From what I saw when I met up with an old peds CF doc and he showed me my charts, best I blew was high 30%, 38% I think. I could go back till when I was about 8. It was usually around 33% and and as low as 25% when I got sick.
My lowest that I blew was 15%, about 8 months before my tx. I must have gone done to about 10% I think as I felt a lot worse after that.
Now with my new lungs I blow 42% on a bad day and without nebs and on a good day after nebs I blow 58%. I have emphysema now.