Chapter 19 Pulmonary Function Testing

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

Chapter 19

Pulmonary Function Testing


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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Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 7

All of the following are contraindications to pulmonary function testing, except:

A. Hypertension

B. Pneumothorax

C. Pulmonary Embolism

D. Myocardial Infarction


Pathophysiologic Patterns

• Two major categories of pulmonary disease exist: ObstructiveRestrictive

• 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 volumeMeasure 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


Principles of Measurement

• Most pulmonary function laboratories have 3 components.1. Performing spirometry to measure airway

mechanics2. Measuring lung volumes & capacities3. 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 mechanicsForced vital capacity (FVC)Forced expiratory volume in 1 second (FEV1)

Other forced expiratory flow measurementsMaximum 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. Forced expiratory flow measurements (FEV1)

B. Forced vital capacity (FVC)

C. Maximum voluntary ventilation (MVV)

D. Helium dilution technique


Maximal Voluntary Ventilation (MVV)

• Effort-dependent test; patient asked to breathe deep & fast for 12 seconds

• Results reflect:Patient effortFunction of respiratory musclesAbility of chest wall to expandPatency 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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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. Obstructive disease

B. Obstructive and restrictive disease

C. Restrictive disease

D. Patient is in the normal range


Lung Volumes & Capacities

Lung VolumesTidal volumeInspiratory reserve

volumeExpiratory reserve

volumeResidual volume

Lung CapacitiesTotal lung capacityInspiratory capacityFunctional residual

capacityVital capacity

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Lung Volumes & Capacities (cont.)

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The functional residual capacity consist of which two lung volumes

A. Tidal volume and inspiratory reserve volume

B. Tidal volume and expiratory reserve volume

C. Inspiratory reserve volume and residual volume

D. Expiratory reserve volume and residual volume


Techniques for Measuring RV

• Helium dilutionBased on fact that known amount of helium will be

diluted by size of patient’s RV

• Nitrogen washoutBased on fact that 79% of RV is nitrogenVolume of nitrogen exhaled ÷ 0.79 = RV

• Body boxApplies 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• Carboxyhemoglobin• Pulmonary

Embolism• Diffused pulmonary

fibrosis• Pulmonary

emphysema

Factors that Increase DLCO

PolycythemiaExerciseCongestive 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. Polycythemia.

B. Exercise.

C. Congestive heart failure.

D. Pulmonary emphysema.


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 presentReduced surface area = emphysemaThickened AC membrane = pulmonary fibrosis

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PFT Report Interpretation

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Interpretation

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Chapter 19 Pulmonary Function Testing

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