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Pulmonary function testing


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    FEV1 is decreased out of proportion to FVC, which causes the ratio to decrease as well.
  • This is not a complete list, just some of the most common diseases that should be on your differential for obstructive lung disease.
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    FEV1 decreases in proportion to decrease in FVC, so ratio remains normal or even slightly increased
  • Restrictive lung disease is made up of intrinsic lung disease (causes inflammation and scarring (interstitial lung diseases) or fill the airspaces w/ debris, inflammation (exudate); extrinsic causes are chest wall or pleural diseases that mechanically compress the lung and prevent expansion. Neuromuscular causes decreases ability of respiratory muscles to inflate and deflate the lungs.
  • Lack of observed response to bronchodilator does not preclude use, b/c patients may have symptomatic benefit.
    Can give 6-8wk trial of bronchodilator and/or inhaled corticosteroids (ICS) and reassess clinically, can also obtain FEV1 at that time.
  • Have patient breath out at max effort, then breath in quickly at max effort, creates a loop w/ differing patterns.
    Upper airway = pharynx, larynx, trachea.
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    Vocal cord dysfunction: variable extrathoracic obstruction.
    Tracheal stenosis: fixed obstruction (hx frequent intubations).
    Rapid rise to peak flow rate, followed by fall in flow as pt exhales toward residual volume. Inspiratory curve is symmetrical.
  • Example of someone grabbing trachea—causes problems w/ inspiration and expiration = fixed obstruction
    Vocal cord dysfunction: variable extrathoracic obstruction.
    Endobronchial carcinoma: variable intrathoracic obstruction. (Rare to diagnose this on flow volume loop).
  • FVC is decreased in both obstructive and restrictive disease, so usually need to obtain lung volumes to see if restrictive component present (increased TLC).
  • Measure of gas exchange at alveolar-capillary membrane.
    Changes in DLCO are one of the earliest signs of interstitial lung disease (ILD).
  • Pulmonary vascular disease = pulmonary emboli, pulmonary HTN.
    Low DLCO is also a major predictor of desaturation during exercise.
  • So you have restrictive disease by spirometry and lung volumes. You get a DLCO and see it is normal. Thinking back to your differential diagnosis of restrictive lung disease (what are the four things on your differential?), what can you probably rule out? Answer = Interstitial lung disease.
    This is where you would order max respiratory pressures, to evaluate for NM disease. Max inspiratory pressures are recorded as patientt is breathing through a blocked tube, also done for expiration. Should be decreased in NM disease.
  • Can always send patient home and tell them to come back when having symptoms, but this delays diagnosis. Another alternative is measure peak flow variability at home.
    If suspected asthma but has not responded to therapy, think of obtaining flow volume loop to see if there is vocal cord dysfunction = variable extrathoracic obstruction.
  • Don’t need a DLCO, but if were decreased would make you think emphysema, if normal then chronic bronchitis.
  • IF restrictive pattern, you’re going to want to get DLCO b/c it tells you whether the restriction is due to parenchymal disease (which will change your management), or NM, pleural or CW disease
  • Remember that DLCO should be normal in chronic bronchitis because it affects the more proximal airways which is not where your gas exchange takes place.
  • In COPD patients, the FEV1 is used to classify severity of obstructive lung disease, and followed to assess progression.
  • This is kind of tricky b/c technically the recommendation is if no obstruction, then no bronchodilator (can omit this since costs an extra $40-50). Flow volume loops will usually come w/ your testing but you need to ask if you want the full max inspiratory and expiratory curves.
  • Intrinsic lung diseases that cause inflammation or scarring of the lung tissue OR that fill the airspaces w/ exudate or debris (pneumonitis or pneumonia) can cause decreased lung volumes and DLCO but NOT increased DLCO. This only comes from blood in the alveoli, polycythemia, L to R shunt or possibly asthma. So if you see bilateral pulmonary infiltrates on CXR and you get a DLCO that is elevated, then there is only one answer alveolar hemorrhage.
  • Transcript

    • 1. Pulmonary Function Testing The Basics of Interpretation
    • 2. Anatomy • Lungs comprised of – Airways – Alveoli
    • 3. The Airways • 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 Weibel ER: Morphometry of the Human Lung. Berlin and New York: SpringerVerlag, 1963
    • 4. The Alveoli • Approximately 300 million alveoli • 1/3 mm diameter • Total surface area if they were complete spheres 85 sq. meters (size of a tennis court) Murray & Nadel: Textbook of Respiratory Medicine, 3rd ed., Copyright © 2000 W. B. Saunders Company
    • 5. Pulmonary function test : Group of procedures that measure the function of the lungs 1. 2. 3. 4. Spirometry Lung volumes Gas transfer Bronchial chalenge
    • 6. Spirometry • Measurement of the pattern of air movement into and out of the lungs during controlled ventilatory maneuvers. • Often done as a maximal expiratory maneuver
    • 7. Spirometry Measures flow, volumes  Volume vs. Time  Can determine: - Forced expiratory volume in one second (FEV1) - Forced vital capacity (FVC) - FEV1/FVC - Forced expiratory flow 25%-75% (FEF25-75)
    • 8. What is a spirometry ?? Spirometry is a measure of airflow and lung volumes during a forced expiratory maneuver from full inspiration
    • 9. 1. Volume Time Graph 2. Flow-volume loops
    • 10. Lung Volumes
    • 11. 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)
    • 12. FVC • Interpretation of % predicted: – – – – 80-120% 70-79% 50%-69% <50% Normal Mild reduction Moderate reduction Severe reduction FVC
    • 13. 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
    • 14. FEV1 • Interpretation of % predicted: – – – – >75% 60%-75% 50-59% <49% Normal Mild obstruction Moderate obstruction Severe obstruction FEV1 FVC
    • 15. 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
    • 16. Spirometry
    • 17. Volume Time Graph The volume is plotted against the time, it displays the expiration.
    • 18. 1. FVC 2. FEV1 3. FEV1/FVC 4. FEF25% 5. FEF75%
    • 19. Forced Vital Capacity (FVC) The total amount of air expired as quickly as possible after taking the deepest possible breath.
    • 20. FEV1 : Volume of air which can be forcibly exhaled from the lungs in the first second of a forced expiratory maneuver.
    • 21. FEV1/FVC Ratio of FEV1 to FVC : It indicates what percentage of the total FVC was expelled from the lungs during the first second of forced exhalation This value is critically important in the diagnosis of obstructive and restrictive diseases
    • 22. FEF25% Amount of air that was forcibly expelled in the first 25% of the total forced vital capacity test. FEF75% The amount of air expelled from the lungs during the first (75%) of the forced vital capacity test. FEF25%-75% The amount of air expelled from the lungs during the middle half of the forced vital capacity test.
    • 23. Normal Spirometry
    • 24. Obstructive Pattern ■ Decreased FEV1 ■ Decreased FVC ■ Decreased FEV1/FVC - <70% predicted ■ FEV1 used to follow severity in COPD
    • 25. Obstructive Lung Disease — Differential Diagnosis  Asthma  COPD - chronic bronchitis - emphysema  Bronchiectasis  Bronchiolitis  Upper airway obstruction
    • 26. Restrictive Pattern  Decreased FEV1  Decreased FVC  FEV1/FVC normal or increased
    • 27. Restrictive Lung Disease — Differential Diagnosis  Pleural  Parenchymal  Chest wall  Neuromuscular
    • 28. Spirometry Patterns
    • 29. 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
    • 30. Flow-volume loops
    • 31. Flow Volume Loop  “Spirogram”  Measures forced inspiratory and expiratory flow rate  Augments spirometry results  Indications: evaluation of upper airway obstruction (stridor, unexplained dyspnea)
    • 32. Flow-Volume Loop • Illustrates maximum expiratory and inspiratory flowvolume curves • Useful to help characterize disease states (e.g. obstructive vs. restrictive) Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003
    • 33. Flow Volume Loop
    • 34. Obstructive Disorders • Characterized by a limitation of expiratory airflow – Examples: asthma, COPD • Decreased: FEV1, FEF25-75, FEV1/FVC ratio (<0.8) • Increased or Normal: TLC
    • 35. Restrictive Lung Disease • Characterized by diminished lung volume due to: – change in alteration in lung parenchyma (interstitial lung disease) – disease of pleura, chest wall (e.g. scoliosis), or neuromuscular apparatus (e.g. muscular dystrophy) • Decreased TLC, FVC • Normal or increased: FEV1/FVC ratio
    • 36. Upper Airway Obstruction  Variable intrathoracic obstruction  Variable extrathoracic obstruction  Fixed obstruction
    • 37. Fixed obstruction 1. Post intubation stenosis 2. Goiter 3. Endotracheal neoplasms 4. Bronchial stenosis Maximum airflow is limited to a similar extent in both inspiration and expiration
    • 38. Variable extrathoracic Obstruction 1. Bilateral and unilateral vocal cord paralysis 2. Vocal cord constriction 3. Reduced pharyngeal crosssectional area 4. Airway burns The obstruction worsens in inspiration because the negative pressure narrows the trachea and inspiratory flow is reduced to a greater extent than expiratory flow
    • 39. In variable intrathoracic obstruction 1. Tracheomalacia 2. Polychondritis 3. Tumors of the lower trachea or main bronchus. The narrowing is maximal in expiration because of increased intrathoracic pressure compressing the airway. The flow volume loop shows a greater reduction in the expiratory phase
    • 40. Upper Airway Obstruction
    • 41. Lung Volumes  Measurement: - helium - nitrogen washout - body plethsmography  Indications: - Diagnose restrictive component - Differentiate chronic bronchitis from emphysema
    • 42. Lung Volumes – Patterns  Obstructive - TLC > 120% predicted - RV > 120% predicted  Restrictive - TLC < 80% predicted - RV < 80% predicted
    • 43. 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
    • 44. Diffusing Capacity  Decreased DLCO (<80% predicted)  Increased DLCO (>120-140% predicted)  Asthma (or normal)  Obstructive lung disease  Pulmonary hemorrhage  Parenchymal disease  Polycythemia  Pulmonary vascular disease  Anemia  Left to right shunt
    • 45. DLCO — Indications  Differentiate asthma from emphysema  Evaluation and severity of restrictive lung disease  Early stages of pulmonary hypertension
    • 46. Case 1 CC/HPI: A 36yo WM, nonsmoker, presents to your clinic with c/o episodic cough for 6mo. Also reports occasional wheezing and dyspnea with exertion during softball practice. Exam: Heart RRR, no murmurs; Lungs CTAB, no labored breathing Based on your exam and a thorough review of systems, you suspect asthma and decide to order spirometry for further evaluation.
    • 47. Continued… PFTs: FEV1 FEV1/FVC 86% predicted 82% predicted Flow Volume Loop: normal inspiratory and expiratory pattern You still suspect asthma. What is your next step in the workup of this patient?
    • 48. 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
    • 49. Continued… SYMPTOMS ↓ PFTs ↓ OBSTRUCTION? ↓ ↓ YES NO ↓ ↓ TREAT BRONCHOPROVOCATION ↓ ↓ Obstruction? No Obstruction? TREAT Other Diagnosis
    • 50. Obstructive Pattern — Evaluation  Spirometry  FEV1, FVC: decreased  FEV1/FVC: decreased  FV Loop “scooped”  Lung Volumes  TLC, RV: increased  Bronchodilator responsiveness (<70% predicted)
    • 51. Restrictive Pattern – Evaluation  Spirometry  FVC, FEV1: decreased  FEV1/FVC: normal or increased  FV Loop “witch’s hat”  DLCO decreased  Lung Volumes  TLC, RV: decreased
    • 52. 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
    • 53. PFT Patterns  Asthma  FEV1/FVC normal or decreased  DLCO normal or increased But PFTs may be normal  bronchoprovocation
    • 54. Pulmonary Function Testing Which of the following is used to follow disease severity in COPD patients? a. b. c. d. e. Total lung capacity (TLC) Degree of responsiveness to bronchodilators Forced vital capacity (FVC) Forced expiratory volume in 1 second Diffusing capacity (DLCO)
    • 55. Pulmonary Function Testing Which of the following is used to follow disease severity in COPD patients? a. b. c. d. e. Total lung capacity (TLC) Degree of responsiveness to bronchodilators Forced vital capacity (FVC) Forced expiratory volume in 1 second Diffusing capacity (DLCO)
    • 56. Pulmonary Function Testing A 36yo WF, non-smoker, presents to your office for follow-up of ‘recurrent bronchitis.’ You suspect asthma and decide to order spirometry. Which of the following would you include in your prescription for testing? a. b. c. d. e. Diffusing Capacity (DLCO) If no obstruction present, add trial of bronchodilator If no obstruction present, perform methacholine challenge Flow volume loop b and c
    • 57. Pulmonary Function Testing A 36yo WF, non-smoker, presents to your office for follow-up of ‘recurrent bronchitis.’ You suspect asthma and decide to order spirometry. Which of the following would you include in your prescription for testing? a. b. c. d. e. Diffusing Capacity (DLCO) If no obstruction present, add trial of bronchodilator If no obstruction present, perform methacholine challenge Flow volume loop b and c
    • 58. Pulmonary Function Testing A 68yo HM is admitted to the ICU with acute respiratory distress. A CXR obtained in the ED demonstrates bilateral pulmonary infiltrates, and his DLCO is elevated. What is the most likely diagnosis? a. b. c. d. e. Pulmonary edema Aspiration pneumonitis Pulmonary emboli Alveolar hemorrhage Interstitial lung disease
    • 59. Pulmonary Function Testing A 68yo HM is admitted to the ICU with acute respiratory distress. A CXR obtained in the ED demonstrates bilateral pulmonary infiltrates, and his DLCO is elevated. What is the most likely diagnosis? a. b. c. d. e. Pulmonary edema Aspiration pneumonitis Pulmonary emboli Alveolar hemorrhage Interstitial lung disease
    • 60. Contraindications
    • 61.           Hemoptysis of unknown origin Pneumothorax Unstable angina pectoris Recent myocardial infarction Thoracic aneurysms Abdominal aneurysms Cerebral aneurysms Recent eye surgery (increased intraocular pressure during forced expiration) Recent abdominal or thoracic surgical procedures History of syncope associated with forced exhalation
    • 62. Obstructive V/S restrictive lung disease ???
    • 63. Obstructive Lung Diseases
    • 64. Common Obstructive Lung Diseases • Asthma • COPD (chronic bronchitis, emphysema and the overlap between them). • Cystic fibrosis.
    • 65. -Airflow is reduced because the airways narrow and the FEV1 is reduced -Spirogram may continue to rise for more than 6 seconds because lung take longer to empty -FVC may also be reduced because gas is trapped behind obstructed bronchi due to increase in intrathoracic pressure during maneuver compresses airways causing early airway closure and gas trapping but this reduction to a lesser extent than FEV1
    • 66. FEV1 ≥ 80% of predicted Normal FEV1 60-80% of predicted mild obst. FEV1 40-60% of predicted moderate FEV1 ≤ 40% of predicted severe The cardinal feature is FEV1/FVC ratio If the ratio less than 70 consider obstructed disease . *Predictors: Sex, Age, Ht
    • 67. Flow volume loop in Obstructive lung disease
    • 68. Asthma  Peak expiratory flow reduced so maximum height of the loop is reduced  Airflow reduces rapidly with the reduction in the lung volumes because the airways narrow and the loop become concave  Concavity may be the indicator of airflow obstruction and may present before the change in FEV1 or FEV1/FVC
    • 69. Emphysema Airways may collapse during forced expiration because of destruction of the supporting lung tissue causing very reduced flow at low lung volume and a characteristic (dog-leg) appearance to the flow volume curve
    • 70. Reversibility • Improvement in FEV1 by 12-15% or 200 ml in repeating spirometry after treatment with Sulbutamol 2.5mg or ipratrobium promide by nebuliser after 15-30 minutes • Reversibility is a characterestic feature of B.Asthma • In chronic asthma there may be only partial reversibility of the airflow obstruction • While in COPD the airflow is irriversible although some cases showed significant improvement.
    • 71. Interpretation of PFTs Step 1. Look at the Flow-Volume loop to determine acceptability of the test, and look for upper airway obstruction pattern. Step 2. Look at the FEV1 to determine if it is normal (≥ 80% predicted). Step 3. Look at FVC to determine if it is within normal limits (≥ 80%). Step 4. Look at the FEV1/FVC ratio to determine if it is within normal limits (≥ 70%).
    • 72. Step 5. Look at FEF25-75% (Normal (≥ 60%) • If FEV1, FEV1/FVC ratio, and FEF25-75% all are normal, the patient has a normal PFT. • If both FEV1 and FEV1/FVC are normal, but FEF2575% is ≤ 60% ,then think about early obstruction or small airways obstruction.
    • 73. • If FEV1 ≤ 80% and FEV1/FVC ≤ 70%, there is obstructive defect, if FVC is normal, it is pure obstruction. If FVC ≤ 80% , possibility of additional restriction is there. • If FEV1 ≤ 80% , FVC ≤ 80% and FEV1/FVC ≥ 70% , there is restrictive defect, get lung volumes to confirm.
    • 74. Small Airways obstruction • Diseases affecting primarily the small (peripheral) airways can be extensive yet not affect the FEV1(e.g. early COPD, interstitial granulomatous disorders). • Small airways status is reflected by the FEF25-75% (mid-range flow), best determined from the flowvolume loop. • Some patients have normal spirometry with the exception of a reduced FEF25-75%, this is suggestive of possible small airways dysfunction and potentially early obstruction.
    • 75. Effect of Smoking: • Smoking in patients with COPD is associated with decline in FEV1 of 90-150 mL/year • Smoking cessation is (associated with increase in FEV1 for first year) followed with a decline of only 30 mL/year
    • 76. Restrictive Lung Diseases
    • 77. A. Intrinsic Restrictive Lung Disorders 1. 3. 4. Sarcoidosis Idiopathic pulmonary fibrosis Interstitial pneumonitis Tuberculosis 5. 6. Pnuemonectomy (loss of lung) Pneumonia 2.
    • 78. B. Extrinsic Restrictive Lung Disorders 1. 2. 3. 4. 5. 6. 7. 8. Scoliosis, Kyphosis Ankylosing Spondylitis Pleural Effusion Pregnancy Gross Obesity Tumors Ascites Pain on inspiration - pleurisy, rib fractures
    • 79. C. Neuromuscular Restrictive Lung Disorders 1. 2. 3. 4. 5. 6. Generalized Weakness – malnutrition Paralysis of the diaphragm Myasthenia Gravis Muscular Dystrophy Poliomyelitis Amyotrophic Lateral Sclerosis
    • 80. • Full expantion of the lung is limited and therefore the FVC is reduced • FEV1 may be reduced because the stiffness of fibrotic lungs increases the expiratory pressure • FEV1/FVC will be Normal or Increased *if you suspect restrictive pattern you must check TLC
    • 81. Flow volume loop in Restrictive lung disease
    • 82. Flow volume loop in Restrictive lung disease :  Full lung expantion is prevented by fibrotic tissue in the lung parenchyma and the FVC is reduced .  Elastic recoil may increased by fibrotic tissue lead to increase the airflow  Both FEV1 and FVC may be reduced because the lungs are small and stiff ,but the peak expiratory flow may be preserved or even higher than predicted leads to tall,narrow and steep flow volume loop in expiratory phase.
    • 83. Obstructive & restrictive defects Parameter FEV1 FVC FEV1/FVC Obstruction Reduced Normal Reduced Restriction Reduced Reduced Normal
    • 84. A breathless 23-year-old woman has the following lung function tests: FEV1 1.1L (60%)/ FVC 1.3 L (55%)/ FEV1/FVC ratio = 84%/ TLC = 66% predicted/ RV = 57% predicted/ TLCO = 55% predicted/ KCO = 110% predicted What is the most likely diagnosis? A : Acute sickle crisis B : systemic lupus erythematosus (SLE) pneumonitis C : Scoliosis D : Asthma E : Cystic fibrosis.
    • 85. C : Scoliosis The lung function tests show a significant restrictive defect. Only kyphoscoliosis or a pneumonitis may fit this picture but given the normal/high KCO (i.e. after correcting for alveolar volumes), the most likely answer is kyphoscoliosis as the gas exchange after correcting for the alveolar volume would in fact be high.
    • 86. A 35 year old lady with systemic sclerosis has breathlesness on exertion. She has bilateral basal crepitations in the chests and corresponding interstitial shadowing on the CXR. Which is likely to be found on her lung function tests? A. P02 of 11 desaturating to 10 on exertion B. FEV1 to FVC ratio of 65% C. Diffusion capacity (DLCO) of 17 (predicted 23) D. Increased residual volume E. FEV1 of 5 L
    • 87. c) diffusion capacity (DLCO) of 17 (predicted 23). A decrease in diffusion capacity (DLCO) indicates interstitial lung disease, which is likely in a patient with basal crepitations and a predisposing connective tissue disease
    • 88. A 30 year old man has kyphoscoliosis affecting his respiratory function. Which one of the following is associated? A. Inclusion body myositis B. Genital ulceration C. Klebsiella pneumonia D. Pectus excavatum E. Osteogenesis imperfecta
    • 89. Answer: e) osteogenesis imperfecta. Kyphoscoliosis occurs in : Connective tissue disorders -osteogenesis imperfecta, neurofibromatosis, Marfans Neuromuscular disorders – poliomyelitis, Duchenne’s , Friedrich’s ataxia, syringomyelia Pulmonary disorders – Unilateral fibrosis, empyema, pneumonectomy. A restrictive defect occurs due to a reduction in FVC. Hypoxia is the first consequence, later hypercapnia and cor pulmonale may occur. Pectus excavatum is an inward chest wall deformity which may be due to the pull of diaphragmatic fibres during development. It is seldom symptomatic as is pectus carinatum, which is a protrusion deformity due to skeletal overgrowth.