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Pulmonary Function Testing

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1 Pulmonary Function Testing
Danish Thameem M.D. Pulmonary and Critical Care Medicine

2 Indications for Pulmonary Functions
Evaluation of a pulmonary symptom Evaluation of smokers without symptoms Evaluation of workers exposed to hazards Quantification of impairment Evaluate response to therapy Preoperative assessment Disability evaluation

3 Timeline of cigarette smokers that develop obstructive lung disease.

4 Types of Pulmonary Function Tests
Spirometry Lung Volumes Diffusion Capacity Maximal Respiratory Pressures Maximum Voluntary Ventilation (MVV) Arterial Blood Gases Pulse Oximetry Bronchoprovocation Evaluate gas exchange – diffusion capacity and abg.

5 Lung Volumes Diagram Volume if cannot be broken down in smaller subcomponents.

6 Lung Volumes and Capacities
Four Volumes VT IRV ERV RV Four Capacities VC IC FRC TLC


8 General Approach to Interpretation
Is the test interpretable? Are the results normal? Or abnormal? What is the pattern? What is the severity? What does this mean for the patient? PFT’s cannot make a diagnosis; however, patterns can help narrow differential diagnosis.

9 Acceptability Criteria for Spirograms
Free from artifacts Cough or glottis closure during the first second of exhalation Early termination or cutoff Variable effort Leak Obstructed mouthpiece Satisfactory exhalation 6 sec of exhalation and/or a plateau in the volume-time curve or Reasonable duration or a plateau in the volume-time curve or The subject cannot or should not continue to exhale Good start Extrapolated volume is <5% of FVC or 0.15 L, whichever is greater or Time to PEF is <120 ms (optional until further information is available)

10 Repeatability Criteria
After three acceptable spirograms have been obtained, apply the following tests Are the two largest FVCs within 0.2 L of each other? Are the two largest FEV1s within 0.2 L of each other? If both of these criteria are met, the test session may be concluded. If both of these criteria are not met, continue testing until: Both of the criteria are met with analysis of additional acceptable spirograms or A total of eight tests have been performed or Save a minimum of three best maneuvers

11 Spirometry FVC (forced vital capacity): maximum volume of air that can be exhaled during a forced maneuver (after maximal forced inspiration, TLC) FEV1 (forced expired volume in one second): volume expired in the first second of maximal expiration after a maximal inspiration FEV1/FVC: FEV1 expressed as a % of FVC, a clinically useful index of airflow limitation

12 Spirogram

13 Predicting Normal Values
Depend on patient’s Height Age Gender Racial & ethnic background Weight & BMI (to a lesser degree) Reference Standards

14 Percent Predicted as Normal Range
Results are expressed as % Predicted of a predicted normal value of a person the same age, sex, and height. (FVC and FEV1) Normal Ranges FVC % FEV % FEV1/FVC >0.70 of predicted ratio

15 Obstruction vs. Restriction
If the FVC and / or FEV1 is below normal The distinction between obstruction & restriction is based on the FEV1/FVC ratio NIH/WHO - GOLD guidelines recommends using ratio below 0.70 for the diagnosis of COPD ATS – FEV1/FVC ratio 0.08 to 0.10 less than the predicted ratio.

16 Obstructive Lung Disease
Emphysema & Chronic Bronchitis Cystic Fibrosis Asthma Bronchiectasis Some Interstitial Lung Disease: (combined)

17 Restrictive Pattern Normal or elevated FEV1/FVC ratio
With a low FEV1 or FVC suggests restriction Lung Volumes are needed to confirm Some patients with Asthma or COPD may have this pattern (“pseudorestriction”)

18 Restrictive Lung Disease

19 Rating of Severity May be based on statements such as from the American Thoracic Society (ATS) Obstructive Pattern - FEV1 Restrictive Pattern – TLC (lung volumes) If lung volumes not obtained - FVC

20 ATS/ERS Standardization of Lung Function Testing:
Interpretative Strategies for lung function tests

21 Classification of COPD by Severity GOLD Guidelines - 2009
I: Mild FEV1/FVC < 70%; FEV1 > 80% predicted II: Moderate FEV1/FVC < 70%; 50% < FEV1 < 80% III: Severe FEV1/FVC < 70%; 30% < FEV1 <50% IV: Very FEV1/FVC < 70%; FEV1 < 30% predicted Severe or FEV1 < 50% predicted plus chronic respiratory failure

22 Bronchodilator Response
Must use bronchodilator with rapid onset Albuterol Levalbuterol Increase FEV1 or FVC from baseline By at least 12% By at least 200 mL Both values must be met Help differentiate between asthma and copd. If not responsive does not mean not to use bronchodilators.

23 Flow Volume Loops

24 Normal


26 Upper Airway Obstruction Patterns
Detect obstructive lesions in the major airways. Characterizes the lesion: Location of the lesion: Intrathoracic Extrathoracic Behavior of the lesion in rapid inspiration and expiration: Fixed Variable Uncommon. Suspicion based on FVL. Different from obstruction of more distal airways due to asthma and COPD.

27 Variable Extrathoracic Obstruction
Extrathoracic - above the suprasternal notch. Effects of forced expiration and inspiration in dynamic extrathoracic airway obstruction. Left, during forced expiration, intratracheal pressure (Ptr) exceeds the pressure around the airway (Patm), lessening the obstruction. Right, during forced inspiration, when intratracheal pressure falls below the atmospheric pressure, the obstruction worsens resulting in flow limitation. Vocal cord paralysis Goiter Tumor Levitzky MG Pulmonary Physiology, McGraw Hill 4th ed, 1995, p 50

28 Variable Intrathoracic Obstruction
Lesion is within the thoracic cavity – below suprasternal notch. Left panel, during forced expiration, the intrathoracic intratracheal pressure (Ptr) is less than the pressure in the pleural pressure (Ppl), worsening the obstruction. Right, during forced inspiration, intratracheal pressure exceeds the pleural pressure, lessening the degree of obstruction. Tracheomalacia Intratracheal tumor Levitzky MG Pulmonary Physiology, McGraw Hill 4th ed, 1995, p 50

29 Fixed Obstruction Tracheal stenosis/stricture
Bilateral vocal cord paralysis Extrinsic compression Levitzky MG Pulmonary Physiology, McGraw Hill 4th ed, 1995, p 50

30 Lung Volumes

31 Lung Volumes Diagram Volume if cannot be broken down in smaller subcomponents.

32 Lung Volumes in Lung Diseases

33 Diffusion Capacity Estimates the transfer of oxygen in the alveolar air to the red blood cell. Factors that influence the diffusion: 1) Area of the alveolar-capillary membrane (A) 2) Thickness of the membrane (T) 3) Driving pressure 4) Hemoglobin 5) Carboxyhemoglobin

34 Diffusing Capacity Single-breath DLCO measures the capacity of the lung to transfer gas Patient exhales to RV then rapidly inhales gas mixture with minute amount of CO. After, 10 second breath-hold at TLC, the patient rapidly exhales & the exhaled gas is analyzed to measure the amount of CO transferred into the capillary blood during the maneuver

35 Abnormalities of Diffusing Capacity
Decreased in conditions that disrupt the alveolar-capillary surface for gas transfer Loss of surface area (resection, fibrosis, emphysema, pneumonia) Reduced lung capillary volume (vasculitis, thromboembolism, primary pulm htn, ILD) Increased diffusion distance (PAP, PCP)

36 Abnormalities of Diffusing Capacity
Increased by conditions that lead to recruitment of pulmonary vascular bed and increase in capillary blood volume (exercise, mild CHF, asthma) Or by increased amount of hemoglobin which binds CO (pulmonary hemorrhage, erythrocytosis)

37 CASE 1 54 y/o male smoker PFT FEV1 : 1.3 L (23%) FVC : 2.3 L (45%)
FEV1/FVC : 56 TLC 98% RV : 156% DLCO : 30%

38 COPD Diagnosis Very severe obstructive defect Severe reduction in DLCO
High RV Air trapping COPD

39 CASE 2 35 y/o F with SLE FEV1 : (56%) FVC : (45%) FEV1/FVC 90
TLC : 48% RV: 45% DLCO : 23% FEV1 increased by 4% (0.1 L) with bronchodilator testing

40 Diagnosis Severe restriction without significant response to bronchodilators Severe reduction in DLCO ILD PULMONARY FIBROSIS

41 CASE 3 45 y/o female with history of allergic rhinitis and dyspnea on exertion FEV (70%) pre, 4.5 (100%) post BD FVC (70%) pre, 6.0 (85%) post BD RATIO - 65% pre and 75% post TLC - 6 L (100%) DLCO - 100%

42 Diagnosis Mild obstruction with significant response to bronchodilators (normal) Normal lung volumes and DLCO ASTHMA

43 CASE 4 76 y/o male with weight loss and dyspnea FEV1 - 4 L ( 85%)
FVC L (80%) RATIO - 78% TLC - 6 L ( 82%) DLCO - 88%

44 Diagnosis EXTRATHORACIC OBSTRUCTION Normal spirometry
Truncated inspiratory limb of the flow volume loop EXTRATHORACIC OBSTRUCTION








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