A friend of mine said that he noticed a positive effect after his first session. The effect lasted a week. He tried again and it worked again. Anyway, he felt it did him so much good he bought one, and uses it once a week. It's the kind with no extra Oxygen.
He has offered to let some of use try out his machine. Nobody has reported the same effect he found. I had to shut if off right away because my ears hurt too much. If I were to try it again, I'd have to have chewing gum, just like I do when an airplane descends. One woman I know didn't try his, but when to the same place he first went. She got worse for months.
One thing my friend makes clear is he started feeling better in the last 10 minutes of his first 1 hour session. IOW, it is possible to know right away.