Interpretation of Pulmonary Function Test

Interpretation of Pulmonary Function Test

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

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

3. 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

4. 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

5. How Spirometry is performed?

6. FEV1

7. 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

8. 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

9. 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 ?

10. 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

11. 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