PULMONARY

FUNCTION TEST (PFT)

 Objectives
• Briefly review pulmonary anatomy and physiology
• Review lung volumes and capacities
• Provide an overview of pulmonary function tests
• Discuss spirometry and review its clinical applications
 Anatomy
• Lungs comprised of
– Airways
– Alveoli

http://www.aduk.org.uk/gfx/lungs.jpg
 The Airways
• Conducting zone: no gas
exchange occurs
– Anatomic dead space
• Transitional zone: alveoli
appear, but are not great
in number
• Respiratory zone: contain
the alveolar sacs

Weibel ER: Morphometry of the Human

Lung. Berlin and New York: Springer-
Verlag, 1963
 The Alveoli
• Approximately 300
million alveoli
• 1/3 mm diameter
• Total surface area if
they were complete
spheres 85 sq. meters
(size of a tennis court)

Murray & Nadel: Textbook of Respiratory

Medicine, 3rd ed., Copyright © 2000 W. B.
Saunders Company
 Mechanics of Breathing
• Inspiration
– Active process
• Expiration
– Quiet breathing: passive
– Can become active
 Pulmonary Function Tests
• Evaluates 1 or more major aspects of the
respiratory system
– Lung volumes
– Airway function
– Gas exchange
 Indications
• Detect disease
• Evaluate extent and monitor course of disease
• Evaluate treatment
• Measure effects of exposures
• Assess risk for surgical procedures
 Pulmonary Function Tests
• Airway function • Lung volumes and ventilation
– Simple spirometry – Functional residual capacity
– Forced vital capacity maneuver – Total lung capacity, residual volume
– Maximal voluntary ventilation – Minute ventilation, alveolar
– Maximal inspiratory/expiratory ventilation, dead space
pressures – Distribution of ventilation
– Airway resistance
 Pulmonary Function Tests
• Diffusing capacity tests • Cardiopulmonary exercise tests
• Blood gases and gas exchange • Metabolic measurements
tests – Resting energy expenditure
– Blood gas analysis – Substrate utilization
– Pulse oximetry • Chemical analysis of exhaled
breath
 Spirometry
• Measurement of the pattern of air movement into and out of
the lungs during controlled ventilatory maneuvers.
• Often done as a maximal expiratory maneuver
 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
 Lung Factors Affecting Spirometry
• Mechanical properties
• Resistive elements
 Mechanical Properties
• Compliance
– Describes the stiffness of the lungs
– Change in volume over the change in 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
 Resistive Properties
• Determined by airway caliber
• Affected by
– Lung volume
– Bronchial smooth muscles
– Airway collapsibility
 Factors That Affect Lung Volumes
• Age
• Sex
• Height
• Weight
• Race
• Disease
 Technique
• Have patient seated comfortably
• Closed-circuit technique
– Place nose clip on
– Have patient breathe on mouthpiece
– Have patient take a deep breath as fast as possible
– Blow out as hard as they can until you tell them to stop
Terminology
• 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
– Measured in liters (L)
 FVC
• Interpretation of % predicted:
– 80-120% Normal
– 70-79% Mild reduction
– 50%-69% Moderate reduction
– <50% Severe reduction

FVC
Terminology
• Forced expiratory volume in
1 second: (FEV1)
– Volume of air forcefully
expired from full inflation
(TLC) in the first second
– Measured in liters (L)
– Normal people can exhale
more than 75-80% of their
FVC in the first second; thus
the FEV1/FVC can be utilized
to characterize lung disease
 FORCED EXPIRATORY VOLUME - FEV1
• AMOUNT OF VOLUME • Interpretation of % predicted:
– >75% Normal
EXPIRED FORCEFULLY IN ONE – 60%-75% Mild obstruction
MINUTE – 50-59% Moderate obstruction
– <49% Severe obstruction

FEV1 FVC
Terminology
• Forced expiratory flow 25-75%
(FEF25-75)
– Mean forced expiratory flow during the
middle half of FVC
– Measured in L/sec
– May reflect effort-independent
expiration and the status of the small
airways
– Highly variable
– Depends heavily on FVC
 FEF25-75
• Interpretation of % predicted:
– >60% Normal
– 40-60% Mild obstruction
– 20-40% Moderate obstruction
– <10% Severe obstruction
 Criteria to perform the test
• Good start of test
• No coughing
• No variable flow
• No early termination
• Reproducibility
 Flow-Volume Loop

• Illustrates maximum expiratory

and inspiratory flow-volume
curves
• Useful to help characterize
disease states (e.g. obstructive
vs. restrictive)

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

2003
 Categories of Disease
• Obstructive
• Restrictive
• Mixed
Obstructive Disorders
• Characterized by a
limitation of expiratory
airflow
– Examples: asthma,
COPD
• Decreased: FEV1, FEF25-
75, FEV1/FVC ratio (<0.8)

• Increased or Normal:
TLC
Spirometry in Obstructive Disease
• Slow rise in upstroke
• May not reach plateau
Restrictive Lung Disease
• Characterized by diminished lung volume due
to:
– change in alteration in lung parenchyma
(interstitial lung disease)
– disease of pleura, chest wall (e.g.
scoliosis), or neuromuscular apparatus
(e.g. muscular dystrophy)
• Decreased TLC, FVC
• Normal or increased: FEV1/FVC ratio
Restrictive Disease

• Rapid upstroke as in normal

spirometry
• Plateau volume is low
Large Airway Obstruction
• Characterized by a
truncated inspiratory
or expiratory loop
 Other Lung Volumes
• Measured through various methods
– DLCO
– helium, 100% oxygen
– Body plethysmography
Changes in Lung Volumes in Various Disease States

Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003
 HOW TO INTERPRET PFT
• Check for FVC and FEV1 values ( If < 80% then it comes
under abnormal PFT i.e. can be obstructive or restrictive
or mixed disease)
• OBSTRUCTIVE DISEASE: BOTH FVC AND FEV1 ARE
REDUCED
ALONG WITH FEV1/FVC RATIO IS REDUCED
(NORMAL FEV1/FVC RATIO IS 75 TO 80%)
• RESTRCTIVE DISEASE: BOTH FVC AND FEV1 ARE
REDUCED
• FEV1/FVC RATIO IS HIGH
Clinical Applications
Case #1
Case #2
Case #3
Case #4
Case #5