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Pulmonary Function Testing The Basics of Interpretation

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Title: Pulmonary Function Testing The Basics of Interpretation


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2
Mohammad Tohidi M.D. Professor of Internal
Medicine Department of Pulmonary Medicine Ghaem
Hospital MUMS Mashhad IRAN
3
PFTs
4
Objectives
  • Identify the components of PFTs
  • Describe the indications
  • Develop a stepwise approach to interpretation
  • Recognize common patterns
  • Apply this information to patient care

5
Pulmonary function tests (PFTs)
  • Pulmonary function testing is a valuable tool for
    evaluating the respiratory system
  • comparing the measured values for pulmonary
    function tests obtained on a patient at any
    particular point with normal values derived from
    population studies.
  • The percentage of predicted normal is used to
    grade the severity of the abnormality.

6
Pulmonary Function Tests
  • Evaluates 1 or more major aspects of the
    respiratory system

7
PFTs
  • Four lung components include
    The airways (large and small),
    Lung parenchyma (alveoli, interstitium),
    Pulmonary vasculature, and
    The bellows-pump mechanism

8
PFTs
  • PFTs can include simple screening spirometry,
    Flow Volume Loop
  • Formal lung volume measurement,
    Bronchoprovocation testing
  • Diffusing capacity for carbon monoxide,
    and Arterial blood gases. Measurement of
    maximal respiratory pressures
  • These studies may collectively be referred to as
    a complete pulmonary function survey.

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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

11
Importance
  • Patients and physicians have inaccurate
    perceptions of severity of airflow obstruction
    and/or severity of lung disease by physical exam
  • Provides objective evidence in identifying
    patterns of disease

12
Spirometry
  • Simple, office-based
  • 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)

13
Spirometry
  • the most readily available
  • most useful pulmonary function test
  • It takes ten to 15 minutes
  • carries no risk

14
Spirometry
  • Spirometry is the most commonly used lung
    function screening study.
  • should be the clinician's first option
  • other studies being reserved for specific
    indications
  • easily performed
  • in the ambulatory setting, physician's office,
    emergency department, or inpatient setting.

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Patient care/preparations
  • Two choices are available with respect to
    bronchodilator and medication use prior to
    testing. Patients may withhold oral and inhaled
    bronchodilators to establish baseline lung
    function and evaluate maximum bronchodilator
    response, or they may continue taking medication
    as prescribed. If medications are withheld, a
    risk of exacerbation of bronchial spasm exists.

17
Spirometry
  • The slow vital capacity (SVC) can also be
    measured with spirometers
  • collect data for at least 30 seconds
  • when airways obstruction is present, the
    forced vital capacity (FVC) is reduced and
  • slow vital capacity (SVC) may be normal

18
Spirometry
  • When the slow or forced vital capacity is within
    the normal range
    No significant restrictive
    disorder .
  • No need to measure static lung volumes
    (residual volume and total lung capacity).

19
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

20
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

Smokers gt 45yo (former current)
21
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

22
Indications Prognostic
  • Assess severity
  • Follow response to therapy
  • Determine further treatment goals
  • Referral for surgery
  • Disability

23
Contraindications for spirometry
  • Relative contraindications for spirometry include
    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, and patients with a history
    of syncope associated with forced exhalation

24
Spirometry
  • Spirometry requires a voluntary maneuver in which
    a seated patient inhales maximally from tidal
    respiration to total lung capacity and then
    rapidly exhales to the fullest extent until no
    further volume is exhaled at residual volume

25
Spirometry
  • The maneuver may be performed in a forceful
    manner to generate a forced vital capacity (FVC)
    or in a more relaxed manner to generate a slow
    vital capacity (SVC).

26
  • In normal persons, the inspiratory vital
    capacity, the expiratory SVC, and expiratory FVC
    are essentially equal. However, in patients with
    obstructive airways disease, the expiratory SVC
    is generally higher than the FVC.

27
Interpretation of spirometry results(1)
  • should begin with an assessment of test quality.
  • to inspect the graphic data
  • (the volume-time curve and the flow-volume loop)

28
Interpretation of spirometry results(2)
  • to ascertain whether the study meets certain
    well-defined acceptability and reproducibility
    standards

29
acceptable spirometry (ATS)
  • 1) minimal hesitation at the start of the forced
    expiration (extrapolated volume (EV) lt5 of the
    FVC or 0.15 L, whichever is larger
  • Time to PEF is lt120 ms (optional until further
    information is available)
  • (2) no cough in the first second of forced
    exhalation,
  • 3) meets 1 of 3 criteria that define a valid
    end-of-test

30
Valid end-of-test
  • (a) smooth curvilinear rise of the volume-time
    tracing to a plateau of at least 1-second
    duration
    (b) if a
    test fails to exhibit an expiratory plateau, a
    forced expiratory time (FET) of 15 seconds or

    (c) when the patient
    cannot or should not continue forced exhalation
    for valid medical reasons.

31
  • 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

32
Acceptability Criteria
  • Good start of test
  • No coughing
  • No variable flow
  • No early termination
  • Reproducibility

33
The volume-time tracing
  • The volume-time tracing is most useful in
    assessing whether the end-of-test criteria have
    been met

34
Spirometry
35
Flow-volume loop
  • the flow-volume loop is most valuable in
    evaluating the start-of-test criteria.

36
Flow-Volume Loop
Ruppel GL. Manual of Pulmonary Function Testing,
8th ed., Mosby 2003
37
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

38
  • Well trained technician

39
Lung Volumes
40
Lung Volumes
  • 4 Volumes
  • 4 Capacities
  • Sum of 2 or more lung volumes

IRV
IC
VC
TLC
TV
ERV
FRC
RV
RV
41
Spirometry
42
Lung Factors Affecting Spirometry
  • Mechanical properties
  • Resistive elements

43
Mechanical Properties
  • Compliance
  • Describes the stiffness of the lungs
  • Change in volume over the change in pressure
  • Elastic recoil
  • The tendency of the lung to return to its
    resting state
  • A lung that is fully stretched has more elastic
    recoil and thus larger maximal flows

44
Resistive Properties
  • Determined by airway caliber
  • Affected by
  • Lung volume
  • Bronchial smooth muscles
  • Airway collapsibility

45
Factors That Affect Lung Volumes
  • Age
  • Sex
  • Height
  • Weight
  • Race
  • Disease

46
Technique
  • Have patient seated comfortably
  • Closed-circuit technique
  • Place nose clip on
  • Have patient breathe on mouthpiece
  • Have patient take a deep breath as fast as
    possible
  • Blow out as hard as they can until you tell them
    to stop

47
Terminology
  • Forced vital capacity (FVC)
  • Total volume of air that can be exhaled
    forcefully from TLC
  • The majority of FVC can be exhaled in lt3 seconds
    in normal people, but often is much more
    prolonged in obstructive diseases
  • Measured in liters (L)

48
FVC
  • Interpretation of predicted
  • 80-120 Normal
  • 70-79 Mild reduction
  • 50-69 Moderate reduction
  • lt50 Severe reduction

FVC
49
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

50
FEV1
  • Interpretation of predicted
  • gt75 Normal
  • 60-75 Mild obstruction
  • 50-59 Moderate obstruction
  • lt49 Severe obstruction

FEV1
FVC
51
Terminology
  • Forced expiratory flow 25-75 (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

52
FEF25-75
  • Interpretation of predicted
  • gt60 Normal
  • 40-60 Mild obstruction
  • 20-40 Moderate obstruction
  • lt10 Severe obstruction

53
Flow-Volume Loop
  • Illustrates maximum expiratory and inspiratory
    flow-volume curves
  • Useful to help characterize disease states (e.g.
    obstructive vs. restrictive)

Ruppel GL. Manual of Pulmonary Function Testing,
8th ed., Mosby 2003
54
Categories of Disease
  • Obstructive
  • Restrictive
  • Mixed

55
Obstructive Disorders
  • Characterized by a limitation of expiratory
    airflow
  • Examples asthma, COPD
  • Decreased FEV1, FEF25-75, FEV1/FVC ratio (lt0.8)
  • Increased or Normal TLC

56
Spirometry in Obstructive Disease
  • Slow rise in upstroke
  • May not reach plateau

57
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

58
Restrictive Disease
  • Rapid upstroke as in normal spirometry
  • Plateau volume is low

59
Large Airway Obstruction
  • Characterized by a truncated inspiratory or
    expiratory loop

60
Normal Spirometry
61
Obstructive Pattern
  • Decreased FEV1
  • Decreased FVC
  • Decreased FEV1/FVC
  • - lt70 predicted
  • FEV1 used to follow severity in COPD

62
Obstructive Lung Disease Differential Diagnosis
  • Asthma
  • COPD
  • - chronic bronchitis
  • - emphysema
  • Bronchiectasis
  • Bronchiolitis
  • Upper airway obstruction

63
Restrictive Pattern
  • Decreased FEV1
  • Decreased FVC
  • FEV1/FVC normal or increased

64
Restrictive Lung Disease Differential Diagnosis
  • Pleural
  • Parenchymal
  • Chest wall
  • Neuromuscular

65
Spirometry Patterns
66
Bronchodilator Response
  • Degree to which FEV1 improves with inhaled
    bronchodilator
  • Documents reversible airflow obstruction
  • Significant response if
  • - FEV1 increases by 12 and gt200ml
  • Request if obstructive pattern on spirometry

67
Flow Volume Loop
  • Spirogram
  • Measures forced inspiratory and expiratory flow
    rate
  • Augments spirometry results
  • Indications evaluation of upper airway
    obstruction (stridor, unexplained dyspnea)

68
Flow Volume Loop
69
Upper Airway Obstruction
  • Variable intrathoracic obstruction
  • Variable extrathoracic obstruction
  • Fixed obstruction

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Upper Airway Obstruction
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Lung Volumes
  • Measurement
  • - helium
  • - nitrogen washout
  • - body plethsmography
  • Indications
  • - Diagnose restrictive component
  • - Differentiate chronic bronchitis from
    emphysema

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Pulmonary Function Testing The Basics of
Interpretation
  • Jennifer Hale, M.D.
  • Valley Baptist Family Practice Residency

80
Lung Volumes Patterns
  • Obstructive
  • - TLC gt 120 predicted
  • - RV gt 120 predicted
  • Restrictive
  • - TLC lt 80 predicted
  • - RV lt 80 predicted

81
Diffusing Capacity
  • Diffusing capacity of lungs for CO
  • Measures ability of lungs to transport inhaled
    gas from alveoli to pulmonary capillaries
  • Depends on
  • - alveolarcapillary membrane
  • - hemoglobin concentration
  • - cardiac output

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Diffusing Capacity
  • Decreased DLCO
    (lt80 predicted)
  • Obstructive lung disease
  • Parenchymal disease
  • Pulmonary vascular disease
  • Anemia
  • Increased DLCO
  • (gt120-140 predicted)
  • Asthma (or normal)
  • Pulmonary hemorrhage
  • Polycythemia
  • Left to right shunt

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DLCO Indications
  • Differentiate asthma from emphysema
  • Evaluation and severity of restrictive lung
    disease
  • Early stages of pulmonary hypertension
  • Expensive!

88
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.

89
Continued
  • PFTs FEV1 86 predicted
  • FEV1/FVC 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?

90
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

91
Continued
SYMPTOMS
  • ?

PFTs
?
OBSTRUCTION?
?
?
YES
NO
?
?
BRONCHOPROVOCATION
TREAT
?
?
Obstruction? TREAT
No Obstruction? Other Diagnosis
92
PFT Interpretation Strategy
  • What is the clinical question?
  • What is normal?
  • Did the test meet American Thoracic Society (ATS)
    criteria?
  • Dont forget (or ignore) the flow volume loop!

93
Obstructive Pattern Evaluation
  • Spirometry
  • FEV1, FVC decreased
  • FEV1/FVC decreased (lt70 predicted)
  • FV Loop scooped
  • Lung Volumes
  • TLC, RV increased
  • Bronchodilator responsiveness

94
Restrictive Pattern Evaluation
  • Spirometry
  • FVC, FEV1 decreased
  • FEV1/FVC normal or increased
  • FV Loop witchs hat
  • DLCO decreased
  • Lung Volumes
  • TLC, RV decreased
  • Muscle pressures may be important

95
PFT Patterns
  • Emphysema
  • FEV1/FVC lt70
  • Scooped FV curve
  • TLC increased
  • Increased compliance
  • DLCO decreased
  • Chronic Bronchitis
  • FEV1/FVC lt70
  • Scooped FV curve
  • TLC normal
  • Normal compliance
  • DLCO usually normal

96
PFT Patterns
  • Asthma
  • FEV1/FVC normal or decreased
  • DLCO normal or increased
  • But PFTs may be normal ? bronchoprovocation

97
Pulmonary Function Testing Jennifer Hale, M.D.
  • Which of the following is used to follow disease
    severity in COPD patients?
  • Total lung capacity (TLC)
  • Degree of responsiveness to bronchodilators
  • Forced vital capacity (FVC)
  • Forced expiratory volume in 1 second
  • e. Diffusing capacity (DLCO)

98
Pulmonary Function Testing Jennifer Hale, M.D.
  • Which of the following is used to follow disease
    severity in COPD patients?
  • Total lung capacity (TLC)
  • Degree of responsiveness to bronchodilators
  • Forced vital capacity (FVC)
  • Forced expiratory volume in 1 second
  • e. Diffusing capacity (DLCO)

99
Pulmonary Function Testing Jennifer Hale, M.D.
  • 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?
  • Diffusing Capacity (DLCO)
  • If no obstruction present, add trial of
    bronchodilator
  • If no obstruction present, perform methacholine
    challenge
  • Flow volume loop
  • b and c

100
Pulmonary Function Testing Jennifer Hale, M.D.
  • 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?
  • Diffusing Capacity (DLCO)
  • If no obstruction present, add trial of
    bronchodilator
  • If no obstruction present, perform methacholine
    challenge
  • Flow volume loop
  • b and c

101
Pulmonary Function Testing Jennifer Hale, M.D.
  • 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?
  • Pulmonary edema
  • Aspiration pneumonitis
  • Pulmonary emboli
  • Alveolar hemorrhage
  • e. Interstitial lung disease

102
Pulmonary Function Testing Jennifer Hale, M.D.
  • 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?
  • Pulmonary edema
  • Aspiration pneumonitis
  • Pulmonary emboli
  • Alveolar hemorrhage
  • e. Interstitial lung disease

103
Questions?
104
References
  1. Aboussouan LS, Stoller JK Flow volume loops.
    UpToDate, 2006.
  2. Bahhady IJ, Unterborn J Pulmonary function
    tests an update. Consultant. 2003.
  3. Barreiro, TJ, Perillo I An approach to
    interpreting spirometry. Am Fam Physician. 2004
    Mar 169(5)1107-14.
  4. Chesnutt MS, Prendergast TJ. Current Medical
    Diagnosis and Treatment. New York Appleton and
    Lange, 2006.
  5. Enright PL Diffusing capacity for carbon
    monoxide. UpToDate, 2007.
  6. Enright PL Overview of pulmonary function
    testing in adults. UpToDate, 2007.
  7. Irvin CG Bronchoprovocation testing. UpToDate,
    2006.
  8. West JB. Respiratory Physiology The
    Essentials. Lippincot Williams Wilkins, 2000.
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