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Chapter 3
Pulmonary Function Study
Assessments
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Introduction
Pulmonary function studies are used to: Evaluate pulmonary causes of dyspnea
Differentiate between obstructive and restrictive
pulmonary disorders
Assess severity of the pathophysiologic
impairment
Follow the course of a particular disease
Evaluate the effectiveness of therapy
Assess the patient’s preoperative status
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Normal Lung Volumes
and Capacities
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Table 3-1. Lung Volumes and Capacities of Normal Recumbent Subjects 20 to 30 Years of Age
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Table 3-2. Restrictive Lung Disorders: Lung Volume and Capacity Findings
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Table 3-4. Obstructive Lung Disorders: (Lung Volume and Capacity Findings)
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Table 3-5. Anatomic Alterations of the Lungs Associated with Obstructive Lung Disorders:
(Pathology of the Tracheobronchial Tree)
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Figure 3-1. Visual comparison of lung volumes and capacities in obstructive and restrictive lung disorders. (From Wilkins RL, Stoller JK, Scanlan CL: Egan’s fundamentals
of respiratory care, ed 9, St Louis, 2009, Elsevier.)
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Indirect Measurements of the Residual
Volume and Capacities Containing the
Residual Volume
Closed-circuit helium dilution test
Open-circuit nitrogen washout test
Body plethysmography
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Forced Expiratory Flow Rate
and Volume Measurements
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Forced Vital Capacity (FVC)
The FVC is the total volume of gas that can
be exhaled as forcefully and rapidly as
possible after a maximal inspiration.
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Figure 3-2. Forced vital capacity (FVC). A is the point of maximal inspiration and the starting point of an FVC maneuver. Note the reduction in FVC in
obstructive pulmonary disease.
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Forced Expiratory Volume (FEVT)
The maximum volume of gas that can be
exhaled over a specific period is the FEVT.
This measurement is obtained from an FVC
measurement.
Commonly used time periods are 0.5, 1.0,
2.0, 3.0, and 6.0 seconds
The most commonly used time is 1 second
(FEV1 ).
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Figure 3-3. Forced expiratory volume timed (FEVT). In obstructive pulmonary disease, more time is needed to exhale
a specified volume.
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Forced Expiratory Volume (FEVT)
(Cont’d)
In the normal adult, the percentage of total
volume exhaled during these time periods: FEV0.5: 60%
FEV1: 80%
FEV2: 94%
FEV3: 97%
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Forced Expiratory Volume in 1
Second/Forced
Vital Capacity Ratio
(FEV1/FVC Ratio)
(also abbreviated as FEV1%)
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FEV1/FVC Ratio
or
FEV1%
The FEV1/FVC ratio compares the amount of
air exhaled in 1 second with the total amount
exhaled during an FVC maneuver.
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FVC, FEV1, and FEV1%
Clinically, the FVC, FEV1, and FEV1% are
commonly used to:
1. Assess the severity of a patient’s pulmonary
disorder and
2. Determine whether the patient has an
obstructive or a restrictive disease
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FVC, FEV1, and FEV1% (Cont’d)
The primary pulmonary function study
difference between an obstructive and a
restrictive lung disorder are as follows: In an obstructive disorder, the FEV1 and FEV1%
are both decreased.
In a restrictive disorder, the FEV1 is decreased
and FEV1% is normal or increased.
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Forced Expiratory Flow25%-75%
The FEF25%-75% is the average flow rate
generated by the patient during the middle
50% of an FVC measurement.
FEF25%-75% is used to evaluate the status of
medium-to-small airways in obstructive lung
disorders.
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Figure 3-4. FEF25%-75%. This test measures the average rate of flow between 25% and 75% of an FVC.
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Forced Expiratory Flow200-1200
The FEF200-1200 measures the average flow
rate between 200 and 1200 mL of an FVC.
The FEF200-1200 provides a good assessment
of the large upper airways.
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Forced Expiratory Flow200-1200
(Cont’d)
The FEF200-1200 measures the average flow
rate between 200 and 1200 mL of an FVC.
The FEF200-1200 provides a good assessment
of the large upper airways.
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Figure 3-5. FEF200-1200. This test measures the average rate of flow between 200 mL and 1200 mL of an FVC.
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Peak Expiratory Flow Rate
The PEFR is the maximum flow rate
generated during an FVC maneuver.
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Figure 3-6. PEFR. The steepest slope of the DV/DT line is the PEFR (V).˙˙
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Maximum Voluntary Ventilation
(MVV)
The MVV is the largest volume of gas that
can be breathed voluntarily in and out of the
lungs in 1 minute. Note: The patient effort during the MVV is for only
12 to 15 seconds. The total 1 minute MVV is
extrapolated from these data.
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Figure 3-7. Volume-time tracing for an MVV maneuver.
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Flow-Volume Loop
The flow-volume loop is a graphic illustration
of both a forced vital capacity (FVC)
maneuver and a forced inspiration volume
(FIV) maneuver.
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Flow-Volume Loop (Cont’d)
Depending of the sophistication of equipment,
several important pulmonary function study
values can be obtained, including:• FVC
• FEVT
• FEF25%-75%
• FEF200-1200
• PEFR
• Peak inspiratory flow rate (PIFR)
• FEF50%
• Instantaneous flow at any given lung volume during
forced inhalation and exhalation
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Figure 3-8. Flow-volume loop.
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Figure 3-9. Flow-volume loop demonstrating the shape change that results from an obstructive lung disorder. The curve on the right represents
intrathoracic airway obstruction.
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Figure 3-7. Volume-time tracing for a maximum voluntary ventilation (MVV) maneuver.
Note: the patient actually performs the MVV maneuver for only 12 sec, not 60 sec.
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Figure 3-10. Flow-volume loop demonstrating the shape change that results from a restrictive lung disorder. Note the symmetric loss of flow and volume.
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Table 3-8. Obstructive Lung Diseases: Forced Expiratory Flow Rate and Volume Findings
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Pulmonary Diffusion Capacity
The pulmonary diffusion capacity of carbon
monoxide (DLCO) measures the amount of
carbon monoxide (CO) that moves across the
alveolar-capillary membrane.
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Table 3-9. Pulmonary Diffusion Capacity of Carbon Monoxide (DLCO)