Interpretation of Pulmonary Function Test

1. A Stepwise Approach to the
Interpretation of Pulmonary
Function Tests
Dr Suman Roy
PGT

6. Why PFTs?
• Dx of Symtomatic Ds
• Screening of Early Asymtomatic Ds
• Prognostication of Known Ds
• Monitoring Response to Known Ds

7. Purpose of PFTs ?
As a dx tool it helps to classify LD into 1 of 3 broad categories
Obstructive Lung Disease Restrictive Lung Disease PulmonaryVascular Disease
COPD
(Chr. Bronchitis< ->Emphysema)
Asthma
Bronchitis
Cystic Fibrosis
ILD
( Pul Fibrosis, Sarcoidosis)
Chest Wall Pathology
( Kyphosis, Scoliosis)
Obesity
Neuromascular Disease
( ALS, Mascular Dystrophy)
Pr Pul HTN
Chr Thromboembolic Ds
These categories are not mutually exclusive :
COPD can be Obstructive + Vascular
Sarcoidosis can be Restrictive + Obstructive + Vascular

8. Function of Pulmonary System Tested by PFTs
• Airways
Large & Small Airways
• Parenchyma
Alveoli
Interstitium
• Pulmonary Vasculature
• Bellows/Pump Mechanism
Diaphragm
Chest Wall
• Neural Control of Ventilation

14. How Spirometry is performed?

16. FEV1

20. Values Measured by Spirometry
Major Minor
FEV1
FVC
FEV1/FVC
Flow Volume Loop
Peek Expiratory Flow Rate
(PEFR)
PEF (25-75)
Maximum Voluntary Ventilation
Response to Bronchdilators

21. Interpretation of FEV1, FVC
& FEV1/FVC Ratio
FEV1 FVC FEV1 / FVC Ratio
( Tiffeneau Index)
Obstructive Lung
Disease
Normal
Very mild obstruction
or Decreased
Mod / Severe
Obstruction
Normal
Mild / Moderate
obstruction
Decreased
Severe obstruction
Decreased
< 70%
Restrictive Lung
Disease
Normal
or Decreased
Decreased Normal
or Increased
70 % or More

22. Interpretation of Spirometry
Assess Low Assess Normal/High Assess
FVC FEV1/FVC FVC
LOW Normal Low Normal
Obstruction Obstruction Possible Normal Lung
Or Mixed Restriction Mechanics
Where is Pulmonary Vascular Disease ?

40. Staging of COPD Based on FEV1
The Global initiative for Chronic Obstructive Lung Disease
(GOLD) classifies COPD severity based on post-bronchodilator FEV1
FEV1 compared to predicted for Age/gender/height
GOLD Stage I FEV1 _> 80%
GOLD Stage I I 50% _< FEV1 _< 80%
GOLD Stage I I I 30% _< FEV1 _> 50%
GOLD Stage I V FEV1 _< 30%
FEV1/FVC < 0.7 There is weak co-relation between FEV1 & Quality of Life

41. GOLD Criteria for Severity of Airflow Obstruction in COPD
GOLD Stage Severity Spirometry
• I Mild FEV1/FVC <0.7
FEV1 ≥80% predicted
• II Moderate FEV1/FVC <0.7
FEV1 ≥50% but <80% predicted
• III Severe FEV1/FVC <0.7
FEV1 ≥30% but <50% predicted
• IV Very severe FEV1/FVC <0.7
FEV1 <30% predicted