Simple Interpretation of Pulmonary Function tests

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Simple Interpretation of Pulmonary Function tests

  1. 1. Spirometry of Obstructive Lung Diseases Gamal Rabie Agmy, MD, FCCP Professor of Chest Diseases, Assiut University
  2. 2. Pulmonary Disorders Effects on Pulmonary Function Obstructive: Any process that interferes with air flow either into or out of the lungs. Large or small airways. Restrictive:  Any process that interferes with the bellows action of the lungs or chest wall.  Reduced lung volumes.
  3. 3. Differential Diagnosis: COPD and Asthma COPD Onset In mid-life Symptoms slowly progressive Long smoking history Dyspnea during exercise Largely Irreversible airflow limitation Asthma Onset early in life (often childhood) Symptoms vary from day to day Symptoms at night/early morning Allergy, rhinitis, and/or eczema also present Family history of asthma Largely reversible airflow limitation
  4. 4. Inflammatory Cascade in COPD & Asthma
  5. 5. Measures of Assessment and Monitoring of Asthma Asthma diagnosis criteria: Repeated variability in well-performed spirometic values (increase in FEV1 or FVC). Positive bronchodilator (BD) responses (increase in FEV1 or FVC ⩾12% and 200 mL from baseline). Positive methacholine challenge (20% fall in FEV1 at a dose ⩽8 μg/mL).
  6. 6. Objective lung function measurements in Asthma Spirometry: ▫ Forced Expiratory Maneuvers. Exhaled Nitric Oxide. Peak Flows.
  7. 7. GOLD 2013: Diagnosis of COPD  Key Indicators to Consider COPD Diagnosis: • SYMPTOMS 1 • Dyspnea-progressive (worsens over time and with exercise) • Chronic cough • Sputum • HISTORY OF EXPOSURE TO RISK FACTORS 2 3 • Tobacco smoke • Smoke from home cooking/heating fuels • Occupational dusts and chemical • FAMILY HISTORY OF COPD SPIROMETRY REQUIRED TO DIAGNOSE COPD Presence of a post-bronchodilator FEV1/FVC < 0.70 confirms the presence of persistent airflow limitation and thus of COPD. Adapted from GOLD 2013
  8. 8. Simple Interpretation of Pulmonary Function Tests Gamal Rabie Agmy, MD, FCCP Professor of Chest Diseases, Assiut University
  9. 9. Anatomy  Lungs comprised of   Airways Alveoli http://www.aduk.org.uk/gfx/lungs.jpg
  10. 10. The Airways    Weibel ER: Morphometry of the Human Lung. Berlin and New York: SpringerVerlag, 1963 Conducting zone: no gas exchange occurs  Anatomic dead space Transitional zone: alveoli appear, but are not great in number Respiratory zone: contain the alveolar sacs
  11. 11. The Alveoli    Murray & Nadel: Textbook of Respiratory Medicine, 3rd ed., Copyright © 2000 W. B. Saunders Company Approximately 300 million alveoli 1/3 mm diameter Total surface area if they were complete spheres 80 sq. meters (size of a tennis court)
  12. 12. Mechanics of Breathing  Inspiration   Active process Expiration Quiet breathing: passive  Can become active 
  13. 13. Pulmonary Function Tests  Airway function      Simple spirometry Forced vital capacity maneuver Maximal voluntary ventilation Maximal inspiratory/expiratory pressures Airway resistance  Lung volumes and ventilation     Functional residual capacity Total lung capacity, residual volume Minute ventilation, alveolar ventilation, dead space Distribution of ventilation
  14. 14. Pulmonary Function Tests   Diffusing capacity tests Blood gases and gas exchange tests      Blood gas analysis Pulse oximetry Capnography Cardiopulmonary exercise tests Metabolic measurements    Resting energy expenditure Substrate utilization Chemical analysis of exhaled breath
  15. 15. Terminology  Forced vital capacity (FVC):    Total volume of air that can be exhaled forcefully from TLC The majority of FVC can be exhaled in <3 seconds in normal people, but often is much more prolonged in obstructive diseases Measured in liters (L)
  16. 16. FVC  Interpretation of % predicted:     80-120% 70-79% 50%-69% <50% Normal Mild reduction Moderate reduction Severe reduction FVC
  17. 17. Terminology  Forced expiratory volume in 1 second: (FEV1)    Volume of air forcefully expired from full inflation (TLC) in the first second Measured in liters (L) Normal people can exhale more than 75-80% of their FVC in the first second; thus the FEV1/FVC can be utilized to characterize lung disease
  18. 18. FEV1  Interpretation of % predicted:      >75% Normal Mild 70-75% Mod 50-69 % Severe 35-49% Very severe < 35% FEV1 FVC
  19. 19. Terminology  Forced expiratory flow 2575% (FEF25-75)      Mean forced expiratory flow during middle half of FVC Measured in L/sec May reflect effort independent expiration and the status of the small airways Highly variable Depends heavily on FVC
  20. 20. FEF25-75  Interpretation of % predicted: >60%  40-60%  20-40%  <20%  Normal Mild obstruction Moderate obstruction Severe obstruction
  21. 21. Acceptability Criteria Good start of test  No coughing  No variable flow  No early termination  Reproducibility 
  22. 22. Changes in Lung Volumes in Various Disease States Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003
  23. 23. TLC TLC < 80% of predicted value = restriction.  TLC > 120% of predicted value = hyperinflation. 
  24. 24. Lung Volumes
  25. 25. Spirometry Spirometry should be performed after the administration of an adequate dose of a short acting inhaled bronchodilator (e.g. 400 ᶙg salbutamol) to minimize variability. A post-bronchodilator FEV 1/FVC <0.70 confirms the presence of airflow limitation that is not fully reversible. Where possible, values should be compared to age-related normal values to avoid overdiagnosis of COPD In the elderly.
  26. 26. Why Do We Need Spirometry in COPD? Spirometry is useful for: Screen individuals at risk for pulmonary disease. Confirmation of COPD diagnosis. Assessing severity of pulmonary dysfunction. Guiding selection of treatment. Assessing the effects of therapeutic interventions.
  27. 27. Who Should Be Screened for COPD? Consider COPD, and perform spirometry, if any of these indicators are present in an individual over age 40. ▫ Dyspnea that is progressive, usually worse with exercise, and persistent. ▫ Chronic cough (may be intermittent and unproductive). ▫ Chronic sputum. ▫ History of tobacco smoke exposure. ▫ Exposure to occupational dusts and chemicals. ▫ Risk factors. ▫ Exposure to smoke from home cooking and heating fuels.
  28. 28. Spirometry Origin Most basic of Pulmonary Function Tests Clinical Tools Origin - Mid 1800' s ▫ John Hutchinson. ▫ Water-sealed spirometry to measure vital capacity (VC).
  29. 29. Reasons for Performing Spirometry Diagnostic Purposes. Monitoring Lung Disease. Assessing Disability.
  30. 30. Spirometry Spirometry with flow volume loops assesses the mechanical properties of the respiratory system by measuring expiratory volumes and flow rates. ▫ Maximal inspiratory and expiratory effort. ▫ At least 3 tests of acceptable effort are performed to ensure reproducibility.
  31. 31. 21st Century Spirometry Measurements of: Forced Vital Capacity (FVC). Forced Expiratory Volume in one second (FEV1). Forced Expiratory Volume in six seconds (FEV6). Forced Expiratory Flow over various Intervals (FEFx). Peak Expiratory Flow (PEF).
  32. 32. Definitions and Terms FEV1 - forced expiratory volume 1 - the volume of air that is forcefully exhaled in one second. FEV6 - forced expiratory volume 6 - the volume of air that Is forcefully exhaled in six seconds. FVC- forced vital capacity- the volume of air that can be maximally forcefully exhaled. FEV1/FVC- ratio of FEV1 to FVC, expressed as a percentage.
  33. 33. Definitions and Terms FEV/FVC- ratio of FEV6 to FVC, expressed as a percentage. FEF25 -75 - forced expiratory flow - the average forced expiratory flow during the mid (25 - 75%) portion of the FVC. PEF- peak expiratory flow rate - the peak flow rate during expiration.
  34. 34. Spirometry Flow volume loops provide a graphic illustration of a patient's spirometric efforts. Flow is plotted against volume to display a continuous loop from inspiration to expiration. The volume versus time curve is a an alternative way of plotting spirometric results. The overall shape of the flow volume loop is important in Interpreting spirometric results.
  35. 35. Acceptability & Repeatability
  36. 36. Acceptability At least three (3) acceptable maneuvers Good start to the test. No hesitation or coughing for the 1st second. FVC lasts at least 6 seconds with a plateau of at least 1 second. No valsalva maneuver or obstruction of the mouthpiece. FIVC shows apparent maximal effort.
  37. 37. Repeatability Repeatability criteria act as guideline to determine need for additional efforts. ▫ Largest and 2nd largest FVC must be within 150 mL. ▫ Largest and 2nd largest FEV 1 must be 150 mL. ▫ PEF values may be variable (within 15%). If three acceptable reproducible maneuvers are not recorded, up to B attempts may be recorded.
  38. 38. Spirometry Value Spirometry is typically reported in both absolute values and as a predicted percentage of normal. Normal values vary and are dependent on: ▫ ▫ ▫ ▫ Gender, Race, Age, and Height.
  39. 39. Reporting Standards Largest FVC obtained from all acceptable efforts should be reported. Largest FEV1 obtained from all acceptable trials should be reported. May or may not come from largest FVC effort. All other flows, should come from the effort with the largest sum of FEV 1 & FVC. PEF should be the largest value obtained from at least 3 acceptable maneuvers.
  40. 40. Results Reporting Example
  41. 41. Report Format Report should also include: ▫ ▫ ▫ ▫ ▫ ▫ Age on testing day. Height (standing without shoes). Weight (without shoes). Gender. Race or ethnic origin. Technologist comment section.
  42. 42. FEV1 Results for Asthma
  43. 43. FEV 1 Severity Results for Asthma
  44. 44. At Risk for COPD Spirometric classification of airflow limitation (in patients with FEV1/FVC<0.70). ▫ ▫ ▫ ▫ GOLD 1 GOLD 2 GOLD 3 GOLD 4 Adapted from GOLD 2013 (Mild; FEV1 ≥80% predicted). (Moderate; 50% ≤FEV1 <80% predicted). (Severe; 30% ≤FEV1 <50% predicted). (Very severe; FEV1 <30% predicted).
  45. 45. Pre & Post Bronchodilator Studies B-Adrenergic aerosols are most common form for testing. Standardize. ▫ Drug. ▫ Dosage. ▫ Delivery Device. Minimum of 15 minutes between pre and post tests.
  46. 46. Pre & Post Bronchodilator Studies: Withholding Medications
  47. 47. Pre & Post Bronchodilator Studies: Interpretations Determined based on improvement of FEV1. Commonly expressed as Percent Change. % Change = Post FEV 1 - Pre FEV1 x 100 Pre FEV1
  48. 48. Reversibility Reversibility of airways obstruction can be assessed with the use of bronchodilators. > 12% increase in the FEV1 and 200 ml improvement in FEV1 OR > 12% increase in the FVC and 200 ml improvement in FVC.
  49. 49. Spirometry
  50. 50. Asthma Challenge Testing Spirometry can be used to detect the bronchial hyperreactivity that characterizes asthma. Increasing concentrations of histamine or methacholine. Patients with asthma will demonstrate symptoms and produce spirometric results consistent with airways obstruction at much lower threshold concentration than normals.
  51. 51. Bronchial Provocation for Asthma
  52. 52. Spirometry Indications — Diagnosis  Evaluation of signs and symptoms - SOB, exertional dyspnea, chronic cough  Screening at-risk populations  Monitoring pulmonary drug toxicity  Abnormal study - CXR, EKG, ABG, hemoglobin  Preoperative assessment
  53. 53. Spirometry Indications — Diagnosis  Evaluation of signs and symptoms - SOB, exertional dyspnea, chronic cough  Screening at-risk populations Smokers > 45yo  Monitoring pulmonary drug toxicity & current) (former  Abnormal study - CXR, EKG, ABG, hemoglobin  Preoperative assessment
  54. 54. Spirometry Indications — Diagnosis  Evaluation of signs and symptoms - SOB, exertional dyspnea, chronic cough  Screening at-risk populations  Evaluation of occupational symptoms  Monitoring pulmonary drug toxicity  Abnormal study - CXR, EKG, ABG, hemoglobin  Preoperative assessment
  55. 55. Spirometry Indications — Prognostic ■ Assess severity ■ Follow response to therapy ■ Determine further treatment goals ■ Referral for surgery ■ Disability
  56. 56. 1-First Step, Check quality of the test 1- Start: *Good start: Extrapolated volume (EV) < 5% of FVC or 0.15 L *Poor start: Extrapolated volume (EV) ≥5% of FVC or ≥ 0.15 L 2- Termination: *No early termination :Tex ≥ 6 s *Early termination : Tex < 6 s
  57. 57. 2- Look at …………FEV1/FVC < N(70%) Obstructive or Mixed ≥ N(70%) Restrictive or Normal 3- Look at FEV1 To detect degree Mild > 70% Mod 50-69 % Severe 35-49% Very severe < 35%
  58. 58. 4- Postbronchodilator FEV1/FVC > 70% asthma < 70% COPD
  59. 59. 5- Reversibility test of FEV1 > 12%, 200 ml Reversible (asthma) < 12% ,200 ml Ireversible (COPD) 6- Look at TLC ≥ 80-120% Pure obstruction < 80% Mixed
  60. 60. 2- Look at …………FEV1/FVC < N(70%) ≥ N(70%) Obstructive or Mixed Restrictive or Normal 3- Look at FVC ≥ N(80%) Normal or SAWD 4-Look at FEF25/75 > 50% Normal < 50% SAWD < N(80%) Restrictive
  61. 61. Patterns of Abnormality Obstructive low FEV1 relative to FVC, low PEF, low FEV1%FVC R eco rd ed Pred icted SR % Pred 0.56 3.25 -5.3 17 1.65 4.04 -3.9 41 FEV 1 % FV C 34 78 -6.1 44 PEF 2.5 8.28 -4.8 30 FEV 1 FV C Restriction low FEV1 & FVC, high FEV1%FVC R eco rd ed FEV 1 FV C FEV 1 % FV C PEF Pred icted SR % Pred 1.49 2.52 -2.0 59 1.97 3.32 -2.2 59 76 74 0.3 103 8.42 7.19 1.0 117 high PEF early ILD low PEF late ILD
  62. 62. Patterns of Abnormality Upper Airway Obstruction low PEF relative to FEV1 R eco rd ed Pred icted SR % Pred 2.17 2.27 -0.3 96 2.68 2.70 0.0 99 81 76 0.7 106 PEF 2.95 5.99 -3.4 49 FEV 1 /PEF 12.3 FEV 1 FV C FEV 1 % FV C Discordant PEF and FEV1 High PEF versus FEV1 = early interstitial lung disease (ILD) Low PEF versus FEV1 = upper airway obstruction Concordant PEF and FEV1 Both low in airflow obstruction, myopathy, late ILD
  63. 63. Flow Common FVL Shapes Volume Normal Hesitation Young or quitter Knee Poor effort Coughing
  64. 64. 12 Asthma Flow in L/s 10 concave FV curve intrapulmonary airflow obstruction 8 6 4 2 0 0 1 2 3 4 5 Litres 6
  65. 65. Restrictive 12 F 19 yrs 1.64m FVC 2.41 L -3.42 SR FEV 2.41 L -2.62 SR FEV% 100 +2.23 SR PEF 5.55L/s -2.00 SR F/P 7.2 RT 116 ms 10 8 Flow in L/s 6 4 2 0 0 -2 -4 -6 -8 1 2 3 4 5 Litres 6
  66. 66. COPD 10 8 pressure dependent airways collapse 6 Flow in L/s 4 2 0 0 -2 -4 -6 1 2 3 4 5 Litres
  67. 67. Poorly co-ordinated start EV = large Rise Time = 496 ms Irregular shape Poorly repeatable 12 10 8 6 Flow in L/s 4 2 0 0 -2 -4 -6 -8 -10 1 2 3 4 5 6 Litres
  68. 68. Upper Airway Obstruction 6 Expiratory Age 40 yrs FVC 3.52 L FEV1 3.0 L 0.74 SR PEF 4.57 L/s 4 0.84 SR -2.18 SR FEV/PEF = 10.9 Flow in L/s 2 0 0 1 2 4 5 6 Volume in Litres -2 -4 -6 3 Inspiratory FEV1 in mls > 8 PEF in L/min
  69. 69. Upper Airway Obstruction 12 Male aged 62 Height 1.68m 10 R e co rd e d SR 2.23 2.94 2.1 to 3.8 -1.4 FV C 3.40 3.71 2.7 to 4.7 -0.5 66 76 64 to 88 -1.5 P EF 2.85 7.81 5.8 to 9.8 -4.1 FEV 1 /P EF 13.1 FEV 1 % FV C 6 Flow in L/s R an ge FEV 1 8 P re d icte d 4 2 0 0 -2 -4 -6 1 2 3 4 5 6 Volume in Litres
  70. 70. Variable UAO Inspiration Expiration +ve -ve -ve Extra-thoracic UAO worse on insp. +ve Intra-thoracic UAO worse on exp.
  71. 71. Intra-thoracic UAO 12 Age 65 Female FVC 2.97 L FEV1 2.26 L FEV1% 76% PEF 3.4 L·s-1 F/P 11.1 10 Flo w in L /s 8 6 4 2 0 0 -2 -4 -6 -8 1 2 3 4 5 L ite rs 6 1.3 SR 0.6 SR -0.1 SR -2.5 SR RT 455 ms
  72. 72. Upper Airway Obstruction • Variable extrathoracic obstructions 1. 2. 3. 4. vocal cord paralysis, thyromegaly, tracheomalacia, or Neoplasm • Large airways variable intrathoracic obstructions 1. 2. tracheomalacia or neoplasm • Fixed obstruction 1. 2. tracheal stenosis, foreign body, or 3. neoplasm.
  73. 73. Obstruction, Restriction, Mixed
  74. 74. Variable Extrathoracic Upper Airway Obstruction
  75. 75. Fixed Upper Airway Obstruction
  76. 76. True Restrictive Disorders Intraparenchymal Interstitial Infilterative Chest Wall Diffuse alveolar Pleural Skeletal Neuromuscular Reduced TLC.FRC,RV,VC and normal to high FEV1/FVC DLVA,Dlcoc or both DLVc parynhymal If normal Chest wall or neuromuscular
  77. 77. Pseudorestrictive Disorders Normally: IC/ERV=2-3/1 True restrictive: IC/ERV=<2/1 Pseudorestrictive: IC/ERV=6/1
  78. 78. Pseudorestrictive Disorders Asthma is a disorder characterized by increased reactivity of the airways. Patients with asthma have recurrent or persistent airflow obstruction, which is reversible either spontaneously or with appropriate therapy. An obstructive pattern is most often present, recognized by reduced forced expiratory volume in 1 s (FEV1), and FEV1 to forced vital capacity (FEV1/FVC) or FEV1/vital capacity (VC) ratio. Patients may have normal spirometry between attacks. In some patients, the FVC may be reduced due to air trapping, resulting in pseudorestriction on spirometry in the presence of increased or normal total lung capacity (TLC), increased functional residual capacity (FRC) and increased residual volume (RV). We have reported 12 asthmatic patients with reduced VC and no increase in RV, i.e., a true restrictive impairment [Gill et al. Chest 2012)
  79. 79. Pseudorestrictive Disorders Obesity: *Early airway closure (low ERV & high RV) *FRC is more reduced than TLC&VC *Low FEF50% FEF75%, FEF25-75%, ,
  80. 80. Pseudorestrictive Disorders Neuromuscular Disease: *FRC normal *IC&ERV decreased *Decreased TLC *Increased RV *A-aO2 gradient normal *MIP&MEP decreased
  81. 81. Pseudorestrictive Disorders Asthma: *FRC &TLC increased *Improvement of FEV1&FVC with bronchodilators *Positive bronchoprovacation test *Increased diffusing capacity and DLco/VA
  82. 82. Pseudopseudorestrictive Patients with obstructive diseases who do not complete expiratory effort of FVC. This may lead to a below normal FEV1 and FVC with pseudonormalization of ratio.
  83. 83. Mixed Disorder *Sarcoidosis *Rhematoid *Advanced IPF *Bronchiectasis *BOOP in smokers
  84. 84. Obstructive Pattern ■ Decreased FEV1 ■ Decreased FVC ■ Decreased FEV1/FVC - <70% predicted ■ FEV1 used to follow severity in COPD
  85. 85. Obstructive Lung Disease — Differential Diagnosis  Asthma  COPD - chronic bronchitis - emphysema  Bronchiectasis  Bronchiolitis  Upper airway obstruction
  86. 86. Restrictive Pattern  Decreased FEV1  Decreased FVC  FEV1/FVC normal or increased
  87. 87. Restrictive Lung Disease — Differential Diagnosis  Pleural  Parenchymal  Chest wall  Neuromuscular
  88. 88. Spirometry Patterns
  89. 89. Bronchodilator Response  Degree to which FEV1 improves with inhaled bronchodilator  Documents reversible airflow obstruction  Significant response if: - FEV1 increases by 12% and >200ml  Request if obstructive pattern on spirometry
  90. 90. Flow Volume Loop  “Spirogram”  Measures forced inspiratory and expiratory flow rate  Augments spirometry results  Indications: evaluation of upper airway obstruction (stridor, unexplained dyspnea)
  91. 91. Flow Volume Loop
  92. 92. Upper Airway Obstruction  Variable intrathoracic obstruction  Variable extrathoracic obstruction  Fixed obstruction
  93. 93. Upper Airway Obstruction
  94. 94. Lung Volumes  Measurement: - helium - nitrogen washout - body plethsmography  Indications: - Diagnose restrictive component - Differentiate chronic bronchitis from emphysema
  95. 95. Lung Volumes – Patterns  Obstructive - TLC > 120% predicted - RV > 120% predicted  Restrictive - TLC < 80% predicted - RV < 80% predicted
  96. 96. Diffusing Capacity  Diffusing capacity of lungs for CO  Measures ability of lungs to transport inhaled gas from alveoli to pulmonary capillaries  Depends on: - alveolar—capillary membrane - hemoglobin concentration - cardiac output
  97. 97. Diffusing Capacity  Decreased DLCO (<80% predicted)  Increased DLCO (>120-140% predicted)  Obstructive lung disease  Asthma (or normal)  Parenchymal disease  Pulmonary hemorrhage  Pulmonary vascular disease  Polycythemia  Anemia  Left to right shunt
  98. 98. DLCO — Indications  Differentiate asthma from emphysema  Evaluation and severity of restrictive lung disease  Early stages of pulmonary hypertension
  99. 99. Bronchoprovocation  Useful for diagnosis of asthma in the setting of normal pulmonary function tests  Common agents: - Methacholine, Histamine, others  Diagnostic if: ≥20% decrease in FEV1
  100. 100. PFT Patterns  Emphysema  Chronic Bronchitis  FEV1/FVC <70%  FEV1/FVC <70%  “Scooped” FV curve  “Scooped” FV curve  TLC increased  TLC normal  Increased compliance  Normal compliance  DLCO decreased  DLCO usually normal
  101. 101. PFT Patterns  Asthma  FEV1/FVC normal or decreased  DLCO normal or increased But PFTs may be normal  bronchoprovocation

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