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Increasing lung volume?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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New Member
Aug 19, 2002
I found a good deal on a spirometer on e-bay and can now accurately measure my VC. The problem is, it reaffirmed my fears of having small lungs. The very most I can get with packing is 5.5 liters. I believe it is accurate, because I tried some other, inexpensive methods of measuring my VC before I receiving the spirometer and the results were similar.

The good news, if there is any, is if you take into consideration the size of my lungs, my efficiency is right up there with world class.

So how much hope is there that I can expand my lung volume over time? Has anybody found that theirs increased over a few years of practice?
Problem is, you're measuring FVC, not TLC. You can exhale 5.5L. But, using your static times and comparing them to your lung volume doesn't necessarily mean you have high efficiency, maybe you actually have big lungs -- it depends on your residual volume.

So, your O2 storage depends on:
[ total lung capacity ] / [ body mass ]

Where TLC = FVC + residual volume

When I got my spirometer, I found that my numbers were getting higher and higher--but not because my lungs were getting any bigger--it was because I was getting better and better at exhaling more and more, i.e. reducing my residual volume.

So, if your residual volume is 3L, then your TLC is 8.5L. Another diver may have FVC of 7.0L, and RV=1.5L, for a TLC of 8.5L.

Remember that with the FRC system of diving, you only want to start the dive with 3 to 5L anyway. In so doing, you save dramatically on the descent, because there is little or no buoyancy to fight. Whenever people are worried about small lungs, I remind them that there is a style of diving which allows 80m+ dives, with nothing more than 4L lungs.

Eric Fattah
BC, Canada
Eric, or anybody,
How is residual volume measured? Thanks for the words of encouragement.
After six months of regular pack stretches the Vc measures almost 5% more. The amount that I can pack has been steadily increasing for two years. Please be careful talking about lung size. Some day I might believe that you need 7L and then I won't be able to do a decent static again.
After I posted I remember you had mentioned your lung size when you were describing how to estimate it with a balloon so I went back and looked up your post. I don’t feel so bad now.

I know what you mean about talking about lung size. Getting a spirometer was a two edge sword. :head
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