Use a balloon to estimate RV
So it’s been awhile since I estimated my residual lung volume (RV), and I figured it was time to do it again.
I’m a big guy, so my lungs hold a lot of air. When you’re blowing all your air into containers in the bathtub, and you’re ⅔ or more exhaled, is not the best time for pausing to move your straw to another container—or worse, refilling the container. This time I decided to use a balloon.
I took a deep breath, exhaled maxmially into the balloon, then blew the rest into the container through a straw. (Wait, did he just say “the rest” after “maximally exhaled”?) I heard that. Yes, you can’t exhale all of your air because the pressure in the balloon is higher than atmospheric pressure. In my case, I had another 400ml of air.
Then I emptied the air out of the balloon into the container. This is easy and leisurely once you figure out the trick, but it can seem next to impossible at first. Hint: don’t try to submerge the balloon. If you grab the lip of the balloon mouth only, and avoid pinching the neck, you can control the air flow very well. There, I had measured my vital lung capacity (VC).
It worked great, and compared with the last circus event when I measured VC it was much easier.
Now I had to figure out how to get from VC to RV. The clown who wrote http://hans.fugal.net/density kind of left this step vague. I’ve remedied that and added a page to my spreadsheet. For the curious, my RV is up from 2.0 liters to 2.2 liters, and a total lung capacity of 8.2 liters.