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Pulmonary Function Testing

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  • 1. Pulmonary Function Testing Frank Sciurba, M.D.
  • 2. Indications for Pulmonary Function Testing 1. Categorization of the type and severity of physiologic perturbation • Restrictive vs. obstructive categorization – Asthma vs. emphysema 2. The objective assessment of pulmonary symptoms. – Documentation of abnormality – Disability assessment 3. Documentation of progression of disease. – COPD – Neuromuscular disease such as ALS
  • 3. Indications for Pulmonary Function Testing 4.Documentation of the patient’s response to therapy. • Asthma control • Lung volume reduction surgery 5.Preoperative assessment • Lung cancer resection • Timing of lung transplantation 6.Screening for sub clinical disease • Emphysema in a tobacco smoker. • Occupational risk.
  • 4. Component of respiration Pulmonary function test Ventilation a. Spirometry (FVC, FEV1 etc.) b. Lung volume (RV, FRC, TLC) – Plethysmography – Helium dilution a. Inspiratory and expiratory pressure (MIP, MEP) b. Lung compliance (rarely actually measured clinically) c. Maximal voluntary ventilation (MVV) d. Exercise ventilation (Ve-max, Vd/Vt) Diffusion Diffusing capacity Exercise Oxygen Saturation Circulation Diffusing capacity (DlCO) Cardiopulmonary exercise testing (VO2 - max) Control (see Sanders lecture)
  • 5. Spirometry • Measures how much and how fast • Most common and simple test (can be performed in primary care office)
  • 6. Spirometry • Only measures what comes out • How much and how fast? • How much: Vital Capacity – A strong prognostic indicator in Framingham study for all cause mortality • Slow vital capacity (SVC) vs Forced Vital Capacity (FVC)
  • 7. Measurement of Forced Vital Capacity (FVC) 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 Seconds Liters (BTPS ) FVC = 5.8 L
  • 8. Spirometry: How Fast? • Forced expiratory volume in one second (FEV1) – Reduced with both small lungs (restriction) and with diseases causing resistance to airflow (obstruction) • FEV1/FVC ratio – Value < 0.70 defines obstruction • FEF 25-75 – Only important when FVC and FEV1 are normal – Sensitive to earlier disease “minimal obstruction”
  • 9. 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 Seconds Liters (BTPS ) FEV1 = 4 L Measurement of Forced Expiratory Volume (FEV1 )
  • 10. 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 Seconds Liters (BTPS ) Spirometric Changes with Increasing Degrees of Obstruction
  • 11. Hyperinflation in Emphysema
  • 12. Spirometry-Quality Control • Technician dependent • Acceptable effort – sharp peak – gradual return to 0 flow – At least 4 seconds • 3 acceptable maneuvers within 5% of each other • Often more easily seen on Flow-volume tracings
  • 13. Normal/Predicted Values • Height • Age • Gender • Race – 10% lower in Asian and African than European descent
  • 14. Predicted Normal Examples • 21yo 6’6” male- FVC predicted- 6.9 L – Therefore a measured value of 2.1 L would be only 30% predicted. • 80yo 4’10” female- FVC predicted- 1.9 L – Therefore a measured value of 2.1 L would be 111% predicted Which individual would be most likely to tolerate lung resection?
  • 15. Spirometry and Detection of Disease Normal Values • FVC ≥ 80% of predicted • FEV1 ≥ 80% predicted • FEV1/FVC ratio ≥ 0.70 • FEF 25-75 ≥ 65% predicted – Greater variance in the measurement
  • 16. Obstruction vs. Restriction
  • 17. Obstructive Lung Disease • FEV1/FVC < 0.70 defines obstruction • FEV1 usually decreased • FVC may be decreased – e.g. if expiration incomplete due to air trapping • If FEF 25-75 decreased and all of the above are normal – “Minimal airways obstruction”
  • 18. Restrictive Lung Disease • FVC Decreased • FEV1 often decreased proportionate to FVC • FEV1/FVC Normal or Increased • Can have simultaneous obstruction and restriction • May need lung volume measurements (RV, FRC, TLC) to confirm.
  • 19. • Patient retested before and after administration of a beta agonist bronchodilator • Determines reversibility (asthma) • 15% and 200ml improvement indicates a positive bronchodilator response Bronchodilator Response
  • 20. Bronchial Challenge Testing • Pulmonary function in the laboratory may not represent the function at the time of symptoms. • Attempt to mimic condition of symptoms – Work place chemicals – Cold air – Exercise • Methacholine (histamine derivative) induces bronchospasm in occult asthmatics • 20% decrease indicates a positive challenge test
  • 21. Peak Expiratory Flow (PEF) • Can be obtained during spirometry • Portable devices can be used to make meaurements at home or in work place
  • 22. Flow-Volume loops •same data as volume-time plots but separate graphical representations allow the human eye to recognize patterns.
  • 23. Normal Obstructed
  • 24. F-V loops • The assessment of patient effort on repetitive testing • The presence of specific patterns for upper airway obstruction • Specific patterns in other disease processes confirm but add little to spirometry numbers
  • 25. F-V loops in Upper Airway Obstruction • Intra vs. Extra-thoracic • Variable vs. Fixed
  • 26. Variable Extrathoracic Upper Airway Obstruction •“inspiratory plateau” •e.g. glottic tumor
  • 27. Variable Extrathoracic Upper Airway Obstruction
  • 28. Intrathoracic Variable Upper Airway Obstruction •“expiratory plateau” •e.g. tracheal tumor
  • 29. Intrathoracic Variable Upper Airway Obstruction
  • 30. Fixed Upper Airway Obstruction
  • 31. Measurement of lung volume
  • 32. 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 Seconds Liters (BTPS ) Spirometric Changes with Increasing Degrees of Obstruction
  • 33. Hyperinflation in Emphysema
  • 34. Severe Emphysema (decreased FVC but increased FRC & RV)
  • 35. Measurement of lung volume • Helium dilution • Body plethysmography
  • 36. Helium Dilution Lung Volume Measurement
  • 37. Body Plethysmography
  • 38. B o x P r e s s u r e Mouth Pressure Plethysmographic Determination of FRCPlethysmographic Determination of FRC
  • 39. Body Plethysmography- Technique
  • 40. Plethysmography vs. Helium technique • Plethysmography equipment more expensive and requires more technical expertise • Helium falsely low in bullous emphysema – Plethysmography measures all air in the chest including non-communicating bullae; Helium only measures alveoli communicating with the mouth
  • 41. Measurement of Diffusing Capacity
  • 42. Diffusing Capacity • Gas exchange (not ventilation) • Clinically assesses pulmonary capillary bed in contact with ventilated alveoli • Influenced by – Capillary volume – Capillary surface area • Single breath Carbon Monoxide (CO) technique now most common.
  • 43. Single breath Carbon Monoxide Diffusing Capacity (DlCO) • Simple/automated • Standardized normal values available • 10 second breath hold • Inspire mixture of CO, He and O2 • Measure change in volume of CO between inspiration and expiration adjusted for dilution effect with He
  • 44. Single breath Carbon Monoxide Diffusing Capacity (DlCO) Technique
  • 45. Conditions Lowering Diffusing Capacity 1. Loss of alveolarcapillary membrane • emphysema • pulmonary fibrosis • pulmonary vascular disease 2. alveolar filling diseases • congestive heart failure • pulmonary alveolar proteinosis 3. decreased total lung volume • neuromuscular disease • chest wall deformities • patient post pneumonectomy
  • 46. Conditions Increasing Diffusing Capacity • Polycythemia • Mild congestive heart failure • Asthma • Pulmonary hemorrhage.
  • 47. Thank You