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Pulmonary Function Tests

Wanida Paoin

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Objectives

Review basic pulmonary anatomy and lung volume.

Indication for PFTs. Technique and basic interpretation of

spirometry. Difference between obstructive and restrictive

lung disease. Clinically application

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Conducting Airways

Air travels via laminar flow through the conducting airways:• trachea,

• lobar bronchi,

• segmental bronchi,

• subsegmental bronchi,

• small bronchi,

• bronchioles, and

• terminal bronchioles.

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From Netter Atlas of Human Anatomy, 1989

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Gas Exchange

Capillaries are wrapped around alveoli.

Approximately 300 million alveoli

Alveolar-capillary barrier: 0.3 μm in some places, surface area of 50-100 square meters! (size of a tennis court)

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

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Lung Volumes

IRV

ERV

4 Volumes 4 Capacities

• Sum of 2 or more lung volumes

RV

IC

FRC

VC

TLC

RV

TV

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Pulmonary Function Tests

• Pulse oximetry • Blood gases • End tidal CO2

• Spirometry• Peak expiratory flow rate • Bronchial challenge testing

• Exercise tests • Respiratory muscle pressure measurement• Lung volumes by helium dilution or body

plethysmography• Diffusing capacity

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Pulmonary Function Tests

Evaluates 1 or more major aspects of the respiratory system• Lung volumes

• Airway function

• Gas exchange

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Indications

Detect disease Evaluate extent and monitor course of

disease Evaluate treatment Measure effects of exposures Assess risk for surgical procedures Assess bronchial hyperreactivity

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Evaluate extent and monitor course of disease

Obstructive disease - asthma - FB - subglottic, tracheal stenosis - tracheomalacia - vascular ring - vocal cord paralysis

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Evaluate extent and monitor course of disease

Restictive disease - external compression: thoracic cage abnormality, pleural effusion, pneumothorax, obesity, scoliosis - unexpanded lung: interstitial fibrosis, pulmonary edema - neuromuscular disease: poliomyelitis, myasthenia grevis

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Importance

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

Provides objective evidence in identifying patterns of disease

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Spirometry

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

Silhouette of Hutchinson Performing Spirometry, From Chest, 2002

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Limitation

They do not act alone. They act only to support

or 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’s

resting state

• A lung that is fully stretched has more elastic recoil and thus larger maximal flows

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Resistive Properties

Determined by airway caliber Affected by

• Lung volume

• Bronchial smooth muscles

• Airway collapsibility

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Factors That Affect Lung Volumes

Age Sex Height Weight Race Disease

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Special Considerations

Ability to perform spirometry dependent on developmental age of child, personality, and interest of the child.

Patients need a calm, relaxed environment and good coaching. Patience is key.

Even with the best of environments and coaching, a child may not be able to perform spirometry.

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Parameter from spirometer

Flow-Volume Curve

Spirogram

FVC

FEV1FEF25-75

PEFR

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Technique Give instructions and demonstrate Patient performs the maneuver

•Sit / Stand direct•Puts nose clip on• Inhales maximally•Puts mouthpiece on mouth and closes lips

around mouthpiece•Exhales as hard and fast and long as possible•Repeat minimum of three times (check for

reproducibility.)•Use the best value for interpretation as

%predicted of control (age, height, sex, race)

(adapted from ATS, 1994)

Acceptable criteria< 10 y: > 3 min > 10 y: > 6 minor no more volume > 1 minNot inhaleNo air leakNo pause

2 maximum FVC different < 10%

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FVC

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

be exhaled forcefully from TLC

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

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

expired from full inflation (TLC) in the first second

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

FEV1

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Forced expiratory flow 25-75% (FEF25-75)

• Mean forced expiratory flow during middle half of FVC

• May reflect effort independent expiration and the status of the small airways

• Highly variable

• Depends heavily on FVC

FEF25-75

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PEFR

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PEFR

Peak flow meter device Technique

•Sit/Stand direct• Inhales maximally•Puts mouthpiece on mouth and closes lips

around mouthpiece•Blow out as hard and fast as possible•Repeat minimum of three times •Use the best value for interpretation as

%predicted / personal best •Clinical application: monitor severity, daily

variability, pre and post bronchodilator

Green : > 80%Yellow : 50-79%Red : < 50%

Normal < 20%Normal <

12%

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Categories of Disease

Obstructive Restrictive Mixed

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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:

% predicted

FVC > 80%

FEV1 > 80%

FEF25-75% > 70%

PEFR > 80%

FEV1/FVC > 80% absolute value

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Spirometry in Obstructive Disease

Slow rise in upstroke May not reach

plateau

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Restrictive Disease

Rapid upstroke as in normal spirometry

Plateau volume is low

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Spirometry Interpretation: Obstructive vs. Restrictive Defect

Parameter Obstructive Disorders

Restrictive Disorders

FVC

FEV1

FEF25-75%

FEV1/FVC

PEFR

N or ↓ ↓

↓ ↓

↓ N to ↓

↓ N or ↑

↓ N to ↓

What parameter is the most sensitive in airway obstruction?

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Spirometry Interpretation: Obstructive Disorders

• Characterized by a limitation of expiratory airflow

Examples:

• Asthma

• Bronchiectasis

• COPD

• Cystic Fibrosis

Restrictive Disorders• Characterized by

reduced lung volumes/decreased lung compliance

Examples:

• Interstitial Fibrosis

• Kyphoscoliosis

• Obesity

• Lung Resection

• Neuromuscular diseases

• Cystic Fibrosis

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Flow-Volume Loop

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

Do FVC maneuver and then inhale as rapidly and as much as able.

The expiratory and inspiratory flow volume curves put together make a flow volume loop.RVTLC

PEFR

flow

volume

expiration

inspiration

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Restrictive Lung Disease

Characterized by diminished lung volume

Decreased TLC, FVC Normal or increased:

FEV1/FVC ratio

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Obstructive Lung Disease

Characterized by a limitation of expiratory airflow• Examples: asthma,

COPD

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Large Airway Obstruction

Characterized by a truncated inspiratory or expiratory loop

38(Rudolph and Rudolph, 2003)

Flow-Volume Loops

Variable intrathoracic obFixed central or up aw ob

Inadq effort

Incomplete exhalationVariable extrathoracic ob

Restrictive lung disease

L1

L2

L3

L4

R2

R3

R1

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Spirometry: Pre and Post Bronchodilator

Obtain spirogram and flow-volume loop. Pre and 15 minutes after administration of

the bronchodilator Salbutamol MDI 4 puffs via valve spacer

• Slow inhale

• Breath hold 5-10 sec.

• 5-10 sec pause between each puff. Reversibility: FEV1 / PEFR > 12% Improve flow-volume loop.

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PEFR

Inhales maximally Exhales as hard and fast and short as possible Repeat minimum of three times Use the best value for interpretation as

%predicted of control / personal best Highly effort dependent Diurnal variation (normal < 20%) Different value in each devices

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Exercise challenge test

Perform spirometry Exercise 6-8 min (tread mill) till HR

160-180/min Repeat spirometry at 5, 10, 15,

20, 30 min EIB: 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 manometer Normal < -60 cmH2O Useful for evaluation neuromuscular dis:

myasthenia grevis, Guillian-Barre syndrome, diaphragmatic paralysis, pre-extubation

Other parameter: FVC, PEFR

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Clinical Applications

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Case #1

Parameter Actual %Predicted

FVC (L) 4.11 116

FEV1 (L) 3.28 108

FEV1/FVC (%) 80 93

FEF25-75% (L/s) 6.94 88

PEFR (L/s) 3.15 107

Case #1

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Case #2

Parameter Actual (best) Predicted %Predicted

FVC (L) 4.31 4.44 97

FEV1 (L) 2.15 3.83 56

FEV1/FVC (%)

50 86 58

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

PEFR (L/s) 5.23 8.01 65

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Case #3

Parameter Actual (best) Predicted %Predicted

FVC (L) 1.24 3.60 34

FEV1 (L) 1.19 3.09 38

FEV1/FVC (%) 95.65 86.00 111

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

PEFR (L/s) 4.37 6.70 65

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Case #4

Parameter Actual (best) Predicted %Predicted

FVC (L) 3.40 4.93 69

FEV1 (L) 2.17 4.25 51

FEV1/FVC (%) 63.72 84.68 75

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

PEFR (L/s) 6.65 9.00 73

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Case #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

FEF25-75% 0.55 27 1.10 55 101.64

PEFR (L/s) 2.39 73 3.42 104 42.85