps closer to %40 ?


Ulf, if my lung O2 stores were %50 of total, then with packing it would be %68.
8.4 vs 11.4 = %36 increase
P.S. I weigh 80kg, both my lung O2 stores and my blood would be much higher then Bill's example.

Cheers,
Wal

 

[Ulf]

No I think its 59% because the total O2 store increas as much as lung O2 when packing...
And yeah I figured that it wouldn't be corect.

Now look at the blood O2 store, when most people get down to say %50 SaO2 they would blackout. So the limit for the above example is 440ml blood O2 that can be used not 880ml. Make sense ?

That explains it. I think HV could have interesting effects on the amount of O2 from blood and/or lungs that can be used. The question is what...