Pulmonary Function Tests

Wanida Paoin

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Objectives

Review basic pulmonary anatomy and lung volumevolume.Indication for PFTs.Technique and basic interpretation of spirometryspirometry. Difference between obstructive and restrictive l dilung disease. Clinically application

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y pp

Conducting Airways

Air travels via laminar flow through theflow through the conducting airways:• trachea, • lobar bronchi, • segmental bronchi, • b t l b hi• subsegmental bronchi, • small bronchi, • bronchioles andbronchioles, and • terminal bronchioles.

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From Netter Atlas of Human Anatomy, 1989

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Gas Exchange

Capillaries are wrapped around alveoliaround alveoli. Approximately 300 million alveolimillion alveoliAlveolar-capillary barrier: 0.3 μm in some places,0.3 μm in some places, surface area of 50-100 square meters! (size of a

M & N d l T b k f R i(

tennis court) Murray & Nadel: Textbook of Respiratory Medicine, 3rd ed., Copyright © 2000 W. B. Saunders Company

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Lung Volumes

4 Volumes

IRV4 Capacities• Sum of 2 or more

l lIC lung volumesICVC

TLCTV

ERVFRC

TLC

RVFRC

RV

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Pulmonary Function Tests

• Pulse oximetry • Blood gasesBlood gases • End tidal CO2• Spirometry

P k i fl• Peak expiratory flow rate • Bronchial challenge testing • Exercise testsExercise tests • Respiratory muscle pressure measurement• Lung volumes by helium dilution or body

plethysmographyplethysmography• Diffusing capacity

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Pulmonary Function Tests

Evaluates 1 or more major aspects of th i t tthe respiratory system• Lung volumes• Airway function• Gas exchangeg

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Indications

Detect disease Evaluate extent and monitor course of diseaseEvaluate treatmentM ff t fMeasure effects of exposuresAssess risk for surgical proceduresg pAssess bronchial hyperreactivity

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Evaluate extent and monitor Evaluate extent and monitor course of disease

Obstructive disease- asthma- asthma- FB- subglottic, tracheal stenosis

t h l i- tracheomalacia- vascular ring- vocal cord paralysis

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Evaluate extent and monitor Evaluate extent and monitor course of disease

Restictive diseaseRestictive disease- external compression: thoracic cage abnormality, pleural

effusion, pneumothorax, obesity, scoliosisunexpanded lung: interstitial fibrosis pulmonary edema- unexpanded lung: interstitial fibrosis, pulmonary edema

- neuromuscular disease: poliomyelitis, myasthenia grevis

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Importance

Patients and physicians have inaccurate ti f it f i flperceptions of severity of airflow

obstruction and/or severity of lung disease by physical examProvides objective evidence inProvides objective evidence in identifying patterns of disease

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Spirometry

Measurement of the pattern of air movementinto and out of the lungsduring controlled ventilatory maneuvers.

Silhouette of Hutchinson Performing Spirometry, From Chest, 2002

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Limitation

They do not act alone.They do not act alone.They act only to supportor exclude a diagnosisor exclude a diagnosis.

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Mechanical Properties

Compliance• Describes the stiffness of the lungs• volume / pressure

Elastic recoil• The tendency of the lung to return to it’sThe tendency of the lung to return to it s

resting state• A lung that is fully stretched has more elasticA lung that is fully stretched has more elastic

recoil and thus larger maximal flows

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Resistive Properties

Determined by airway caliberAffected by• Lung volumeg• Bronchial smooth muscles• Airway collapsibilityAirway collapsibility

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Factors That Affect Lung Volumes

AgeSexHeightHeightWeightRaceDiseaseDisease

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Special Considerations

Ability to perform spirometry dependent on y p p y pdevelopmental age of child, personality, and interest of the child.Patients need a calm, relaxed environment and good coaching. Patience is key.and good coaching. Patience is key.Even with the best of environments and coaching a child may not be able to performcoaching, a child may not be able to perform spirometry.

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Parameter from spirometer

Spirogram

FVC

PEFR

FVC

FEV1FEF25 75FEF25-75

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Flow-Volume Curve

TechniqueGive instructions and demonstratePatient performs the maneuver

Acceptable criteria< 10 y: > 3 min > 10 y: > 6 minPatient performs the maneuver

• Sit / Stand direct• Puts nose clip on

> 10 y: > 6 minor no more volume > 1 minNot inhaleNo air leak• Inhales maximally

• Puts mouthpiece on mouth and closes lips around mouthpiece

No air leakNo pause

2 maximum FVC different < 10%p• Exhales as hard and fast and long as possible• Repeat minimum of three times (check for

reproducibility )

2 maximum FVC different < 10%

reproducibility.)• Use the best value for interpretation as %predicted of

control (age, height, sex, race)

20(adapted from ATS, 1994)

FVC

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

be exhaled forcefully from be e a ed o ce u y oTLC

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

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FEV1

Forced expiratory volume in 1 second:volume in 1 second: (FEV1)• Volume of air forcefully

expired from full inflation (TLC) in the first second

• Normal people can exhaleNormal people can exhale more than 80% of their FVC in the first second (FEV /FVC)(FEV1/FVC)

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FEF25-75

Forced expiratory flow 25-75% (FEF )75% (FEF25-75)• Mean forced expiratory flow

during middle half of FVC du g dd e a o C• May reflect effort independent

expiration and the status of the small airways

• Highly variable• D d h il FVC• Depends heavily on FVC

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PEFR

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PEFR

Peak flow meter deviceTechniqueTechnique • Sit/Stand direct• Inhales maximallyy• Puts mouthpiece on mouth and closes lips around

mouthpiece• Blow out as hard and fast as possibleGreen : > 80%Blow out as hard and fast as possible• Repeat minimum of three times • Use the best value for interpretation as %predicted /

personal best

Yellow : 50-79%Red : < 50% Normal < 20%

Normal < 12%personal best • Clinical application: monitor severity, daily variability,

pre and post bronchodilator

Normal < 12%

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Categories of Disease

ObstructiveRestrictiveMixedMixed

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FVC

Interpretation of % predicted:• 80 % Normal• 70-79% Mild reduction• 50%-69% Moderate reduction• <50% Severe reduction

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FEV1

Interpretation of % predicted:• >80% Normal• 65-79% Mild obstruction• 50-64% Moderate obstruction• <49% Severe obstruction

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Spirometry Interpretation:

% predictedFVC > 80%FEV1 > 80%FEF25-75% > 70%25-75%

PEFR > 80%FEV1/FVC > 80% absolute valueFEV1/FVC > 80% absolute value

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Spirometry in Obstructive Spirometry in Obstructive Disease

Slow rise in upstrokeM t hMay not reach plateau

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Restrictive Disease

Rapid upstroke p pas in normal spirometryp yPlateau volume is lowo

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S i t I t t ti Ob t tiSpirometry Interpretation: Obstructive vs. Restrictive DefectWhat parameter is the most sensitive in airway obstruction?

Parameter Obstructive Disorders

Restrictive Disorders

What parameter is the most sensitive in airway obstruction?

Disorders DisordersFVC N or ↓ ↓

FEV1

FEF

↓ ↓

NFEF25-75%

FEV1/FVC

↓ N to ↓

↓ N or ↑

PEFR

↓ o ↑

↓ N to ↓

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Spirometry Interpretation:Obstructive Disorders• Characterized by a

Restrictive Disorders• Characterized by y

limitation of expiratory airflow

Examples:

yreduced lung volumes/decreased lung compliancea p es

• Asthma• Bronchiectasis • COPD

Examples:• Interstitial Fibrosis• Kyphoscoliosis• COPD

• Cystic FibrosisKyphoscoliosis

• Obesity• Lung Resection• Neuromuscular diseases• Cystic Fibrosis

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Fl V l LFlow-Volume LoopPEFR

Do FVC maneuver and then inhale as

flow

and then inhale as rapidly and as much as ableexpiration as able.The expiratory and inspiratory flow

volumeinspiration

inspiratory flow volume curves put together make a flowtogether make a flow volume loop.RVTLC

34Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003

Restrictive Lung Disease

Ch t i d bCharacterized by diminished lung volume Decreased TLC FVCDecreased TLC, FVCNormal or increased: FEV1/FVC ratioFEV1/FVC ratio

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Obstructive Lung Disease

Characterized by a limitation of expiratorylimitation of expiratory airflow• Examples: asthma, a p es ast a,

COPD

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Large Airway Obstruction

Characterized by a truncatedtruncated inspiratory or expiratory loopexpiratory loop

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Flow-Volume LoopsL1 R1

L2 R2R2

L3 R3

Variable intrathoracic ob

Incomplete exhalationVariable extrathoracic ob

L4 Variable intrathoracic obFixed central or up aw ob

Inadq effortRestricti e l ng disease

38(Rudolph and Rudolph, 2003)

Restrictive lung disease

Spirometry: Pre and Post Bronchodilator

Obtain spirogram and flow-volume loop.Pre and 15 minutes after administration ofPre and 15 minutes after administration of the bronchodilator Salbutamol MDI 4 puffs via valve spacerSalbutamol MDI 4 puffs via valve spacer • Slow inhale• Breath hold 5-10 secBreath hold 5-10 sec.• 5-10 sec pause between each puff.

Reversibility: FEV1 / PEFR > 12%Reversibility: FEV1 / PEFR > 12% Improve flow-volume loop.

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PEFR

Inhales maximallyyExhales as hard and fast and short as possibleRepeat minimum of three times pUse the best value for interpretation as %predicted of control / personal bestHighly effort dependentDiurnal variation (normal < 20%)Different value in each devices

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Exercise challenge test

Perform spirometryPerform spirometryExercise 6-8 min (tread mill) till HR

/160-180/minRepeat spirometry at 5, 10, 15, 20, 30Repeat spirometry at 5, 10, 15, 20, 30 minEIB FEV 10 15% h iEIB: FEV1 10-15%, or wheezing

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Respiratory muscle testing

Measure maximum inspiratory P. (PImax, MIP) or negative inspiratory force (NIF)Maximum inhale via pressure manometerpNormal < -60 cmH2OUseful for evaluation neuromuscular dis:Useful for evaluation neuromuscular dis: myasthenia grevis, Guillian-Barre syndrome, diaphragmatic paralysis pre extubationdiaphragmatic paralysis, pre-extubationOther parameter: FVC, PEFR

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ClinicalClinical Applicationspp

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Case #1Case #1

Case #1

Parameter Actual %PredictedFVC (L) 4.11 116

FEV1 (L) 3.28 108

FEV1/FVC (%) 80 93

FEF (L/s) 6 94 88

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FEF25-75% (L/s) 6.94 88

PEFR (L/s) 3.15 107

C #2Case #2

Parameter Actual (best) Predicted %PredictedFVC (L) 4.31 4.44 97

FEV1 (L) 2.15 3.83 56

FEV1/FVC (%) 50 86 58

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FEF25-75% (L/s) 0.93 4.27 22

PEFR (L/s) 5.23 8.01 65

C #3Case #3

Parameter Actual (best) Predicted %PredictedFVC (L) 1.24 3.60 34

1 19 3 09 38FEV1 (L) 1.19 3.09 38

FEV1/FVC (%) 95.65 86.00 111

FEF (L/s) 1 69 3 48 48

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FEF25-75% (L/s) 1.69 3.48 48

PEFR (L/s) 4.37 6.70 65

Case #4

Parameter Actual (best) Predicted %PredictedFVC (L) 3.40 4.93 69

FEV (L) 2 17 4 25 51FEV1 (L) 2.17 4.25 51

FEV1/FVC (%) 63.72 84.68 75

FEF (L/s) 1.09 4.75 23

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FEF25-75% (L/s) 1.09 4.75 23

PEFR (L/s) 6.65 9.00 73

Case #5Case #5

Parameter Pre %Pred Post %Pred %Change

FVC (L) 1.58 84 1.91 102 21.07

FEV1 (L) 1.04 63 1.44 87 38.62

FEV1/FVC 66.05 77 75.63 88 14.50

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FEF25-75% 0.55 27 1.10 55 101.64

PEFR (L/s) 2.39 73 3.42 104 42.85