Its a very simple and effective measuring procedure. The test can be performed in two ways, as one deep breath or a series of breaths over a few minutes. First, you will be asked to breathe through a machine that supplies you with nothing but pure oxygen. No other gases will be present in the air. Then, you will exhale as long as possible through the machine that will then read the amount of nitrogen in your breath. Since nitrogen is not exchanged in the lungs, it sits there until you exhale. But if your breath is too shallow due to respiratory inflammation, it does not escape easily.

Nitrogen washout (or Fowler's method) is a test for measuring anatomic dead space in the lung during a respiratory cycle, as well as some parameters related to the closure of airways.
The helium dilution technique is the way of measuring the functional residual capacity of the lungs (the volume left in the lungs after normal expiration). This technique is a closed-circuit system where a spirometer is filled with a mixture of helium (He) and oxygen.

I can think of hundreds of questions until I'm sitting in front of my doctor. Then I get dumb as dirt. Wrote some down one day and left them on the coffee table. Word of advice. Don't GOOGLE your symptoms. I was a wreck doing that. Lol Good luck!

Dear Sharona . Helium is much lighter than air. It is therefore often used as a filler for balloons and airships. did you have in mind for inhalation? Here in the Netherlands there is wintry snow. also not good for the airways. the summer is wonderfully warm and good. kind regards Rene

Im gonna start using my memo pap on my phone. I am shy believe it or not. Lol especially with doctors