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Pulmonary Function Tests Jonathan Kass

Pulmonary Function Tests Jonathan Kass

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Pulmonary Function Tests Jonathan Kass

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  1. Pulmonary Function TestsJonathan Kass Cooper University Hospital Robert Wood Johnson School of Medicine UMDNJ at Camden

  2. PFTs • Spirometry, Flow Volume Loop, MVV • Lung Volumes • Diffusing Capacity • Challenge Testing • Respiratory Muscle Testing • Airways Resistance

  3. What do PFTs Measure • How much air the lung can hold • How well the air moves through the airways • How well the oxygen penetrates the lung tissue in order to enter the blood stream • Respiratory muscle strength & endurance

  4. History of PFTs • 1718 Jurin: TV and FVC • 1800 Davy: gasometer TV,VC,RV • 1846 Hutchinson spirometer (height) • 1854 Wintrich spirometer (ht,wt,age) • 1868 Bert: body plethys in animals • 1959 Wright: peak flow meter • 1969 Dubois: body plethys in humans

  5. Davy Gasometer

  6. Hutchinson Spirometer

  7. Lung Volume Sub-Divisions

  8. Poor (Man’s) PFT

  9. Match Test • Extinguish a match from 6 inches away from the open mouth • Correlated with FEV1 >1.5L and MVV > 60 L/Min • Reverse less correlated (some with good function could not blow out the match) • Dines DE. Minn Med 1968; 51:33-36

  10. Spirometers • Pneumotachygraphs: Flow signal is integrated to obtain volume & is calibrated for air only • Rolling-seal • Water-seal: inaccurate with high flows or MVV

  11. Rolling Seal Spirometer

  12. Spirometric Maneuvers • Maximum expiration made as rapidly as possible after a maximum inspiration (Forced Vital Capacity) • Maximum expiration made slowly after a maximum inspiration (Slow VC)

  13. Spirometric Measurements

  14. Volume Time Curve

  15. Forced Vital Capacity • Maximum volume of air which can be exhaled or inspired during a forced maneuver (at least 6-12 seconds) • Most effort independent PFT w/ least variabilty

  16. Etiologies of a Decreased Forced Vital Capacity • Obstruction • Restriction • Sub-optimal effort

  17. Slow Vital Capacity (SVC)

  18. Slow Vital Capacity • SVC is always > FVC • The greater the airways obstruction the greater the difference btw FVC & SVC

  19. Peak Expiratory Flow Rate • Assesses maximal effort • Effort dependent • Strength of expiratory muscles • Large airways (trachea & main bronchi)

  20. FEV1 • Less effort dependence than Peak Flow • Assessment of degree of airway obstruction when present • Assessment of bronchodilator response

  21. FEV1/FVC • When decreased best indicator of airway obstruction • When normal does not exclude airway obstruction if values are decreased in parallel

  22. FEF25-75% • Small airways obstruction • Effort Independent • Dependent on FVC and high variability limiting its clinical utility • Epidemiological studies

  23. Maximum Spirometic Values • Maximum values of 3 technically satisfactory tests provided the 2nd best test is within 100ml or 5% • Best FVC and FEV1 can be from separate maneuvers • Alternative: Mean of 3 best tests

  24. Assessment of Presence of Airway Obstruction • Low FEV1/FVC • Flow volume loop • Evidence for air trapping from SVC-FVC difference, bronchodilator improvement, or from increased RV/TLC (especially in children)

  25. FEV1/FVC Ratio • Inversely related to age and height • Can be decreased in athletes, deep sea divers, miners, tall people

  26. Variables Affecting Spirometry Becklake MR. Am J Med 1986:80:1158-63

  27. Assessment of Severity of Airway Obstruction Based on % Predicted FEV1 if the FEV1/FVC is Below the Normal Range • Mild: 70-100% • Moderate: 60-70% • Moderate to Severe: 50-60% • Severe: 34-50% • Very Severe: < 34% • ATS: ARRD 1991; 144: 1202-1218:

  28. Assessment of Bronchodilator Response • Increase in FEV1 of 12% & 200cc • Increase in FVC of 12% & 200cc but ? due to improved effort or decreased air trapping (ATS: ARRD 1991; 144: 1202-1218) • > 15% increase (ACCP Chest 1974; 65: 552-553)

  29. Flow Volume Loops

  30. Flow Volume Loops

  31. Flow Volume Loops

  32. Flow Volume Loops

  33. Maximum Voluntary Ventilation (MVV) • The volume of gas that can be breathed in 12-15 seconds extrapolated to 1 minute. • Usually 35-40 X the FEV1 • Optimal MVV with RR 120/min and TV 30% of VC (Resp Physiol 1968; 5: 118-129)

  34. Maximum Voluntary Ventilation (MVV) • Indicator of respiratory muscle strength and endurance • Weaning and Pre-op assessment • Decreased in obstruction in proportion to the FEV1 • Not usually decreased in ILD

  35. Maximum Sustained Ventilation(MSV) • 100% of MVV < 1 minute • 5% of MVV indefinitely • Energy supply to respiratory muscles adequate to sustain ventilation at about 55% of MVV in normals (Resp Physiol 1968; 5: 187-201)

  36. Conditions associated with MVV/FEV1 < 30 • Poor Effort • Neuromuscular, musculoskeletal, fibrothorax, abdominal distention • Fixed and variable extrathoracic airway obstruction (< 20) • Owens GR. Spirometric diagnosis of UAO. Arch Int Med 198; 143:1331-34

  37. Conditions associated with MVV/FEV1 > 50 • Interstitial Lung Disease • Supra-effort

  38. Spirometry Interpretation

  39. Spirometry Interpretation

  40. Indications/Ordering of PFTs • ASTHMA: Methacholine Challenge • COPD/ABNL X-RAY: Full PFT • DYSPNEA: Full PFT with Methacholine challenge • PRE-OP: Spirometry w/ MVV • DRUG EFFECT: Spirometry and DLCO

  41. Equine PFTs

  42. PFT Quiz • 3 causes of a decreased FVC? • What is the best PFT indicator of airway obstruction? • What is the most reproducible PFT measurement? • What is the best PFT test to see UAO?