PFT Quick Reference

SYSTEMATIC EVALUATION OF PFTs
Jeanne M. Ferrante, M.D.

1. FEV1/FVC
>70%= normal
61-69%= mild obstruction
45-60%= moderate obstruction
< 45%= severe obstruction

2. FEF 25-75 (reflects small airways disease)
>79% predicted= normal
60-79% predicted= mild obstruction
40-59% predicted = moderate obstruction
<40% predicted = severe obstruction

3. FVC
80-120% predicted = normal
70-79% predicted = mild restriction
50-60% predicted = moderate restriction
<50% predicted = severe restriction

4. If FEV1/FVC <70% and FVC normal, repeat after bronchodilator:
a. If FEV1 or FVC increases by > 15% or FEF 25-75 increases by > 30% = asthma
b. No significant improvement = COPD

5. If FEV1/FVC is <70% and FVC <80%, check lung volumes.
a. TLC < 80% predicted = obstructive and restrictive disease
b. TLC normal with increased RV = air trapping, obstructive disease
c. TLC > 120% predicted = hyperinflation

To differentiate between different obstructive or restrictive diseases, check:
6. DLCO = diffusing capacity of lung for CO
measures ability of lung to transfer a gas from the alveoli to the capillary blood ( major
determinants are integrity of alveolar surface area, capillary bed, and Hb concentration)

a. Obstruction with hyperinflation and decreased DLCO = emphysema
Obstruction with hyperinflation and normal (or sometimes increased) DLCO = asthma
Obstruction with normal lung volumes and normal DLCO = chronic bronchitis

b. Restriction with low RV and decreased DLCO = scarring diseases (sarcoidosis,
diffuse interstitial fibrosis, berrylliosis, collagen vascular disease)
Restriction with normal RV (or increased) and normal DLCO = neuromuscular
diseases, kyphosis, scoliosis

c. Isolated low DLCO = anemia, pulmonary vascular disease (PE)