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How do I measure lung capacity?

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Gyre

Member
Jul 4, 2016
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Simplest system I have seen to measure vital capacity (exhalable air) was an airtight flagon of water with two hoses leading into the top and glued in place, with the tips of the hoses on the bottom of the container. Exhaling into one displaced the water out of the other into a measuring bowl. But in the end lung capacity is not that important.
 

Mike H

Member
Jun 12, 2016
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Quick google got me the following child experiment. But I think it works fine. Though I wouldnt make all those lines.
 

Bill

Baron of Breathold
Oct 17, 2001
1,805
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It may be more useful to measure total volume. Many variables to work with of course (water density, weight of lead in water and consistency of lung fill). With no suit and a few kilos of lead, pull down until neutrally buoyant. Compare that to the amount of lead you can float on the surface with. Volume of gas is inversely proportionate to pressure in atmospheres.
 

J Campbell

Well-Known Member
Sep 17, 2001
595
179
148
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hmmm Bill, can you explainthat in more detail? You said compare WEIGHTS on surface and at neutral buoyant - but then didn't use the weight at all in the next sentence (volumme vs pressure)
 

Bill

Baron of Breathold
Oct 17, 2001
1,805
332
188
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The easy way to get total lung volume approximately is if you can get your body density. I use cheap plastic calibers and have used the in the water weighing. My number is 1.06. This means that if my lungs were empty, at 75 kilos my body would weigh 4.5 kilos if it was submerged in fresh water. Lead submerged in fresh water weighs 90% as in air. My weight for dynamic is 4.4 kilos (4 kilos submerged) and I'm slightly buoyant on the surface (neutral at one meter). 4k for lead and 4.5k for body comes to leads to a rough 8.5 liters in the lungs. That is the same as the tech at the hospital measured with his million dollar machine. I checked at depth and I'm neutral at 17-18 meters. Water density just under 1.03. Sounds close.
 
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