I bought one on the "push" from a friend and NEVER use it. I do deep breathing exercises... Deep long breathing in thru nose and long deep breathing out thru month to keep lungs healthy. I learned the breathing work from an occupational therapist when I was in rehab situation with damaged knee issue.

I bought it long before the CV.

I also believe due to quality antioxidants I've been taking for years, lungs are in good shape.