Chapter 3 · 2011-01-05 · Mosby items and derived items © 2011, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 3 Normal Lung Volumes and Capacities

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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)