Pulmonary Function Tests

Pulmonary Function TestsPulmonary Function Tests

ObjectivesObjectives

Briefly review pulmonary anatomy and Briefly review pulmonary anatomy and physiologyphysiology

Review lung volumes and capacitiesReview lung volumes and capacitiesProvide an overview of pulmonary function Provide an overview of pulmonary function

teststestsDiscuss spirometry and review its clinical Discuss spirometry and review its clinical

applicationsapplications

AnatomyAnatomy

Lungs comprised of Lungs comprised of AirwaysAirwaysAlveoliAlveoli

Weibel ER: Morphometry of the Human Lung. Berlin and New York: Springer-Verlag, 1963

The AirwaysThe Airways

Conducting zone: no Conducting zone: no gas exchange occursgas exchange occursAnatomic dead spaceAnatomic dead space

Transitional zone: Transitional zone: alveoli appear, but are alveoli appear, but are not great in numbernot great in number

Respiratory zone: Respiratory zone: contain the alveolar contain the alveolar sacssacs

The AlveoliThe Alveoli

Approximately 300 Approximately 300 million alveolimillion alveoli

1/3 mm diameter1/3 mm diameter Total surface area if Total surface area if

they were complete they were complete spheres 85 sq. meters spheres 85 sq. meters (size of a tennis court)(size of a tennis court)

Mechanics of BreathingMechanics of Breathing

InspirationInspirationActive processActive process

ExpirationExpirationQuiet breathing: passiveQuiet breathing: passiveCan become activeCan become active

Lung VolumesLung Volumes

IRV

TV

ERV

4 Volumes4 Volumes4 Capacities4 Capacities

Sum of 2 or more Sum of 2 or more lung volumeslung volumes

RV

IC

FRC

VC

TLC

RV

Tidal Volume (TV)Tidal Volume (TV)

IRV

TV

ERV

RV

IC

FRC

VC

TLC

RV

Volume of air Volume of air inspired and inspired and expired during expired during normal quiet normal quiet breathingbreathing

Inspiratory Reserve Volume (IRV)Inspiratory Reserve Volume (IRV)

IRV

TV

ERV

The maximum The maximum amount of air amount of air that can be that can be inhaled after a inhaled after a normal tidal normal tidal volume volume inspirationinspiration

RV

IC

FRC

VC

TLC

RV

Expiratory Reserve Volume (ERV)Expiratory Reserve Volume (ERV)

IRV

TV

ERV

Maximum Maximum amount of air amount of air that can be that can be exhaled from the exhaled from the resting resting expiratory levelexpiratory level

RV

IC

FRC

VC

TLC

RV

Residual Volume (RV)Residual Volume (RV)

IRV

TV

ERV

Volume of air Volume of air remaining in the remaining in the lungs at the end lungs at the end of maximum of maximum expirationexpiration

RV

IC

FRC

VC

TLC

RV

Vital Capacity (VC)Vital Capacity (VC)

IRV

TV

ERV

Volume of air that Volume of air that can be exhaled can be exhaled from the lungs from the lungs after a maximum after a maximum inspirationinspiration

FVC: when VC FVC: when VC exhaled forcefullyexhaled forcefully

SVC: when VC is SVC: when VC is exhaled slowlyexhaled slowly

VC = IRV + TV + VC = IRV + TV + ERVERV

RV

IC

FRC

VC

TLC

RV

Inspiratory Capacity (IC)Inspiratory Capacity (IC)

IRV

TV

ERV

Maximum Maximum amount of air that amount of air that can be inhaled can be inhaled from the end of a from the end of a tidal volumetidal volume

IC = IRV + TVIC = IRV + TV

RV

IC

FRC

VC

TLC

RV

Functional Residual Capacity (FRC)Functional Residual Capacity (FRC)

IRV

TV

ERV

Volume of air Volume of air remaining in the remaining in the lungs at the end of lungs at the end of a TV expiration a TV expiration

The elastic force of The elastic force of the chest wall is the chest wall is exactly balanced by exactly balanced by the elastic force of the elastic force of the lungsthe lungs

FRC = ERV + RVFRC = ERV + RVRV

IC

FRC

VC

TLC

RV

Total Lung Capacity (TLC)Total Lung Capacity (TLC)

IRV

TV

ERV

Volume of air in the Volume of air in the lungs after a lungs after a maximum maximum inspirationinspiration

TLC = IRV + TV + TLC = IRV + TV + ERV + RVERV + RV

RV

IC

FRC

VC

TLC

RV


Evaluates 1 or more major aspects of the Evaluates 1 or more major aspects of the respiratory systemrespiratory systemLung volumesLung volumesAirway functionAirway functionGas exchangeGas exchange

IndicationsIndications

Detect disease Detect disease Evaluate extent and monitor course of Evaluate extent and monitor course of

diseasediseaseEvaluate treatmentEvaluate treatmentMeasure effects of exposuresMeasure effects of exposuresAssess risk for surgical proceduresAssess risk for surgical procedures


Airway functionAirway functionSimple spirometrySimple spirometryForced vital capacity Forced vital capacity

maneuvermaneuverMaximal voluntary Maximal voluntary

ventilationventilationMaximal Maximal

inspiratory/expiratory inspiratory/expiratory pressurespressures

Airway resistanceAirway resistance

Lung volumes and Lung volumes and ventilationventilation Functional residual Functional residual

capacitycapacity Total lung capacity, Total lung capacity,

residual volumeresidual volume Minute ventilation, Minute ventilation,

alveolar ventilation, alveolar ventilation, dead spacedead space

Distribution of Distribution of ventilationventilation

Pulmonary Function Tests Pulmonary Function Tests

Diffusing capacity Diffusing capacity teststests

Blood gases and gas Blood gases and gas exchange testsexchange tests

Blood gas analysisBlood gas analysisPulse oximetryPulse oximetryCapnographyCapnography

Cardiopulmonary Cardiopulmonary exercise testsexercise tests

Metabolic Metabolic measurements measurements Resting energy Resting energy

expenditureexpenditure Substrate utilizationSubstrate utilization

Chemical analysis of Chemical analysis of exhaled breathexhaled breath

SpirometrySpirometry

Measurement of the pattern of air Measurement of the pattern of air movement into and out of the lungs during movement into and out of the lungs during controlled ventilatory maneuvers.controlled ventilatory maneuvers.

Often done as a maximal expiratory Often done as a maximal expiratory maneuver maneuver

ImportanceImportance

Patients and physicians have inaccurate Patients and physicians have inaccurate perceptions of severity of airflow perceptions of severity of airflow obstruction and/or severity of lung disease obstruction and/or severity of lung disease by physical examby physical exam

Provides objective evidence in identifying Provides objective evidence in identifying patterns of diseasepatterns of disease

Lung Factors Affecting SpirometryLung Factors Affecting Spirometry

Mechanical properties Mechanical properties Resistive elementsResistive elements

Mechanical PropertiesMechanical Properties

ComplianceComplianceDescribes the stiffness of the lungsDescribes the stiffness of the lungsChange in volume over the change in pressureChange in volume over the change in pressure

Elastic recoilElastic recoilThe tendency of the lung to return to it’s resting The tendency of the lung to return to it’s resting

statestateA lung that is fully stretched has more elastic A lung that is fully stretched has more elastic

recoil and thus larger maximal flowsrecoil and thus larger maximal flows

Resistive PropertiesResistive Properties

Determined by airway caliberDetermined by airway caliberAffected byAffected by

Lung volumeLung volumeBronchial smooth musclesBronchial smooth musclesAirway collapsibilityAirway collapsibility

Factors That Affect Lung VolumesFactors That Affect Lung Volumes

AgeAgeSexSexHeightHeightWeightWeightRaceRaceDiseaseDisease

TechniqueTechnique

Have patient seated comfortablyHave patient seated comfortablyClosed-circuit techniqueClosed-circuit technique

Place nose clip onPlace nose clip onHave patient breathe on mouthpieceHave patient breathe on mouthpieceHave patient take a deep breath as fast as Have patient take a deep breath as fast as

possiblepossibleBlow out as hard as they can until you tell them Blow out as hard as they can until you tell them

to stopto stop

TerminologyTerminology

Forced vital capacity Forced vital capacity (FVC):(FVC):Total volume of air that can Total volume of air that can

be exhaled forcefully from be exhaled forcefully from TLCTLC

The majority of FVC can be The majority of FVC can be exhaled in <3 seconds in exhaled in <3 seconds in normal people, but often is normal people, but often is much more prolonged in much more prolonged in obstructive diseasesobstructive diseases

Measured in liters (L)Measured in liters (L)

FVCFVC

Interpretation of % predicted:Interpretation of % predicted:80-120%80-120% NormalNormal70-79%70-79% Mild reductionMild reduction50%-69%50%-69% Moderate reductionModerate reduction<50%<50% Severe reductionSevere reduction

FVC


Forced expiratory volume Forced expiratory volume in 1 second: (FEVin 1 second: (FEV11))Volume of air forcefully Volume of air forcefully

expired from full inflation expired from full inflation (TLC) in the first second(TLC) in the first second

Measured in liters (L)Measured in liters (L)Normal people can exhale Normal people can exhale

more than 75-80% of their more than 75-80% of their FVC in the first second; FVC in the first second; thus the FEV1/FVC can be thus the FEV1/FVC can be utilized to characterize lung utilized to characterize lung diseasedisease

FEVFEV11

Interpretation of % predicted:Interpretation of % predicted:>75%>75% NormalNormal60%-75%60%-75% Mild obstructionMild obstruction50-59%50-59% Moderate obstructionModerate obstruction<49%<49% Severe obstructionSevere obstruction

FEV1 FVC


Forced expiratory flow 25-Forced expiratory flow 25-75% (FEF75% (FEF25-7525-75))Mean forced expiratory flow Mean forced expiratory flow

during middle half of FVC during middle half of FVC Measured in L/secMeasured in L/secMay reflect effort independent May reflect effort independent

expiration and the status of expiration and the status of the small airwaysthe small airways

Highly variableHighly variableDepends heavily on FVCDepends heavily on FVC

FEFFEF25-7525-75

Interpretation of % predicted:Interpretation of % predicted:>60%>60% NormalNormal40-60%40-60% Mild obstructionMild obstruction20-40%20-40% Moderate obstructionModerate obstruction<10%<10% Severe obstructionSevere obstruction

Acceptability CriteriaAcceptability Criteria

Good start of testGood start of testNo coughingNo coughingNo variable flowNo variable flowNo early terminationNo early terminationReproducibilityReproducibility

Flow-Volume LoopFlow-Volume Loop

Illustrates maximum Illustrates maximum expiratory and expiratory and inspiratory flow-inspiratory flow-volume curvesvolume curves

Useful to help Useful to help characterize disease characterize disease states (e.g. obstructive states (e.g. obstructive vs. restrictive)vs. restrictive)

Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003

Categories of DiseaseCategories of Disease

ObstructiveObstructiveRestrictiveRestrictiveMixedMixed

Obstructive DisordersObstructive Disorders

Characterized by a Characterized by a limitation of expiratory limitation of expiratory airflowairflow Examples: asthma, Examples: asthma,

COPDCOPD Decreased: FEVDecreased: FEV11, ,

FEFFEF25-7525-75, FEV, FEV11/FVC /FVC ratio (<0.8)ratio (<0.8)

Increased or Normal: Increased or Normal: TLCTLC

Spirometry in Obstructive DiseaseSpirometry in Obstructive Disease

Slow rise in upstrokeSlow rise in upstrokeMay not reach plateauMay not reach plateau

Restrictive Lung DiseaseRestrictive Lung Disease

Characterized by diminished lung Characterized by diminished lung volume due to:volume due to:change in alteration in lung change in alteration in lung

parenchyma (interstitial lung parenchyma (interstitial lung disease) disease)

disease of pleura, chest wall (e.g. disease of pleura, chest wall (e.g. scoliosis), or neuromuscular scoliosis), or neuromuscular apparatus (e.g. muscular apparatus (e.g. muscular dystrophy)dystrophy)

Decreased TLC, FVCDecreased TLC, FVCNormal or increased: FEVNormal or increased: FEV11/FVC /FVC

ratioratio

Restrictive DiseaseRestrictive Disease

Rapid upstroke as Rapid upstroke as in normal in normal spirometryspirometry

Plateau volume is Plateau volume is lowlow

Large Airway ObstructionLarge Airway Obstruction

Characterized by a Characterized by a truncated inspiratory truncated inspiratory or expiratory loopor expiratory loop

Lung VolumesLung Volumes

Measured through various methodsMeasured through various methodsDilutional: helium, 100% oxygenDilutional: helium, 100% oxygenBody plethysmographyBody plethysmography

Changes in Lung Volumes in Various Changes in Lung Volumes in Various Disease StatesDisease States

Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003

Clinical ApplicationsClinical Applications

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Pulmonary Function Tests