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- 1. Pulmonary Function Testing Training Module Presenter : Dr. Siddharth Jain Moderator: Dr. Mitul Jain Preceptor: Dr. Vignesh MantharamDate: 27/06/2015 Under the able guidance of Prof. S.K. Sharma and Dr. Ragesh R. Nair
- 2. Learning objectives At the end of this training program, the residents should : • Understand the basics of pulmonary functions • Be aware of pretest evaluation • Have a clear understanding about the various maneuvers • Become adept at interpreting pulmonary function testing
- 3. Preview • History • Indications • Pre‐test evaluation • Lung volumes and capacities • Pulmonary function tests • Performing a PFT • Interpretation of PFT • Case vignette • Quiz
- 4. History of Pulmonary Function Testing • 1846 Hutchinson – Spirometer • 1979 ATS standardization of PFT • 2002 ATS statement on 6‐minute walk test • 2003 ATS/ACCP statement on cardiopulmonary exercise testing • 2005 ATS/ERS Task Force: General considerations, spirometry, diffusion capacity, lung volumes and interpretation • 2014 ATS/ERS Technical Standards: Field walking tests in chronic respiratory disease 4 ATS: American Thoracic Society ERS: European Respiratory Society ACCP: American College for Chest Physicians PFT Pulmonary Function Testing
- 5. Indications of Pulmonary Function Testing • Diagnosis of a respiratory disease • Assessment of disease activity • Monitoring response to therapy • Assessment of disability • Evaluation of prognosis • Pre‐operative assessment
- 6. • Name • Age • Sex • Ethnicity • Height • Clinical diagnosis • Smoking • Alcohol • Drugs Pretest Evaluation
- 7. Pretest evaluation For reversibility and provocation test, if feasible, avoid the following drugs for a specified duration prior to the study: • SABA inhaler 12 hours • SAMA inhaler 24 hours • Leukotriene Response modifiers 24 hours • LABA inhaler 48 hours • Theophyllines 48 hours • Anti‐ Histaminic agents 72 hours SAMA = Short acting muscarinic antagonist SABA = Short acting beta agonist LABA = Long acting beta agonist LAMA = Long acting muscarinic antagonist
- 8. Pretest Evaluation • Active pulmonary infection • Hemodynamic instability • Myocardial infarction within past 1 month • Ocular or Cardiothoracic surgery within past1 ½ years • Impaired mental state • Chest or abdominal pain • Oral ulcers and facial pain
- 9. Advise prior to PFT • Patient is given an appointment • To come in loose clothes that will allow full chest and abdominal expansion • No caffeine based drinks on the day of the study • No alcohol 4 hours prior • No large meal 2 hours prior • No smoking 1 hour prior • No vigorous exercise 30 min prior
- 11. Tidal volume Vital capacit y Expiratory Reserve Volume Residual Volume Functional Residual Capacity Inspiratory Reserve Volume Total Lung capacit y Lung volumes and capacities Inspiratory capacity Expiratory capacity t(s)
- 12. Factors influencing lung functions • Age • Sex • Height • Ethnicity • Posture • Respiratory muscle strength • Technique • Disease states
- 13. Bedside Pulmonary Function assessment • Breath holding Test – Breath hold up to 25 seconds indicate adequate cardiopulmonary reserve • Single breath count – A healthy adult can count to 30‐40 in a single breath • Cough after deep breath • Candle blowing test
- 14. • A measure of maximum breathing capacity • Patient is asked to blow an illuminated candle from a distance of 6 inches with wide open mouth, chin rested, without head movement • Blowing a candle at 6” indicates a maximum breathing capacity of > 60 L/min and FEV1 of >1.6 L Candle blowing test FEV1:Forced Expiratory Volume at the first second of expiration
- 15. List of Pulmonary Function Tests Spirometry SVC maneuver FVC maneuver Maximum Voluntary Ventilation Maximal Respiratory Pressures Tests of Absolute Lung Volume measurements Body Plethysmography Nitrogen wash‐out method Helium dilution method Tests of gas exchange Diffusion Lung Capacity of Carbon Monoxide Tests of cardiopulmonary interaction 6‐minute walk test Cardio‐Pulmonary Exercise Testing SVC = Slow vital capacity FVC = Forced vital capacity
- 17. A good manoeuvre • Acceptibility criteria • No. of attempts • Time gap between each attempts • Repeatabilty criteria
- 18. Acceptable SVC curve IC EV C IC‐ Inspiratory capacity
- 19. Curve selection • Maximum no. of attempts: 4 • Time between each attempt: 1 minute • Minimum no. of acceptable curves: 3 • Repeatability criteria: – Differences in vital capacity not >150 mL between the two manoeuvres with largest values . • Maximum value is reported as the slow vital capacity • Mean value is taken for reporting inspiratory capacity.
- 20. Interpreting an SVC manoeuvre Attempt no. Expiratory Vital Capacity (L) Inspiratory capacity ( L) 1 4.32 3.01 2 4.42 3.05 3 4.37 2.97 ‐ Mean IC : 3.01 Slow vital capacity is: 4.42 L (86% predicted, >LLN) Inspiratory capacity : 3.01 L ( No reference equation) LLN: Lower limit of normal
- 23. Acceptable volumetime curve • Good start No artifacts hesitation cough sub‐maximal effort air leak obstructed mouthpiece • Satisfactory exhalation Duration of exhalation > 6s or Plateau in the volume time curve >1 s No artifacts Early termination Glottic closure
- 24. Flow volume loop
- 26. Curve selection Attempt no. FVC (L) FEV1 (L) FEV1 + FVC(L) 1 4.68 3.85 8.53 2 4.65 3.64 8.29 3 4.63 3.78 8.41 • Maximum no. of attempts: 8 • Time between each attempt: 1 minute • Minimum no. of acceptable curves: 3 • Repeatability criteria: The two largest values of FVC must be within 150 mL of each other The two largest values of FEV1 must be within 150 mL of each other • Curve with maximum sum of both FEV1 and FVC is taken as the best curve for interpretation.
- 27. Concept of obstruction and restriction Respiratory disease Obstruction Restriction Basic pathology Airway obstruction Parenchymal or extra parenchymal damage restricting the chest wall expansion Functional defect Increased airway resistance Reduced compliance Forced Vital capacity Normal May be declined in severe obstruction Reduced May be normal in early stages of restriction Slow vital capacity Normal even in severe stages (Dynamic airway narrowing) Reduced e.g. Chronic obstructive airway disease Bronchial Asthma Interstitial Lung Disease Morbid Obesity Kyphoscoliosis
- 28. Variables assessed in FVC and SVC maneuver Parameters Utility in disease states FEV1 Forced expiratory volume in the first second Obstruction FVC Forced vital capacity Restriction Severe obstruction SVC (EVC/IVC) Slow Vital Capacity (Expiratory /Inspiratory Vital Capacity) Restriction FEV1/FVC Ratio of FEV1 to FVC Obstruction PEFR Peak expiratory flow rate Obstruction PEF25‐75 Peak expiratory flow from 25% to 75% of expiration Small airway disease Normal variant MEF50 Maximum expiratory flow at mid expiration Variable intra‐thoracic / Fixed intra‐thoracic obstruction MIF50 Maximum inspiratory flow at mid inspiration Variable extra‐thoracic Fixed intra‐thoracic obstruction
- 29. Obstruction and Restriction in Flow Volume Loop Normal Obstruction Restriction
- 30. Interpreting FVC/SVC manoeuvre FEV 1/VC VC Possible restrictio n Normal V C Severe Obstruction/ Obstruction with possible restriction. Obstruction Normal Normal VC manoeuvre Normal Reduce d Reduced* Reduced* *Reduced infers that the variable is < LLN VC = Vital Capacity, FEV1 Forced Expiratory Volume at the first second
- 34. Severity of obstruction Severity of obstruction FEV1% predicted ( ATS/ERS) Mild >70 Moderate 60 ‐ 69 Moderately severe 50 – 59 Severe 35 – 49 Very severe <35 Severity of obstruction FEV1% predicted ( GOLD) Mild 80+ Moderate 50 ‐ 79 Severe 30 – 49 Very severe <30 ATS = American thoracic society ERS = European Respiratory Society GOLD = Global initiative against Obstructive Lung Disease
- 35. Upper airway obstruction Extra‐thoracic airway Intra‐thoracic airway obstruction obstruction
- 36. Upper airway obstruction Variable Intra thoracic Obstruction Variable Extra thoracic Obstruction Fixed Extra thoracic Obstruction Pathology Defective Expiration Defective Inspiration Defective inspiration and expiration PEF Decreased Normal Decreased MIF50/MEF50 >1 <1 1 e.g. Bronchial adenoma Vocal cord palsy Tracheal stenosis
- 37. Bronchoprovocative testing History suggestive of asthma with normal spirometry and no reversibility Episodic chest tightness with cough but no wheezing Chronic cough which is often worse at night but without wheezing Unexplained dyspnea Recurrent episodes of cold, bronchitis or recurrent pneumonia which does not occur in the same lung region. Used in the detection of hyperactive airways if :
- 40. Acceptable MVV curve • Minimum no. of breaths in 12 seconds: 19 • Amplitude of breaths > 50% of vital capacity
- 41. • Maximum no. of attempts : no recommendation • Time between each attempts: no recommendation • Minimum no. of acceptable curves: 2 • Repeatability criteria: MVV between the curves do not differ by more than 20% • Curve with largest MVV is selected for reporting • MVV/ FEV1 > 0.32 indicates good effort and normal respiratory muscle strength • Has high negative predictive value. Normal MVV goes against the presence of muscle weakness. Curve selection Attempt no. MVV(L/min) LLN Predicted % predicted 1 139.5 115.4 145.5 96 2 126.4 115.4 145.5 86 MVV‐ Maximum Voluntary attempts FEV1 Forced Expiratory Volume at 1st second LLN – Lower limit of normal
- 42. Maximal Respiratory Pressures Inspiratory / Expiratory
- 44. • Used to assess respiratory muscle strength • MIP – a function of diaphragm and other inspiratory muscles. • MEP – a function of expiratory muscles • Isolated decline in MIP indicates diaphragmatic dysfunction • Isolated decline in MEP is rare. • Decrease in both MIP and MEP indicates either a generalized muscle weakness or poor effort. Utility of maximal respiratory pressures MIP ‐Maximum inspiratory Pressure MEP ‐ Maximum Expiratory Pressure
- 45. Tests of absolute lung volume measurement
- 46. Absolute lung Volumes • Measurement of total lung capacity • Spirometer cannot measure any capacity that include residual volume(RV). • Functional residual capacity(FRC) and total lung capacity(TLC) are such capacities. – FRC = RV + ERV – TLC = FRC + IC • Inspiratory capacity(IC) from SVC maneuver • FRC from any of the lung volume assessment methods.
- 47. Absolute lung volumes • Techniques to measure the total lung capacity – Body Plethysmography – N2 washout method – Inert gas dilution method – Radiological techniques
- 48. • Raw = Alveolar driving pressure ‐ mouth pressure Flow rate • Specific airway resistance(sRaw) is airway resistance corrected for lung volumes. • Raw: elevated in both obstructive lung diseases and states of hyperinflation • sRaw elevated only in obstructive lung diseases. Airway resistance
- 51. Body plethysmography • Maximum no. of attempts: No recommendation • Time between each attempt : 1 minute • Minimum no. of acceptable curves: 3 • Repeatability criteria Highest FRCpleth – Lowest FRCpleth < 0.05 mean FRCpleth • Mean FRC is finally reported • Add IC to FRC to generate the TLC FRCpleth – Functional Residual Capacity as measured by plethysmography
- 52. Interpretation of body plethysmography Attempt no. FRCpleth(L) 1 2.78 2 2.80 3 2.67 • Mean FRC = 2.725 L • Repeatability criteria Highest FRCpleth – Lowest FRCpleth = 0.04 which is < 0.05 mean FRCpleth • Mean IC derived from SVC manouvre = 3.01 L • TLC = 2.725 + 3.01= 5.735 L (>LLN, 81% predicted)
- 53. Interpretation of TLC TL C Normal RestrictionPossible hyperinflation Reduced*Increased* *Reduced infers that the variable is < LLN *Increased infers the variable is > LLN
- 54. Diffusion Lung Capacity for Carbon Monoxide
- 55. Diffusion capacity contd… • Choice of gas for measuring DL : Readily available Easily measurable Transfer should be diffusion limited • O2 and N2O exhibit perfusion limited transfer and hence under estimate the DL • CO exhibits diffusion limited transfer and hence is the ideal gas to measure DL DL ‐ Diffusing capacity of the lungs CO – Carbon monoxide
- 56. Diffusion of CO across the alveolar wall Pulmonary Surfactant Alveolar Epithelium Alveolar Interstitium Capillary Endothelium Plasma Red Blood Cell Hemoglobin
- 57. Indications 1. Severity assessment in restrictive lung disease 2. Diagnosis of pulmonary vascular disease 3. Differentiation of parenchymal and extra parenchymal restriction. 4. Diagnosis of early ILD in high risk patients (eg; chronic amiodarone use, history of chest radiation, stage 1 sarcoidosis) ILD = Interstitial lung disease;
- 58. Physiologic variation Parameters DLCO Age Decreases with age Gender Low in females Weight High in obese Ethnicity Low in African Americans Hb concentration Low in anemia CO Hb Low in smokers Postural High in supine State of activity Increases with exertion Diurnal High in the morning Menstrual Highest on day prior to menses Lowest on D5 of menses Hb -
- 59. Diffusing capacity contd… • Five methods: 1.Single‐breath method 2.Steady‐state method 3.Re‐breathing method 4.Three‐Gas Iteration method 5.Intra‐breath method • Of these the single‐breath method is the best standardized and most validated.
- 60. DLCO by single breath
- 61. Acceptable DLCO curve • Use of proper quality‐controlled equipment • IV of 85% of largest VC in <4s • A stable calculated breath hold for 10 seconds. • No cough, leak, Muller’s , Valsalva manoeuvre • Expiration in <4 seconds • Sample collection time< 3 seconds • Washout volume 750‐1000mL • Sample volume 500‐1000mL IV ‐ Inspiratory volume VC – Vital capacity 85% VC
- 62. • Maximum no. of attempts : 5 • Time between each attempts: 4 minutes • Minimum no. of acceptable curves: 2 • Repeatability criteria: Difference in DLCO not more than 3mL CO (STPD)/min/mmHg or 10% • Mean DLCO of the two acceptable manouevers corrected for Hb and COHb is considered for interpretation. DLCO contd.. Attempt no. DLCO ml/min/mmHg LLN Predicted % predicted 1 28.43 27.16 33.96 83 2 30.54 27.16 33.96 90 Mean 29.49 27.16 33.96 86
- 63. Recap of FVC manouever FEV1/VC VC Possible restrictio n Normal V C Obstruction with Possible co‐existent restriction. Obstruction Normal Normal VC manoeuvre Normal Reduce d Reduced* Reduced* *Reduced infers that the variable is < LLN *Increased infers the variable is > LLN
- 64. Recap of TLC TL C Normal RestrictionPossible hyperinflation Reduced*Increased* *Reduced infers that the variable is < LLN *Increased infers the variable is > LLN
- 65. Interpreting DLCO in restriction DLC O Normal Extra parenchymal restriction Normal DLCO/ Va Extra parenchymal Restriction Like kyphoscoliosis Increased* Reduced* *Reduced infers that the variable is < LLN *Increased infers the variable is > LLN Va‐alveolar volume Decreased* Coexistent Pulmonary hypertension Increased* Obesity Parenchyma l restriction
- 66. Assessment of severity of restriction Severity DLCO %Predicted Mild >60% ‐ < LLN Moderate 40‐60% Severe < 40%
- 67. Interpretation of DLCO.. Miscellaneous Diseases DLCO Respiratory muscle weakness Low Isolated Pulmonary vascular disease Low Emphysema Low Early ILD Low Chronic bronchitis High Bronchial asthma High Left to Right shunts High Diffuse Alveolar hemorrhage High
- 68. Preoperative evaluation in lung resection • Post operative predicted FEV1 and DLCO used to assess the feasibility of lobar or segmental resections. • Calculated as: Predicted post‐operative(PPO) FEV1 = pre operative FEV1(1‐ y/z) Predicted post operative(PPO) DLCO = pre operative DLCO(1‐y/z) y= number of lung segments to be removed. z= total number of functional segments. PPO FEV1 and DLCO % predicted Plan >60 Surgery 30 – 60 6‐minute walk test < 30 Cardio pulmonary exercise test Chest 2013;143(5)(Suppl): e166s190s
- 69. Evaluation of the need for inflight O2 requirement Resting SpO2 > 95% < 95%92‐95% No indication for in‐flight O2 requirement Indication for in‐flight O2 requirement Risk factor for in‐flight hypoxemia • FEV1 < 50% predicted • Reduced DLCO • 6‐min walk distance <50m • AE‐COAD within 6 weeks • Restrictive lung disease • Pulmonary hypertension
- 70. Conclusion • PFT is widely underutilised and has a wider scope • Pre‐test evaluation should be given importance prior to pulmonary function testing • Patient’s performance is directly proportional to the pre‐test counselling • Always assess test performance prior to interpreting results • PFT graphics are as important as absolute values • Always interpret results with clinical context in mind
- 71. Thank you