Pulmonary Function Testing

1. Pulmonary Function Testing Sandra B. Weibel MD Thomas Jefferson University

2. Indications • Differential diagnosis of dyspnea • Provides objective assessment of symptoms versus severity • Determine fitness for surgery • To guide therapy • To follow the course of a disease

4. Physiologic classification of disease • Obstructive Impairment- Airway limitation due to the resistive properties of the respiratory system • Restrictive Impairment- Loss of volume capacity of the lung due to loss of air space units or inability to expand the respiratory system

5. Obstructive Processes • L ocal obstruction • A sthma • C hronic bronchitis (COPD) • E mphysema

6. Restrictive Processes • P leural disease • A lveolar filling processes • I nterstial lung disease • N euromuscular diseases • T horacic cage abnormailites

7. Spirometry • Most widely performed study and is important in initial screening of patients • Easily and quickly performed in many settings

8. Types of spirometers • Types include flow (pneumotach) or volume (water seal, rolling and diaphragm) • Water seal device previoisly most commonly used in pulmonary function labs of the volume • Collect exhaled gas and act as a reservoir for inhaled gas • Composed of a mouthpiece, bell system and a pen on a rotating drum

11. Volume Displacement Spirometer

12. Flow Spirometry

13. Calibration of spirometer • Warmed up and temperature controlled Barometric pressure and temperature recorded • Volume calibration with 3L syringe (within 3%) • Flow spirometer tested at 3 flow rates between 2 and 12L

14. Quality Control

16. Prior to testing

17. Performing the maneuver • It is a forced expiratory maneuver and the patient must be sitting upright in a chair with lips around a mouthpiece • After a maximal inspiration, a forced and rapid expiration is made • Quality of the maneuver needs to be assessed noting that the patient started at zero, had a maximal initial efffort and lasted 6 seconds.

20. Measurements • FVC • FEV1 • FEV1/FVC • Also FEF25-75 and TET

21. FVC Measurement

22. FEV1 Measurement

23. Flow volume

24. Interpretation • First need to assess the quality of the maneuvers • Choice of reference values • Use of LLN • Compare to previous tests • Race adjustments

25. Restrictive Lung FVC AND FEV1 decreased FEV1/FVC normal FEV1 main distinguishing feature Obstruction FEV1 decreased FVC Normal FEV1/FVC are low Interpretation

26. Pitfalls in Interpretation • Predicted need to fit your population • Non Caucasians have lower lung volumes and this may need to be addressed • Prior to interpretation the test needs to be assessed to see if it meets standards • Machines need to be calibrated daily to ensure accuracy

27. Effort

29. Poor effort

32. Interpretation • The patient’s data is compared to predicted • Predicted values are obtained after studying populations of normal nonsmokers and then regression equations developed • Regressions are based on sex, height, and age.

33. Predicted Values

34. Decline in PFTS

35. References • Many different ones used in past Knudson Crapo etc • Current recommendation is NHANES III • This studied over 7000 individuals • Included Caucasians, blacks and Mexican Americans

40. Interpretaion • Normal is > 80% of predicted • Mild impairment 65-79% • Moderate 50 -64% • Severe < 50%

41. Interpretations

42. Flow Volume Loops • Inspiratory loops can also be obtained to evaluate for the presence of large airway obstruction • Theory changes in pressure outside and inside the thoracic cage will cause changes in airway diameter • These airway changes can cause a limitation to airflow if large enough

43. Extrathoracic Obstruction

44. Intrathoracic Obstruction

45. Fixed Obstruction

46. Large Airway Obstruction

48. Bronchodilator Response

49. Bronchodilator testing • No short acting agents for 4 hrs • No long acting beta agonists for 12 hrs • No theo for 12 hrs • No smoking for 1 hr • Beta agonist given recommended 4 puffs and wait 10-15 minutes later