The Way You Breathe Can Make You Sick or Make You Well.
For awhile, I stopped using this after I noticed that some people, registered better breathing and did not breathe easier and some registered worse breathing and DID breathe easier. To me it is not always dependable. Later I learned to use it along with my other methods of measuring breathing. I get a more clear picture of progress this way. You will too. It can use to tell if you have the breathing volume of someone years younger than you.