Even though I obsess over any miniscule change in PFTs, my doctor
doesn't unless there's like a 10% difference (which there never is
thankfully). A good part of PFTs comes down to technique, whether
you're tired, whether you've had a good cough before hand and so
on. In fact, my PFTs differ depending on what part of the day it
is, I never have my appointments in the morning, I am not a morning
person, I cough all morning, feel tired and have these little
bronchospasms, all which affect my PFTs, so I make sure my
appointments are in the afternoon because that's when I feel
better. <br>
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Also, like the other posts said, it's not the sole predictor of how
one's health is. There have been many times where I have been quite
sick and PFTs still look good on paper. There are many others on
this site that have lower PFTs to me and run, work full time etc so
it's only one piece of the puzzle.