PFT Interpreter
Enter the core values from the PFT report to identify the ventilatory pattern, air trapping, and diffusing capacity abnormality.
Spirometry
FEV1
Used primarily to describe severity of airflow limitation
%
FVC
Reduced FVC may reflect restriction or air trapping
%
FEV1/FVC
Primary measurement used to identify obstruction
FEV1/FVC LLN
Lower limit of normal from the PFT report
Lung Volumes
TLC
Reduced TLC confirms restriction
%
RV/TLC
Elevated values support air trapping
%
Diffusing Capacity
DLCO
Helps distinguish parenchymal, vascular, and emphysematous processes
%
Advanced DLCO
VA
Optional alveolar volume
%
KCO / DLCO-VA
Optional transfer coefficient
%
Bronchodilator Response
FEV1 change
Post-BD increase as % of predicted FEV1
%
FVC change
Post-BD increase as % of predicted FVC
%
Quick interpretation guide
- Obstruction: FEV1/FVC below the lower limit of normal.
- Restriction: reduced TLC.
- Mixed defect: reduced FEV1/FVC and reduced TLC.
- Possible restriction: reduced FVC with preserved FEV1/FVC when TLC is unavailable.
- Nonspecific pattern: reduced FEV1 or FVC with preserved FEV1/FVC and normal TLC.
- Air trapping: elevated RV/TLC, particularly with a normal or elevated TLC.
DLCO patterns
- Low DLCO + obstruction: consider emphysema, pulmonary vascular disease, or combined parenchymal disease.
- Low DLCO + restriction: supports parenchymal lung disease.
- Low DLCO with otherwise normal PFTs: consider pulmonary vascular disease, early ILD, early emphysema, or anemia if the DLCO was not hemoglobin corrected.
- Normal or high DLCO + obstruction: asthma or chronic bronchitis is more likely than emphysema.
Flow-volume loop patterns
- Inspiratory flattening suggests variable extrathoracic obstruction.
- Expiratory flattening suggests variable intrathoracic obstruction.
- Flattening of both limbs suggests fixed central airway obstruction.
- Expiratory scooping supports obstructive physiology.