2. Professor of Internal Medicine Department of Pulmonary Medicine
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.

10. 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.

16. 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
Significant CXR findings include hyperinflation, increased interstitial markings, enlarged pulmonary arteries. Significant ECG findings include evidence of pulmonary HTN or COPD
(What might ECG show in a COPD patient? MAT, WAP, others)
Significant findings on ABG are hypoxemia or hypercapnia; elevated Hb may also be evident on CBC.

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 > 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
Preop assessment is rarely to tell surgeon not to operate, but to prepare for pulmonary complications such as pneumonia, prolonged mechanical ventilation, etc. Also for screening: this includes all current and former smokers >45yoa, known COPD or asthma pts, also those scheduled for thoracic or upper abdominal surgery. If mod-severe obstruction identified and surgery can be delayed, can start prophylactic program of pulmonary hygiene, stop smoking, give inhaled bronchodilators or steroids, etc.

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) <5% of the FVC or 0.15 L, whichever is larger
Time to PEF is <120 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
Image source:

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
Image source:

40. Lung Volumes 4 Volumes 4 Capacities Sum of 2 or more lung volumes IRVIC VC
TLC TV
ERV
FRC RV RV

41. Spirometry
Image source:

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 it’s 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 <3 seconds in normal people, but often is much more prolonged in obstructive diseases
Measured in liters (L)

48. FVC FVC Interpretation of % predicted: 80-120% Normal
70-79% Mild reduction
50%-69% Moderate reduction
<50% 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 FVC FEV1 Interpretation of % predicted: >75% Normal
60%-75% Mild obstruction
50-59% Moderate obstruction
<49% 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: >60% Normal
40-60% Mild obstruction
20-40% Moderate obstruction
<10% 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 (<0.8)
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
Image source:

61. Obstructive Pattern Decreased FEV1 Decreased FVC Decreased FEV1/FVC
- <70% predicted
FEV1 used to follow severity in COPD
Image source:
FEV1 is decreased out of proportion to FVC, which causes the ratio to decrease as well.

62. Obstructive Lung Disease — Differential Diagnosis
Asthma
COPD
- chronic bronchitis
- emphysema
Bronchiectasis
Bronchiolitis
Upper airway obstruction
This is not a complete list, just some of the most common diseases that should be on your differential for obstructive lung disease.

63. Restrictive Pattern Decreased FEV1 Decreased FVC
FEV1/FVC normal or increased
Image source:
FEV1 decreases in proportion to decrease in FVC, so ratio remains normal or even slightly increased

64. Restrictive Lung Disease —Differential Diagnosis
Pleural
Parenchymal
Chest wall
Neuromuscular
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.

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 >200ml
Request if obstructive pattern on spirometry
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.
HOLD MDI THE MORNING PRIOR TO TESTING.

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

68. Flow Volume Loop
Image source:
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.

69. Upper Airway Obstruction
Variable intrathoracic obstruction
Variable extrathoracic obstruction
Fixed obstruction
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).

70. Upper Airway Obstruction

75. Lung Volumes Measurement: - helium Indications:
- nitrogen washout
- body plethsmography
Indications:
- Diagnose restrictive component
- Differentiate chronic bronchitis from emphysema
FVC is decreased in both obstructive and restrictive disease, so usually need to obtain lung volumes to see if restrictive component present (increased TLC).

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

80. Lung Volumes – Patterns
Obstructive
- TLC > 120% predicted
- RV > 120% predicted
Restrictive
- TLC < 80% predicted
- RV < 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:
- alveolar—capillary membrane
- hemoglobin concentration
- cardiac output
Measure of gas exchange at alveolar-capillary membrane.
Changes in DLCO are one of the earliest signs of interstitial lung disease (ILD).

82. Image source: http://www.alf3.urz.unibas.ch/pathopic/e/intro.htm
Normal alveolar-capillary membrane.

83. Image source: http://www.alf3.urz.unibas.ch/pathopic/e/intro.htm
Normal lung parenchyma.

84. Diffusing Capacity Decreased DLCO (<80% predicted) Increased DLCO
Obstructive lung disease
Parenchymal disease
Pulmonary vascular disease
Anemia
Increased DLCO
(> % predicted)
Asthma (or normal)
Pulmonary hemorrhage
Polycythemia
Left to right shunt
Pulmonary vascular disease = pulmonary emboli, pulmonary HTN.
Low DLCO is also a major predictor of desaturation during exercise.

85. Image source: http://www.alf3.urz.unibas.ch/pathopic/e/intro.htm
Emphysematous lung parenchyma—evidence of destroyed areas for gas exchange, causing a decreased DLCO.

86. Image source: http://www.alf3.urz.unibas.ch/pathopic/e/intro.htm
IPF, with thickening of interstitial spaces, also a cause of decreased DLCO.

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

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
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.

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?
Don’t forget (or ignore) the flow volume loop!
Now we’re going to put it all together…

93. Obstructive Pattern — Evaluation
Spirometry
FEV1, FVC: decreased
FEV1/FVC: decreased (<70% predicted)
FV Loop “scooped”
Lung Volumes
TLC, RV: increased
Bronchodilator responsiveness
Don’t need a DLCO, but if were decreased would make you think emphysema, if normal then chronic bronchitis.

94. Restrictive Pattern – Evaluation
Spirometry
FVC, FEV1: decreased
FEV1/FVC: normal or increased
FV Loop “witch’s hat”
DLCO decreased
Lung Volumes
TLC, RV: decreased
Muscle pressures may be important
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

95. PFT Patterns Emphysema Chronic Bronchitis FEV1/FVC <70%
“Scooped” FV curve
TLC increased
Increased compliance
DLCO decreased
Chronic Bronchitis
FEV1/FVC <70%
“Scooped” FV curve
TLC normal
Normal compliance
DLCO usually normal
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.

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)
In COPD patients, the FEV1 is used to classify severity of obstructive lung disease, and followed to assess progression.

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
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.

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
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.

103. Questions?

104. References
Aboussouan LS, Stoller JK: Flow volume loops. UpToDate, 2006.
Bahhady IJ, Unterborn J: Pulmonary function tests: an update. Consultant
Barreiro, TJ, Perillo I: An approach to interpreting spirometry. Am Fam Physician Mar 1;69(5):
Chesnutt MS, Prendergast TJ. Current Medical Diagnosis and Treatment. New York: Appleton and Lange, 2006.
Enright PL: Diffusing capacity for carbon monoxide. UpToDate, 2007.
Enright PL: Overview of pulmonary function testing in adults. UpToDate, 2007.
Irvin CG: Bronchoprovocation testing. UpToDate, 2006.
West JB. Respiratory Physiology: The Essentials. Lippincot Williams & Wilkins, 2000.