Transcript Slide 1

Pulmonary Function Tests
Wanida Paoin
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Objectives
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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
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Air travels via laminar
flow through the
conducting airways:
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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
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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
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IRV
IC
VC
TV
4 Volumes
4 Capacities
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Sum of 2 or more
lung volumes
TLC
ERV
FRC
RV
RV
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Pulmonary Function Tests
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Pulse oximetry
Blood gases
End tidal CO2
Spirometry
Peak expiratory flow rate
Bronchial challenge testing
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Respiratory muscle pressure measurement
Lung volumes by helium dilution or body
plethysmography
Diffusing capacity
• Exercise tests
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Pulmonary Function Tests
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Evaluates 1 or more major aspects of
the respiratory system
• Lung volumes
• Airway function
• Gas exchange
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Indications
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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
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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
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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
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They do not act alone.
They act only to support
or exclude a diagnosis.
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Mechanical Properties
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Compliance
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Elastic recoil
• Describes the stiffness of the lungs
• volume / pressure
• The tendency of the lung to return to it’s
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resting state
A lung that is fully stretched has more elastic
recoil and thus larger maximal flows
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Resistive Properties
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Determined by airway caliber
Affected by
• Lung volume
• Bronchial smooth muscles
• Airway collapsibility
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Factors That Affect Lung Volumes
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Age
Sex
Height
Weight
Race
Disease
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Special Considerations
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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
PEFR
Spirogram
FVC
FEF25-75
FEV1
Flow-Volume Curve
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Technique
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Acceptable criteria
Give instructions and demonstrate
< 10 y: > 3 min
Patient performs the maneuver
> 10 y: > 6 min
or no more volume > 1 min
• Sit / Stand direct
Not inhale
• Puts nose clip on
No air leak
• Inhales maximally
pause
• Puts mouthpiece on mouth No
and closes
lips around
mouthpiece
2 maximum FVC different < 10%
• 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)
20 ATS, 1994)
(adapted from
FVC
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Forced vital capacity
(FVC):
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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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FEV1
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Forced expiratory
volume in 1 second:
(FEV1)
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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)
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FEF25-75
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Forced expiratory flow 2575% (FEF25-75)
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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
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PEFR
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PEFR
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Peak flow meter device
Technique
• Sit/Stand direct
• Inhales maximally
• Puts mouthpiece on mouth and closes lips around
mouthpiece
80%
• Blow out as hard and Green
fast as: >
possible
Yellow
: 50-79%
• Repeat minimum of three
times
: < 50%
< 20% /
• Use the best value forRed
interpretationNormal
as %predicted
Normal
personal
best< 12%
• Clinical application: monitor severity, daily variability,
pre and post bronchodilator
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Categories of Disease
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Obstructive
Restrictive
Mixed
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FVC
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Interpretation of % predicted:
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80 %
70-79%
50%-69%
<50%
Normal
Mild reduction
Moderate reduction
Severe reduction
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FEV1
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Interpretation of % predicted:
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>80%
65-79%
50-64%
<49%
Normal
Mild obstruction
Moderate obstruction
Severe obstruction
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Spirometry Interpretation:
FVC
FEV1
FEF25-75%
PEFR
FEV1/FVC
% predicted
> 80%
> 80%
> 70%
> 80%
> 80% absolute value
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Spirometry in Obstructive
Disease
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Slow rise in upstroke
May not reach
plateau
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Restrictive Disease
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Rapid upstroke
as in normal
spirometry
Plateau volume is
low
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Spirometry Interpretation: Obstructive vs.
Restrictive Defect
What parameter is the most sensitive in airway obstruction?
Parameter
Obstructive
Disorders
Restrictive
Disorders
FVC
N or ↓
↓
FEV1
↓
↓
FEF25-75%
↓
N to ↓
FEV1/FVC
↓
N or ↑
PEFR
↓
N to ↓
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Spirometry Interpretation:
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Obstructive Disorders
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Characterized by a
limitation of expiratory
airflow
Examples:
• Asthma
• Bronchiectasis
• COPD
• Cystic Fibrosis
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Restrictive Disorders
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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
PEFR
flow
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expiration
volume
inspiration
TLC
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RV
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.
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Restrictive Lung Disease
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Characterized by
diminished lung volume
Decreased TLC, FVC
Normal or increased:
FEV1/FVC ratio
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Obstructive Lung Disease
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Characterized by a
limitation of expiratory
airflow
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Examples: asthma,
COPD
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Large Airway Obstruction
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Characterized by a
truncated
inspiratory or
expiratory loop
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Flow-Volume Loops
L1
L2
L3
L4
R1
R2
R3
Incomplete exhalation
Variable extrathoracic ob
Variable intrathoracic ob
Fixed central or up aw ob
Inadq effort
Restrictive lung disease
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(Rudolph and Rudolph,
2003)
Spirometry: Pre and Post Bronchodilator
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Obtain spirogram and flow-volume loop.
Pre and 15 minutes after administration of
the bronchodilator
Salbutamol MDI 4 puffs via valve spacer
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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
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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
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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
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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
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
10744
Case #2
Parameter
Actual (best)
Predicted
%Predicted
FVC (L)
4.31
4.44
97
FEV1 (L)
2.15
3.83
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FEV1/FVC (%)
50
86
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FEF25-75% (L/s)
0.93
4.27
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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
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FEV1 (L)
1.19
3.09
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FEV1/FVC (%)
95.65
86.00
111
FEF25-75% (L/s)
1.69
3.48
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PEFR (L/s)
4.37
6.70
6546
Case #4
Parameter
Actual (best)
Predicted
%Predicted
FVC (L)
3.40
4.93
69
FEV1 (L)
2.17
4.25
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FEV1/FVC (%)
63.72
84.68
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FEF25-75% (L/s)
1.09
4.75
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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
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