Pulmonary Function Testing

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Review of Pulmonary Function Testing
Edward Omron MD, MPH, FCCP
Pulmonary Medicine
Morgan Hill, CA 95037

Published in: Health & Medicine
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Pulmonary Function Testing

  1. 1. TI ON N C FU Y CP AR N H ,F C O M P LM ING M D, ESPU ST R ON VIC TE R D O M SER RY W A O NA ED LM PU
  2. 2. LEXICON OF PULMONARY FUNCTION TESTS (PFT’S)Spirometry (measurement of flow) Bronchodilator response Bronchoprovocation (methacholine, histamine, exercise)Measurement of lung volumes Plethysmography Gas dilutionGas exchange DLCO Arterial blood gas analysis
  3. 3. LEXICON OF PULMONARY FUNCTION TESTS (PFT’S)Respiratory muscle strength Pi-max; Pe-max; MVV; OthersCardiopulmonary exercise testing (CPET) Determines area of performance limitationExhaled monoxides Nitrous oxide; Carbon monoxide
  4. 4. INDICATIONS FOR PFT’S Work compensation &Dyspnea disabilityPre-op evaluation Surveillance of General occupational Pre-lung resection lung dxAbnormal radiograph Aid in dx of lungFollow pulmonary disease disease & therapy Rotating throughFitness for pulmonary employment, recreation
  5. 5. PHYSIOLOGY AND PATHOPHYSIOLOGY Chest Skeleton, and Muscles of Inspiration and Expiration. Elastic Force of chest is to EXPAND OUTWARD
  6. 6. PHYSIOLOGY AND PATHOPHYSIOLOGY Movement of chest in breathing. Mobility of thoracic cage is reduced with age, neuromuscular disease, arthritis, kyphoscoliosis, others.
  7. 7. PHYSIOLOGY AND PATHOPHYSIOLOGY Green bands represent ELASTIN Tendency of normal lung is to CONTRACT INWARD (COLLAPSE) DECREASED ELASTICITY – RELATIVE INCREASE IN VOLUME INCREASED ELASTICITY – RELATIVE DECREASE IN VOLUME
  8. 8. PHYSIOLOGY AND PATHOPHYSIOLOGYDETERMINATION OF VOLUME Balance between OUTWARD ELASTIC FORCE OF CHEST and INWARD ELASTIC FORCE OF LUNGS that DETERMINES LUNG VOLUME Held together by intact pleural space
  9. 9. PHYSIOLOGY AND PATHOPHYSIOLOGYDETERMINATION OF VOLUME Balance of forces at various lung volumes. FUNCTIONAL RESIDUAL CAPACITY is point where no muscle force is added; resultant lung volume is balance of elastic forces of chest wall and lung ZEN POINT
  10. 10. PHYSIOLOGY AND PATHOPHYSIOLOGY CAUSES OF RESTRICTIONIncreased lung elasticity Interstitial fibrosis, pneumonitis,edema, pneumoniaAirspace filling processes Edema, pneumonia, blood, protein, tumor, BOOPPleural disease and pleural space filling Effusions, pleural fibrosis, tumors, inflammatory rindsDecreased Chest wall elasticity/compliance Edema, burns, tumors, kyphoscoliosis, prolonged immobility, severe obesity, arthritis.
  11. 11. PHYSIOLOGY AND PATHOPHYSIOLOGY CAUSES OF RESTRICTION – CONT.Neuromuscular diseases Paralysis, ALS, Guillian Barre, MS, spinal disease, SLE shrinking lung syndrome, polymyositis, etc. Posts general anesthesia, especially abdominal surgeryAirspace removing (lung resection).Pulmonary vascular Chronic thromboembolic disease
  12. 12. PHYSIOLOGY AND PATHOPHYSIOLOGYREDUCED VOLUME = RESTRICTION
  13. 13. PHYSIOLOGY AND PATHOPHYSIOLOGY AIRWAY PHYSIOLOGYBronchi are tethered by elastin in interstium. Higherlung volumes and increased elastic recoil will increasediameter of airways. Decreased elastin will allowairways to flop closed.
  14. 14. PHYSIOLOGY AND PATHOPHYSIOLOGY AIRWAY PHYSIOLOGY Flow rate higher at higher lungAirway resistance is volumes and with increasinginversely effort. At low lung volumesproportional to lung flow rate doesn’t change withvolume increased effort
  15. 15. PHYSIOLOGY AND PATHOPHYSIOLOGYAIRWAY PHYSIOLOGY Curve A is maximal effort: Curve B is initially slow than forced Curve C is sub maximal effort throughout. Note that towards Residual Volume, flow cannot be increased with increasing effort
  16. 16. PHYSIOLOGY AND PATHOPHYSIOLOGY AIRWAY PHYSIOLOGYCONCEPT OF EQUAL PRESSURE POINT: Point of airway collapse byresulting pleural pressure. As lung volume is reduced on exhalation,EPP moves toward periphery, so lung cannot collapse withexhalation. Increasing pleural pressure (effort) does not change pointfor given volume. Cartilaginous rings in proximal airways preventcollapse at high lung volumes. Tracheomalacia results in earlyobstruction to flow.
  17. 17. PHYSIOLOGY AND PATHOPHYSIOLOGY AIRWAY PHYSIOLOGYEqual Pressure Point Pleural Pressure Gradientmaintains lung volume even with gravity accounts forat residual volume (RV) difference in ventilation and(CXR on right) alveolar volume
  18. 18. PHYSIOLOGY AND PATHOPHYSIOLOGY OBSTRUCTION AND HYPERINFLATION Early distal airway closure at highIn emphysema, loss of elastic lung volume. PEEP maneuver torecoil & loss of airway tethering increase airway pressure
  19. 19. PHYSIOLOGY AND PATHOPHYSIOLOGYOBSTRUCTION AND HYPERINFLATIONREASONS FOR HYPERINFLATION: 1) Loss of lung elastic forceinward shifts equalibrium to higher volume. 2) Early distal airwayclosure causes air trapping. 3) Patients attempt breathing athigher lung volume to maintain airway patency. Chest becomesfixed (barrel chest).
  20. 20. PHYSIOLOGY AND PATHOPHYSIOLOGY OBSTRUCTION AND HYPERINFLATION Obstruction and air trapping Mechanisms of obstruction ASTHMAEmphysema and Bronchitis:
  21. 21. DISEASES OF OBSTRUCTIONCOPD Asthma, Emphysema, Chronic bronchitis, mixedAcute bronchitisBronchiolitis obliteransBronchocentric granulomatosis
  22. 22. DISEASES TYPICALLY WITH MIXEDOBSTRUCTION AND RESTRICTIONSarcoidosisLymphangiomyomatosisLangerhans Cell GranulomatosisCHFPneumoniaLung removal with obstruction in remaining lung.
  23. 23. PULMONARY FUNCTION TESTING VOLUMES AND CAPACITIESCapacities aremade up of twoor more Volumes Note that Residual Volume, and hence any Capacity including it, cannot be measured by spirometry alone.
  24. 24. PULMONARY FUNCTION TESTING VOLUMES AND CAPACITIESTotal LungCapacity(TLC),FunctionalResidualCapacity(FRC), &ResidualVolume (RV)For normaland diseasestates.
  25. 25. PULMONARY FUNCTION TESTING SPIROMETRYForced Vital Capacity Maneuver: Seated patient. Blows outforcefully from TLC and carries out for > 6 seconds. Spirometermeasures FLOW VOLUME and FLOW RATE
  26. 26. PULMONARY FUNCTION TESTING SPIROMETRYNormal Volume-Time curve above;note leveling. ATS requirement is tocarry out for minimum six seconds.Normal Flow-Volume to right; noterapid rise, convex curve down,round inspiratory limb.
  27. 27. PULMONARY FUNCTION TESTING SPIROMETRYFev1; litres & % predicted.FVC; litres & % predicted.Fev1/FVC >> ABSOLUTERATIO OF VOLUMES (not% predicted)Fev1/FVC nl ~.80(.70-.90)Reduced Fev1/FVC is sinequa non of obstruction
  28. 28. PULMONARY FUNCTION TESTS PREDICTED VALUESStudies of large number of normals in a population – Caucasian, African, AsianBell shaped curveVariables taken into account Race, height, age, gender --Not weight“Normal” generally considered (80-120%)Applies to Spirometry, Volumes, DLCO
  29. 29. PULMONARY FUNCTION TESTSPREDICTED VALUES CONT.Problems: Not all populations represented precisely – eg, Filipinos are classified as “Asian” Some normals can fit out of bell curve
  30. 30. FORCED VITAL CAPACITY MANEUVERArtificial maneuverStandard means of measuring functionVery reproducible with coaching and observationLearning phenomenon occursPoor cooperation or malingering can be detected by comparison of flow volume loops
  31. 31. FEV1 AND FEV1/FVCFev1 single most important value in following and prognosticating COPD and preoperative evaluation for lung resectionFev1/FVC Down in obstruction May be supranormal, normal, or down in restriction, depending on pathology.  Pure interstitial fibrosis- up  Mixed restriction / obstruction – normal  Lung removal with existing lung obstructed – down
  32. 32. SPIROMETRY PATTERNS IN FLOW & FLOW VOLUMEMild obstruction Mod obstruction Severe obstruction
  33. 33. SPIROMETRY ObstructionPATTERNS IN FLOW & FLOW VOLUME
  34. 34. SPIROMETRY Obstruction PATTERNS IN FLOW & FLOW VOLUMEFVC vs. Slow VC In severe obstruction FVC can be reduced despite hyperinflation because of early airway closure Comparison with Slow VC (unforced, un-timed maneuver) can show large difference
  35. 35. SPIROMETRYPATTERNS IN FLOW & FLOW VOLUME Fixed Obstruction Variable Variable Extrathoracic Intrathoracic Obstruction: Obstruction
  36. 36. SPIROMETRY PATTERNS IN FLOW & FLOW VOLUME Typical Spirometry: FVC = 65% predicted Fev1 = 65% predicted Fev1/FVC = .90Mild to SevereModerate RestrictionRestriction
  37. 37. SPIROMETRY OBSTRUCTIONPATTERNS IN FLOW & FLOW VOLUMEFev1 90% Fev1 30%FVC 110% FVC 66%Fev1/FVC .65 Fev1/FVC .45Fev1 65%FVC 82%Fev1/FVC .52
  38. 38. SPIROMETRY BRONCHODILATOR RESPONSEAlbuterol by MDI/spacer given after baseline spirometry reveals obstruction.ATS criteria; Increase in Fev1 or FVC by 12% AND 200cc.Pts come to test BD freeNo response does not predict lack of benefitCan have partial responses, even in asthma
  39. 39. SPIROMETRY BRONCHOPROVOCATIONUsed to prove or disprove bronchial hyper responsiveness (BH) – asthma or bronchial dysfunctionNonselective Direct Stimulants Histamine – systemic side effects undesirable Methacholine – most commonly usedNonselective Indirect Stimulants AMP - may be more specific for airway inflammation than methacholine – causes release of histamine from mast cells Cold air, exercise, hyperventilation, nonisotonic solutionsSelective Stimulants NSAIDS, allergens, foods and food additives
  40. 40. SPIROMETRY BRONCHOPROVOCATIONMethacholine most standardized and common Logarithmically increasing doses inhaled per strict protocol. Drop in Fev1 by 20% considered positive Grades of certainty based on how much required to effect dropFalse negative response Bronchodilators, anticholinergics, anti-leukotrienes, theophylline or caffeine, steroids, can blunt response
  41. 41. SPIROMETRY BRONCHOPROVOCATIONShould not be a screening tool“Asthma” diagnosis is clinical; demonstration of BH is one piece of puzzle - Other entities cause BHAbsolute contraindications include Severe airflow limitation, recent MI, severe hypertension, aortic aneurysmRelative Moderate airflow limitation, pregnancy, lactation use of cholinesterase inhibitors of Myasthenia Gravis
  42. 42. SPIROMETRY QUESTIONS81 y/o caucasian maleFev1 2.04 litres 68%FVC 2.56 litres 65%Fev1/FVC .829 y/o Caucasian maleFev1 1.91 44%FVC 3.04 56%Fev1/FVC .63
  43. 43. MEASUREMENT OF LUNG VOLUMESRecall that spirometry can only measure volume from RV toTLC. Volume below RV is not “seen” by spirometry.
  44. 44. MEASUREMENT OF LUNG VOLUMESTwo CommonMethods ofMeasuring FRC Helium Dilution Plethysmography
  45. 45. MEASUREMENT OF LUNG VOLUMESHELIUM DILUTIONPt breathes at tidalvolume for severalminutes. Knowninitial volume andconcentration ofHelium before andafter equilibration.Lastly,Pt inspires from Will seriously underestimateFRC to TLC which is volume in obstruction,added to FRC especially bullous lungmeasurement disease.
  46. 46. MEASUREMENT OF LUNG VOLUMESBODYPLETHYSMOGRAPHYBOYLE’S LAWP1V1 = P2V2At FRC, shuttercloses at mouthand measurespressure atmouth and at boxduring slow Makes assumption that pressure at mouthpanting against equals pressure in alveoli, which may notshutter be true in obstructed patients
  47. 47. MEASUREMENT OF LUNG VOLUMESA large difference between plethysmography and helium dilution would suggest “non-communicating airspace”Valuable to measure FRC when spirometry yields a question regarding volumesOften difficult for elderly, severely obstructed, dyspneic
  48. 48. Nomogramalgorithm forseparatingobstructivefromrestrictivedefects
  49. 49. CARBON MONOXIDE DIFFUSING CAPACITY (DLCO)Known concentration of CO is inhaled insingle breath and held. CO binds avidly to Better term ishemoglobin and uptake is measured. Not “Transfer Factor”truly diffusion-limited and not true “capacity”
  50. 50. CARBON MONOXIDE DIFFUSING CAPACITY (DLCO)DECREASED DLCO INCREASED DLCO Loss of pulmonary  Polycythemia* vasculature  Alveolar hemorrhage, acute  PE, acute and chronic  Emphysema and chronic  Interstitial lung disease  Mild bronchitis, mild asthma  Lung resection Smoking Carbon Monoxide poisoning * DLCO can be Acute lung disease “corrected” for Anemia* hemoglobin if value is known
  51. 51. CARDIOPULMONARY EXERCISE TESTINGUsed for evaluation of exercise limitation Cardiac Pulmonary Poor conditioning Hyperventilation syndromes Vocal cord dysfunction

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