Chapter 19
Pulmonary Function Testing
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Learning Objectives
• List the three categories of pulmonary function
tests.
• State the primary purposes of pulmonary
function testing.
• Describe the pathophysiologic patterns
associated with obstructive and restrictive lung
disease.
• State what is meant by the term spirometer, and
list the parameters that can be measured by it.
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Learning Objectives (cont.)
• List and describe the four general principles that
should be considered for tests of pulmonary
function.
• List and describe the measurements that
indicate pulmonary mechanics.
• Describe the purpose and technique for the
bronchial challenge test.
• List and describe the four volumes and four
capacities that can be measured with pulmonary
function testing.
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Learning Objections (cont.)
• Describe the purpose and techniques used to
measure diffusion capacity.
• Interpret pulmonary function reports.
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PFTs will measure:
• Dynamic flow rates of gases through airways,
• Lung volumes & capacities
• Ability of lungs to diffuse gases
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Purposes of PFT
• Identify & quantify changes in pulmonary
function due to disease
• Evaluate effectiveness of therapy
• Perform epidemiological surveillance for
pulmonary disease
• Assess patients for risk of postoperative
complications
• Determine pulmonary disability
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All of the following are contraindications to
pulmonary function testing, except:
A.
B.
C.
D.
Hypertension
Pneumothorax
Pulmonary Embolism
Myocardial Infarction
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Pathophysiologic Patterns
• Two major categories of pulmonary disease
exist:
 Obstructive
 Restrictive
• Primary abnormality in obstructive disease is
increased airways resistance
• Primary problem in restrictive disease is
decrease in either lung compliance or lung
volumes or both
• Some pulmonary diseases cause both
obstructive & restrictive disease
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Pathophysiologic Patterns
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PFT Equipment
• Two general types of measuring devices exist,
those that:
 Measure volume
 Measure flow
• Volume-measuring devices - spirometers
• Flow-measuring devices - pneumotachometers
• Every measuring device has capacity, accuracy,
error, resolution, precision, linearity, & output
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Elements of Quality Assurance



Accuracy & precision of measuring
instruments
Performance of Respiratory Therapist (RT)
Test results when measuring a standard
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All of the following are pathophysiological patterns
of pulmonary diseases, except:
A. Restrictive diseases will decrease lung
compliance
B. Obstructive diseases will increase airway
resistance
C. Restrictive disease will increase lung volumes
D. Some pulmonary diseases can cause both
obstructive and restrictive disease
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Principles of Measurement
• Most pulmonary function laboratories have 3
components.
1. Performing spirometry to measure airway
mechanics
2. Measuring lung volumes & capacities
3. Measuring diffusion capacity of lung
• All 3 components are required when purpose of PFT is
to identify presence & degree of pulmonary impairment
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Spirometry
• Tests of pulmonary mechanics
 Forced vital capacity (FVC)
 Forced expiratory volume in 1 second (FEV1)
 Other forced expiratory flow measurements
 Maximum voluntary ventilation
• These measurements assess ability of lungs to
move large volumes of air quickly through
airways
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Forced Vital Capacity
• Most common test of pulmonary mechanics
• Many measurements are made while patient is
performing FVC maneuver
• FVC is an effort-dependent maneuver requiring
careful patient instruction & cooperation
• To ensure validity, each patient must perform at
least 3 acceptable FVC maneuvers
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Forced Vital Capacity (cont.)
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Other Measures of Pulmonary
Mechanics
• FEV1 - volume of gas exhaled in first 1-second
of FVC maneuver
• FEV1/FVC - calculated by dividing largest FEV1
by largest FVC
• FEF200-1200 - average flow rate early in FVC
maneuver
• FEF25-75 - measure of flow during middle 50% of
FVC
• PEFR - highest point on flow-volume graph
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Pulmonary Mechanics
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Pulmonary Mechanics
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Pulmonary Mechanics
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What is the most commonly used test of
pulmonary mechanics:
A.
B.
C.
D.
Forced expiratory flow measurements (FEV1)
Forced vital capacity (FVC)
Maximum voluntary ventilation (MVV)
Helium dilution technique
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Maximal Voluntary Ventilation (MVV)
• Effort-dependent test; patient asked to breathe
deep & fast for 12 seconds
• Results reflect:
 Patient effort
 Function of respiratory muscles
 Ability of chest wall to expand
 Patency of airways
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The MVV (cont.)
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Quality Assurance of Spirometry

3.0 L syringe used for accuracy & precision of
volume or flow




Multiple strokes at various injection speeds
Average volume should meet the +/- 3% standard
95% expected performance range should be
determined
Technologist performance should be
observed & reviewed periodically
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Significance of Results
• Normal FEV1 = 5.6 L for average 20-year-old
man
• FEV1 is reduced with both obstructive &
restrictive lung disease.
• FEV1/FVC should be at least 70%
 Reduced with obstructive disease
 Normal with restrictive disease
• Other measures of expiratory flow are also
reduced when obstructive disease is present
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Significance of Results (cont.)
• Normal MVV for males is 160 to 180 L/min &
slightly lower in females
• MVV is reduced in patients with moderate to
severe obstructive lung disease
• MVV may be normal or slightly reduced in
patients with restrictive disease
• Undernourished patients may have reduced
MVV
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Obstructive & Restrictive Disorders
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Obstructive & Restrictive Disorders
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Obstructive & Restrictive Disorders
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Reversibility
• If obstruction is present, reversibility must be
evaluated
• Done by performing spirometry before & after
therapy
• Bronchodilator is administered by small-volume
nebulizer or MDI
• Reversibility indicates effective therapy
• Reversibility is defined as 15% or greater
improvement in FEV1 & at least 200-ml increase
in FEV1
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If FEV1/FVC is less than 70%, this would indicate;
A.
B.
C.
D.
Obstructive disease
Obstructive and restrictive disease
Restrictive disease
Patient is in the normal range
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Lung Volumes & Capacities
 Lung Volumes
 Tidal volume
 Inspiratory reserve
volume
 Expiratory reserve
volume
 Residual volume
 Lung Capacities
 Total lung capacity
 Inspiratory capacity
 Functional residual
capacity
 Vital capacity
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Lung Volumes & Capacities (cont.)
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The functional residual capacity consist of which
two lung volumes
A.
B.
C.
D.
Tidal volume and inspiratory reserve volume
Tidal volume and expiratory reserve volume
Inspiratory reserve volume and residual volume
Expiratory reserve volume and residual volume
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Techniques for Measuring RV
• Helium dilution
 Based on fact that known amount of helium will be
diluted by size of patient’s RV
• Nitrogen washout
 Based on fact that 79% of RV is nitrogen
 Volume of nitrogen exhaled ÷ 0.79 = RV
• Body box
 Applies Boyle’s law to measure RV
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Quality Assurance for Measuring
Lung Volume

Helium dilution & nitrogen washout




Accuracy & precision of volume & flow measuring
device
Accuracy & linearity of gas analyzer
Leak test must be acceptable range
Plethysmography

Box & mouth pressure transducers must be
calibrated & accurate
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Helium Dilution
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Nitrogen Washout
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Body Plethymography
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Significance of Results
• TLC, FRC, & RV increase with obstructive
disease & decrease with restrictive impairment
• Normal tidal volume is 500 to 700 ml (5 to 8
ml/kg of predicted body weight); VT
measurement alone not helpful
• Normal TLC is about 6 L
• Normal VC is about 4.8 L in adult; results vary
with age, gender, height, & ethnicity
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Changes With Lung Disease
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Diffusing Capacity
• Most PF labs use carbon monoxide to measure
the diffusion capacity of the lungs
• Results reported in ml/min/mm Hg
• Results may be low in both obstructive &
restrictive lung disease
• Emphysema & pulmonary fibrosis are two
common causes of reduced DLCO
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Single Breath Technique
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Interpreting the DLCO
Factors that Decrease DLCO
• Anemia
• Carboxyhemoglobi
n
• Pulmonary
Embolism
• Diffused pulmonary
fibrosis
• Pulmonary
emphysema
Factors that Increase DLCO
 Polycythemia
 Exercise
 Congestive heart
failure
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Quality Assurance for Measuring
Diffusing Capacity




Accuracy & precision of volume or flow
measuring device
Accuracy & linearity of gas analyzer
Test acceptability & repeatability
Measuring diffusing capacity of 3.0 L to
provide quality control standard
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Which one of these factors can decrease the
diffusing capacity of the lung:
A.
B.
C.
D.
Polycythemia.
Exercise.
Congestive heart failure.
Pulmonary emphysema.
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PFT Report Interpretation
• FEV1/FVC ratio is good place to start; reduced
(<70%) with obstructive lung disease
• If TLC less than 80% of predicted normal &
FEV1/FVC is normal - restrictive disease is
present
• If DLCO is <80% of normal - diffusion defect is
present
 Reduced surface area = emphysema
 Thickened AC membrane = pulmonary fibrosis
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PFT Report Interpretation
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Interpretation
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