Once the testing is complete, look at the data obtained and ask yourself a succession of questions.
1) Is it a good test, that is, are you satisfied that the subject put forth the best effort possible?
To determine this, look at the data: Do you have two sets of data that are close in value; do the flow/volume loops overlap? Also, look at the PEFR.
What Data Tells You (con't)
2) Are all the values within normal limits (80% - 120% of what was predicted for the subject)?
3) If the values are not all within normal limits, is the abnormality more indicative of a restrictive disorder or an obstructive disorder (or possibly both)? If the FEV1, FEV1/FVC, and/or FEF25%-75% is low, the abnormality is most likely obstructive. If the flows are normal but the FVC is low, the abnormality is most likely restrictive (however, this needs to be confirmed by measuring the TLC in a PFT lab).