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Pulmonary Physiology and Lung Function Tests

Pulmonary Physiology and Lung Function Tests. Conor O’Dochartaigh FRACP Teaching 24/10/07. Lung Function Testing (PFTs). Spirometry (FV loop spirometry, dynamic lung volumes) Reversibility testing Bronchial challenge testing Static lung volumes (TLC, FRC)

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Pulmonary Physiology and Lung Function Tests

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  1. Pulmonary Physiology and Lung Function Tests Conor O’Dochartaigh FRACP Teaching 24/10/07

  2. Lung Function Testing (PFTs) • Spirometry (FV loop spirometry, dynamic lung volumes) • Reversibility testing • Bronchial challenge testing • Static lung volumes (TLC, FRC) • Gas Transfer (DLCO, TLCO Transfer factor, KCO, ) • Maximal respiratory pressures (Mouth pressures) • CPEST (Cardiopulmonary exercise test)

  3. General principles • Technical factors • operator • patient • within test repeatability • confounding factors • Quality control – between test repeatability • Appropriate reference values

  4. Spirometry • Measures the ability to move air rapidly • Depends on nervous system, musc skel, skin + connective tissue, lungs, airways, inhaled gas

  5. How is the test done • Apparatus • true spirometers - volume & time • pneumotach, vane & hotwire anenometers - flow • Method • Full inspiration, forced maximal expiration • Minimum 3 technically acceptable attempts • within 5% repeatability FEV1 and FVC • Slow Vital Capacity may also be checked

  6. Data generated • Volume time curve (spirogram) • FEV1, FVC, Ratio • Flow volume loop • Peak flow • FVC • FEF 25-75% • MEF 75, 50, and 25 • Inspiratory flow data

  7. NORMAL

  8. Spirometry interpretation • Obstructive v. Restrictive • Mid flow obstruction • Shape of the FV loop • Obstruction v. restriction • Fixed large airway obstruction • Variable airway obstruction • Extrathoracic • Intrathoracic

  9. Airflow obstruction Mild on left Severe on right

  10. Classification of COPD Severity by Spirometry Stage I: Mild FEV1/FVC < 0.70 FEV1> 80% predicted Stage II: Moderate FEV1/FVC < 0.70 50% < FEV1 < 80% predicted Stage III: Severe FEV1/FVC < 0.70 30% < FEV1 < 50% predicted Stage IV: Very Severe FEV1/FVC < 0.70 FEV1 < 30% predicted or FEV1 < 50% predicted plus chronic respiratory failure

  11. True or False • Spirometry showing FEV1 < 80% of predicted and FEV1/FVC ratio <70% is diagnostic of COPD

  12. ID: CSM4166 Date: 10/03/04 Gender: Male Age: 62 Weight(kg): 79.0 Height(cm): 184 BMI: 23.33 PB: 753 Temp: 23 Pre Pre Post Post Post Ref Meas % Ref Meas % Ref % Chg 4.86 4.48 92 3.38 (1.61) (48) 70.0 (36.0) 3.11 (0.35) (11) 9.02 5.43 60 Spirometry FVC FEV1 FEV1/FVC FEF25-75% PEF Lung Volumes TLC RV RV/TLC FRC PL ERV VC Resistance Raw sRaw Diffusion DLCO DLCO /VA VA COPD Comments:The patient could not fully expire during to FVC or SVC, therefore the results for both vital capacities may be underestimated. See attached FV loops

  13. Pulmonary restriction

  14. ID: HLJ7135 Date: 04/08/04 Gender: Female Age: 83 Weight(kg): 61.0 Height(cm): 162 BMI: 23.24 PB: 753 Temp: 22 Scleroderma Pre Pre Post Post Post Ref Meas % Ref Meas % Ref % Chg 2.52 (1.58) (63) 1.69 1.13 67 69.0 71.0 1.90 0.71 37 5.15 4.92 96 Spirometry FVC FEV1 FEV1/FVC FEF25-75% PEF Comments: Acceptable and repeatable results obtained. Interpretation:

  15. True or False? • A spirometry showing an FEV1< 80% of predicted, FVC < 80% of predicted and FEV1/FVC ratio of >70% is diagnostic of Pulmonary Restriction.

  16. Large Airway obstruction • Tracheal • Fixed obstruction – expiratory and inspiratory limitation • Variable obstruction • Inspiratory limitation indicates extrathoracic obstruction • Expiratory limitation indictaes intrathoracic obstruction

  17. Variable extrathoracicFixed Large airway obstruction

  18. ID: CLV3379 Date: 22/03/01 Gender : Male Age: 30 Weight(kg): 82.0 Height(cm): 171 BMI: 28.04 PB: 765 Temp: 25 Pre Pre Post Post Post Ref Meas % Ref Meas % Ref % Chg 4.93 5.48 111 3.94 3.45 88 79 (63) 4.31 3.26 76 8.95 (3.83) (43) Spirometry FVC FEV1 FEV1/FVC FEF25-75% PEF Lung Volumes TLC RV RV/TLC FRC PL ERV VC Resistance Raw sRaw Diffusion DLCO DLCO /VA VA Fixed Extrathoracic Obstruction PFT Comments: All tests were done well with good patient effort and technique and results were acceptable and reproducible. Interpretation: Spirometry suggests obstructive pattern but flow loop consistent with fixed extrathoracic obstruction. Lung volumes and gas transfer preserved, making bleomycin lung disease unlikely. Does this subject have tracheal narrowing or an enlargedthyroid?.

  19. Reversibility • How? • Off inhalers • Spiro • Inhaled bronchodilator • Check spiro again • Data • Absolute and %predicted pre&post FEV1 & FVC

  20. Interpretation • Definition of significant response • FEV1 inc. by 15% AND 200ml • FEV1 or FVC inc. by 12% AND 200ml • What does reversibility mean? • Reversible airflow obstruction • Asthma • COPD with reversibility • COPD + asthma

  21. ID: AKC1991 Date: 21/06/04 Gender: Male Age: 40 Weight(kg): 96.0 Height(cm): 189 BMI: 26.87 PB: 745 Temp: 21 Pre Pre Post Post Post Ref Meas % Ref Meas % Ref % Chg 5.71 6.05 106 6.31 110 4 4.27 3.74 88 4.27 100 14 74.0 62.0 68 4.19 (1.99) (47) 2.66 63 33 10.27 10.19 99 9.4 91 -8 Spirometry FVC FEV1 FEV1/FVC FEF25-75% PEF Lung Volumes TLC RV RV/TLC FRC PL ERV VC Resistance Raw sRaw Diffusion DLCO DLCO /VA VA Bronchodilator Response PFT Comments: Acceptable and repeatable results obtained. Ventolin (2.5gm) was administered for bronchodilator testing. Interpretation:

  22. ID: AQA1519 Date: 16/08/04 Gender Female : Age: 63 Weight(kg): 47.0 Height(cm): 153 BMI: 20.08 PB: 734 Temp: 22 Pre Pre Post Post Post Ref Meas % Ref Meas % Ref % Chg 2.54 1.83 72 2.66 105 45 1.83 (0.76) (41) 1.17 64 54 73.0 (41.0) (44.0) 2.26 (0.25) (11) (0.35) (15.0) 41 5.15 2.36 46 3.64 71 54 Spirometry FVC FEV1 FEV1/FVC FEF25-75% PEF Lung Volumes TLC RV RV/TLC FRC PL ERV VC Resistance Raw sRaw Diffusion DLCO DLCO /VA VA Bronchodilator ResponsePFT Comments: Acceptable and repeatable results obtained. 2.5 mg of Ventolin was administered for 2 mins for bronchodilator testing. Interpretation: Clinical details provided: COPD, ex smoker ? reversibility. Spirometric lung volumes are indicative of a very significant degree of airflow limitation with more profound flow limitation at mid and low lung volumes. There is however a clinically important bronchodilator response.

  23. Bronchial challenge testing - • Often used for asthma diagnosis • How? • Off inhalers • Check spirometry • Inhale a bronchoprovocator (histamine, methacholine, saline) at inc. concentrations • measure spirometry after each inhalation • N.B. exercise as a bronchoprovocator

  24. Bronchial challenge testing - Data • PD20 = ‘Provocative Dose’ required to produce a 20% drop in FEV1 • Histamine + if <4micromol • PC20 = ‘Provocative Concentration’ required to produce a 20% drop in FEV1 • Histamine + if <8mg/ml • PC20/PD20 also used for Methacholine • Hypertonic saline

  25. ID: NDZ2751 Date: 16/12/03 Gender: Male Age : 31 Weight(kg): 81.5 Height(cm): 182 BMI: 24.60 PB: 7510 Temp: 23 Histamine Dose Response HistaminePre 1 2 3 4 5 6 7 8 9 Post Post ResponseMeas % % % % % % % % % Meas % FVC 6.48 -3 -2 -4 -14 6.30 -3 FEV1 4.82 -6 -8 -14 -29 5.02 2 FEV1/FVC 74 80 FEF25-75% 3.86 -9 -16 -31 -45 4.62 20 PEF9.88 -11 -15 -19 -3110.03 1 Comments: Acceptable and repeatable results obtained. Histamine baseline Spirometry trials 5,6,7. Histamine test was positive with PD20 =0.419. Ventolin (2.5 mg) was administered to release bronchoconstriction caused during bronchoprovocation challenge. Interpretation: Baseline spirometry, static lung volumes and transfer factor are within normal limits. Bronchial challenge testing shows bronchoconstriction/airways hypersensitivity which is consistent with asthma in the appropriate clinical context.

  26. Bronchial challenge - interpretation • Threshold for positive may vary centre to centre • Indicates ‘Bronchial hyperresponsiveness’ • Negative test virtually excludes asthma • False positives post-infection

  27. Static lung volumes • Why? • Measure residual volume (and therefore TLC) • How? • Measure the FRC • Plethysmography or Gas dilution • Plethysmography (bodybox) preferred • measures poorly ventilated airspaces • 2 types - volume-displacement & volume-constant

  28. Lung volumes

  29. Volume-constant body plethysmograph

  30. Lung volumes - interpretation • True restriction - reduced TLC • Hyperinflation - high TLC • Gas trapping - High RV, RV/TLC ratio • Neuromuscular disease -  TLC, preserved or raised RV

  31. ID: BDD9943 Date: 23/06/04 Gender: Male Age: 55 Weight(kg): 65.0 Height(cm): 168 Race: BMI: 23.03 PB: 754 Temp: 21 Pre Pre Post Post Post Ref Meas % Ref Meas % Ref % Chg 4.2 (2.0) (48.0) 3.1 (.8) (25.0) 73.0 (37.0) 3.1 (.3) (10.0) 7.8 (2.6) (33.0) 5.8 (9.3) (162.0) 2.0 (7.0) (346.0) 36.0 (75.0) 3.4 (7.1) (211.0) 1.4 (.3) (19.0) 4.2 (2.4) (57.0) 1.4 7.0 518.0 4.6 56.6 1243.0 20.6 14.7 71.0 4.0 3.1 78.0 6.3 (4.8) (75.0) Spirometry FVC FEV1 FEV1/FVC FEF25-75% PEF Lung Volumes TLC RV RV/TLC FRC PL ERV VC Resistance Raw sRaw Diffusion DLCO DLCO /VA VA COPD PFT Comments: The patient could not fully expire during forced and slow expiration, therefore the results were not quite accurate, even though they were repeatable. Interpretation: Stable lung function.

  32. True or False • Transfer factor is a specific measure of gas transfer at the alveolo-capillary membrane

  33. Transfer factor • Gas exchange by the lung depends on: • Ventilation of the airways and some air spaces by bulk flow of gas; • Mixing and diffusion of gases in the alveolar ducts, air sacs and alveoli; • Transfer of gases across the gaseous to liquid interface of the alveolar membrane; • Mixing and diffusion in the lung parenchyma and alveolar capillary plasma; • Chemical reaction with constituents of blood; • Circulation of blood between the pulmonary and systemic vascular beds.

  34. Transfer factor – How? • Inhale to TLC a gas mix containing known concentrations of CO & He • Hold breath 10 sec • Exhale • Discard dead space • Collect ‘alveolar’ gas • Use He dilution to calculate VA & starting Alveolar CO

  35. DLCO – Data generated • Then DLCO is calculated from the difference between ‘starting’ CO conc., and CO conc. after 10 sec in contact with alveoli • Expressed in ml/mmHg/min • VA = TLC by single breath helium dilution • DLCO/VA = transfer coefficient (KCO)

  36. DLCO - interpretation • DLCO↓ by: • Pulmonary vascular diseases • Conditions affecting alveoli • Cardiac diseases • Anaemia • Pregnancy • Recent smoking

  37. DLCO - interpretation • DLCO↑ by • Polycythaemia • Pulmonary haemorrhage • L to R shunt • Exercise • KCO (DLCO/VA) • Corrected for volume. Theoretical function of the individual alveolus (??)

  38. ID: BDD9943 Date: 23/06/04 Gender: Male Age: 55 Weight(kg): 65.0 Height(cm): 168 Race: BMI: 23.03 PB: 754 Temp: 21 Pre Pre Post Post Post Ref Meas % Ref Meas % Ref % Chg 4.2 (2.0) (48.0) 3.1 (.8) (25.0) 73.0 (37.0) 3.1 (.3) (10.0) 7.8 (2.6) (33.0) 5.8 (9.3) (162.0) 2.0 (7.0) (346.0) 36.0 (75.0) 3.4 (7.1) (211.0) 1.4 (.3) (19.0) 4.2 (2.4) (57.0) 1.4 7.0 518.0 4.6 56.6 1243.0 20.6 14.7 71.0 4.0 3.1 78.0 6.3 (4.8) (75.0) Spirometry FVC FEV1 FEV1/FVC FEF25-75% PEF Lung Volumes TLC RV RV/TLC FRC PL ERV VC Resistance Raw sRaw Diffusion DLCO DLCO /VA VA COPD PFT Comments: The patient could not fully expire during forced and slow expiration, therefore the results were not quite accurate, even though they were repeatable. Interpretation: Stable lung function.

  39. ID: ALE6999 Date:11/05/04 Gender: Female Age: 63 Weight(kg): 81.0 Height(cm): 169 BMI: 28.36 PB: 767 Temp: 23 Pre Pre Post Post Post Ref Meas % Ref Meas % Ref % Chg 3.34 2.89 87 2.46 2.21 90 73.0 76.0 2.68 1.87 70 6.02 4.75 79 5.47 5.63 103 2.11 2.58 122 38.0 46.0 2.90 2.79 96 1.12 (0.31) (27) 3.34 3.05 91 1.31 2.09 159 3.80 7.46 196 23.3 (9.80) (42.00) 3.82 2.1 55 4.66 Spirometry FVC FEV1 FEV1/FVC FEF25-75% PEF Lung Volumes TLC RV RV/TLC FRC PL ERV VC Resistance Raw sRaw Diffusion DLCO DLCO /VA VA Sclerorderma PFT Comments: Acceptable and repeatable results obtained. Interpretation: No significant change since Nov 2001.

  40. 59 yo female smoker, BMI = 24

  41. Other patterns • Obesity • Restrictive Spirometry and TLC, very reduced FRC, reduced RV. DLCO only reduced in very gross obesity • Heart Failure • Obstructive in Acute, Restrictive in Chronic with decreased gas transfer • Neuromuscular • Decreased FVC, lower when supine, decreased TLC, preserved RV, preserved DLCO

  42. Other tests to be aware of • Airways resistance (RAW) and conductance • In the plethysmograph • Impulse oscillometry • Effort independent • Can identify site of obstruction • Maximal Inspiratory and Expiratory pressures • Mouth pressures • Musculoskeletal disorders

  43. Q1 • Which of the following spirometric parameters is thought to represent the least effort-dependent part of the expiratory flow volume loop • Peak expiratory flow (PEFR) • Forced Vital capacity • Forced expiratory volume in one second (FEV1) • FEV1/FVC ratio • Mid expiratory flow (FEF25-75%), aka Forced expiratory flow between 25% and 75% of FVC

  44. Q2 • Preoperative lung function testing in a 55 year old man with COPD shows a Forced Vital Capacity (FVC) of 2.0L (48% of predicted), and a Total Lung capacity (TLC, measured by body plethysmography) of 9.3 L (162%). Three months following lung volume reduction surgery, what pattern of change can be expected in these parameters? • No change • FVC and TLC are both increased • FVC and TLC are both decreased • FVC is increased and TLC is decreased • FVC is decreased and TLC is increased

  45. Q3 (2003) A 66-year-old man presents with progressive exertional dyspnoea. His anthropometric indices are: Hieght 175 cm Weight 98 kg Body Mass Index (BMI) 32 kg/m2 [18-25] His lung function test results are: Forced expiratory volume in one second (FEV1) 1.72L (56% predicted) Forced vital capacity (FVC) 2.14L (54% predicted) FEV1/FVC 80% Total Lung Capacity (TLC) 4.12 L (64% predicted) Residual Volume (RV) 1.98L (84% predicted) Diffusing capacity for carbon monoxide Corrected for volume (KCO) 4.9 ml/min/mmHg/L (110% predicted)

  46. Q3 contd What is the most likely cause of this man’s dyspnoea and lung function abnormalities? • Obesity • Pulmonary fibrosis • Chronic obstructive pulmonary disease • Cardiac failure • Bilateral diaphragm paralysis

  47. Q4 • Disproportionately preserved peak expiratory flow in Pulmonary fibrosis is due to which of the following mechanisms • Increased pulmonary elastic recoil • Decreased pulmonary elastic recoil • Increased airways resistance • Decreased airways resistance • Impaired gas exchange

  48. Q5 • Which of the following apparatus used for flow-volume spirometry does not extrapolate volume from flow? • Vane anemometer • Hot wire anemometer • Pneumotachnograph • Water seal spirometer

  49. Q6 • This flow-volume loop was produced by a patient with a history of Wegener’s Granulomatosis.

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