PFT Normals (FEV1 & FVC)

Normal >80%

Mild 70-79%

Moderate 55-69%

Severe <55%

per ATS a significant BDR is:

FEV1 change >/= 12% &

FEF25-75 change >/= 25%


PFT Normals (FEV1/FVC%)

Age <40:

Normal >75%

Age 40-60:

Normal >70%

Age >60:

Normal >65%

per ATS, airflow limitation (i.e. obstruction) is defined as abnormally low FEV1/FVC ratio for age (the absolute ratio, not the reported % of predicted).  A low FEV1 or FEF25-75 by themselves DO NOT constitue obstruction.  Once obstruction is confirmed by an abnormally low FEV1/FVC ratio, then the degree of obstruction (i.e. mild, moderate, severe) is determined by the FEV1 % of predicted value (see above).  To accuratelly diagnose restrictive ventilatory defects, formal measurement of TLC is needed.

PFT Normals (Diffusion)

Normal >75%

Mild 60-74%

Moderate 40-59%

Severe <40%


PFT Normals Max. expiratory force (MEF)

age 20-54 >55

men: 233+/-84 218+/-74

women: 152+/-54 140+/-40


PFT Normals Max. inspiratory force (MIF)

age 20-54 >55

men: 124+/-44 103+/-44

women: 87+/-32 73+/-26


PFT Normals (TLC)

Normal 80-120%

Mild 70-79 121-130%

Moderate 60-69 131-150%

Severe <60% >150%

PFT Normal Variations

    FEV1   FVC   FEF25-75
Within day            
Normal W5% W5% W13%
COPD W11% W13% W23%
Wk to wk      
Normal W11% W12% W21%
COPD W20% W20% W30%
Yr to yr W15% W15%  

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