1. An Approach For Spirometry and DLCO Interpretation

2. PFT interpretations should be clear, concise and informative.
recording respiratory symptoms, such as cough, phlegm, wheezing and dyspnoea, as well as smoking status, and recent bronchodilator use could be helpful in this regard.

3. The interpretation will be most meaningful if the interpreter can address relevant clinical diagnoses, the chest radiograph appearance, the most recent haemoglobin value, and any suspicion of neuromuscular disease or upper airway obstruction (UAO).

4. Spirometry
Measurement of the air moving in and out of the lungs during various respiratory maneuvers. It allows one to determine how much air can be inhaled and exhaled , and how fast.

5. Spirometer and Lung Volumes/Capacities

6. Silhouette of Hutchinson Performing Spirometry
From Chest, 2002

7. Data generated Volume time curve (spirogram) Flow volume loop
FEV1, FVC, Ratio
Flow volume loop
Peak flow
FVC
FEF 25-75
Inspiratory flow data

8. Flow-Volume Loop
Illustrates maximum expiratory and inspiratory flow-volume curves
Useful to help characterize disease states (e.g. obstructive vs. restrictive)
Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003

9. Breathing

10. Breathing manoeuvres Forced spirometry with flow/volume-curve
From tidal breathing a slow and maximal exhalation has to be performed. After reaching the point of maximal exhalation (No.1) the patient inspires fast and maximal (No.1, 2, 3) on instruction.
Immediately after reaching maximal inspiration (No.3) the patient should blast out suddenly with maximal effort; time of exhalation 6 (4) seconds or there is no change in volume any more (No.3, 4, 5 right hand) 10

11. Pulmonary Factors Can Reduce Vital Capacity
Loss of Distensible Tissue
e.g. pneumonectomy, atelectasis.
Decreased Compliance.
e.g. respiratory distress syndrome, alveolar edema, or infiltrative interstitial lung diseases.
Increased Residual Volume.
e.g. emphysema, asthma, or lung cysts. 29

12. Extrapulmonary Factors Can Reduce Vital Capacity
Limited Thoracic Expansion.
e.g. thoracic deformities (Kyphoscoliosis) and pleural fibrosis.
Limited Diaphragmatic Descent.
e.g. ascites and pregnancy.
Nerve or Muscle Dysfunction.
Pain (surgery, rib fracture)
Primary neuromuscular disease (e.g. Guillain-Barré Syndrome). 30

13. The VC, FEV1, FEV1/VC ratio and TLC are the basic parameters used to properly interpret lung function.
FVC is often used in place of VC.
The FVC is usually reduced more than SVC in airflow Obstruction.