1. What exactly are PFTs?
• The term encompasses a wide variety of objective
methods to assess lung function. (Remember that the
primary function is gas exchange).
• Examples include:
– Spirometry
– Pulse oximetry
– Blood gases
– Lung volumes by helium dilution or body plethysmography
– Exercise tests
– Diffusing capacity
– Bronchial challenge testing
2. 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
3. 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
5. Indications
• Detect disease
• Evaluate extent and monitor course of
disease
• Evaluate treatment
• Measure effects of exposures
• Assess risk for surgical procedures
6. contraindications
• Chest or abdominal pain of any cause
• Oral or facial pain exacerbated by
mouthpiece
• Stress incontinence
• Dementia or confused state
• Within one month of Myocardial Infarction
7. To be avoided
• Smoking- 1 hour
• Alcohol- 4 hour
• Vigorous exercise -30 minutes
• Large meal – 2 hour
• Wearing tight clothes
8. Preparation
• Tests should be performed when patients are
clinically stable and free from respiratory infection
• Patients should not have taken:
inhaled short-acting bronchodilators in the
previous six hours
long-acting bronchodilator in the previous 12
hours
sustained-release theophylline in the previous
24 hours
13. 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
15. Lung Volumes
• 4 Volumes
• 4 Capacities
IRV – Sum of 2 or
IC
more lung
VC
TV volumes
TLC
ERV
FRC
RV RV
16. Tidal Volume (TV)
• Volume of air
inspired and
expired during
IRV normal quiet
IC
VC
breathing
TV
TLC
ERV
FRC
RV RV
17. Inspiratory Reserve Volume (IRV)
• The maximum
amount of air
that can be
IRV inhaled after a
IC
VC
normal tidal
TV
TLC volume
inspiration
ERV
FRC
RV RV
18. Expiratory Reserve Volume (ERV)
• Maximum
amount of air
that can be
IRV exhaled from
IC
VC
the resting
TV
TLC expiratory level
ERV
FRC
RV RV
19. Residual Volume (RV)
• Volume of air
remaining in the
lungs at the end
IRV of maximum
IC
VC
expiration
TV
TLC
ERV
FRC
RV RV
20. Vital Capacity (VC)
• Volume of air that
can be exhaled
from the lungs
IRV after a maximum
IC inspiration
VC
TV • FVC: when VC
TLC
exhaled forcefully
ERV
• SVC: when VC is
FRC
exhaled slowly
RV RV
• VC = IRV + TV +
ERV
22. 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)
23. FVC
• Interpretation of % predicted:
– 80-120% Normal
– 70-79% Mild reduction
– 50%-69% Moderate reduction
– <50% Severe reduction
FVC
24. 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
25. FEV1
• Interpretation of % predicted:
– >75% Normal
– 60%-75% Mild obstruction
– 50-59% Moderate obstruction
– <49% Severe obstruction
FEV1 FVC
26. Terminology
• Forced expiratory flow 25-
75% (FEF25-75)
– Mean forced expiratory flow
during 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
27. FEF25-75
• Interpretation of % predicted:
– >60% Normal
– 40-60% Mild obstruction
– 20-40% Moderate obstruction
– <10% Severe obstruction
28. Standard Spirometric Indicies
• FEV1 - Forced expiratory volume in one second:
The volume of air expired in the first second of
the blow
• FVC - Forced vital capacity:
The total volume of air that can be forcibly
exhaled in one breath
• FEV1/FVC ratio:
The fraction of air exhaled in the first second
relative to the total volume exhaled
32. Flow Volume Curve
• Standard on most desk-top spirometers
• Adds more information than volume
time curve
• Less understood but not too difficult to
interpret
• Better at demonstrating mild airflow
obstruction
34. 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
40. Flow Volume Curve Patterns
Obstructive and Restrictive
Obstructive Severe obstructive Restrictive
Expiratory flow rate
Expiratory flow rate
Expiratory flow rate
Volume (L) Volume (L) Volume (L)
Reduced peak flow, Steeple pattern, Normal shape,
scooped out mid- reduced peak flow, normal peak flow,
curve rapid fall off reduced volume
41. Bronchodilator Reversibility Testing
• Provides the best achievable FEV1
(and FVC)
• Helps to differentiate COPD from
asthma
Must be interpreted with clinical
history - neither asthma nor COPD
are diagnosed on spirometry alone
42. Bronchodilator Reversibility
Testing in COPD
Spirometry
•FEV1 should be measured (minimum twice,
within 5%) before a bronchodilator is given
•The bronchodilator should be given by
metered dose inhaler through a spacer device
or by nebulizer to be certain it has been
inhaled
•The bronchodilator dose should be selected to
be high on the dose/response curve
43. Bronchodilator Reversibility Testing
in COPD
•An increase in FEV1 that is both greater
than 200 ml and 12% above the pre-
bronchodilator FEV1 (baseline value) is
considered significant
•It is usually helpful to report the absolute
change (in ml) as well as the % change from
baseline to set the improvement in a clinical
context
48. Flow Volume Curve Patterns
Obstructive and Restrictive
Obstructive Severe obstructive Restrictive
Expiratory flow rate
Expiratory flow rate
Expiratory flow rate
Volume (L) Volume (L) Volume (L)
Reduced peak flow, Steeple pattern, Normal shape,
scooped out mid- reduced peak flow, normal peak flow,
curve rapid fall off reduced volume
49. Mixed Obstructive and Restrictive
Normal
Volume, liters
FEV1 = 0.5L
Obstructive - Restrictive FVC = 1.5L
FEV1/FVC = 0.30
Time, seconds
Restrictive and mixed obstructive-restrictive are difficult to diagnose by
spirometry alone; full respiratory function tests are usually required
(e.g., body plethysmography, etc)
50. Spirometry - Quality Control
• Most common cause of inconsistent
readings is poor patient technique
Sub-optimal inspiration
Sub-maximal expiratory effort
Delay in forced expiration
Shortened expiratory time
Air leak around the mouthpiece
• Subjects must be observed and
encouraged throughout the procedure
52. Unacceptable Trace - Poor Effort
Volume, liters
Normal
Variable expiratory effort
Inadequate sustaining of effort
May be accompanied by a slow start
Time, seconds
57. EXAMPLE 1
TEST PREDICTE BROCHODILATOR CHANGE
D
BEFORE AFTER
FVC 4.0 L 3.2 3.2
FVC%(O/P) 80% 80%
FEV1 3.7L 2.9 2.9 +0%- 0ml
FEV1%(O/P) 78% 78%
FEV1/FVC% 90% 90%
PEF 3.51L/S 4.22L/S
58. EXAMPLE -2
TEST PREDICTE BROCHODILATOR CHANGE
D
BEFORE AFTER
FVC 2.8L 0.6
FVC%(O/P) 22%
FEV1 2.75L 0.5
FEV1%(O/P) 18.18%
FEV1/FVC% 84%
PEF 5.3L/S 1.6
59. EXAMPLE 2 cont
TEST PREDICTE BROCHODILATOR CHANGE
D
BEFORE AFTER
FVC 2.8L 0.6 1.6L
FVC%(O/P) 22% 57%
FEV1 2.75L 0.5 1.0L +100%-500ml
FEV1%(O/P) 18.18% 36.3%
FEV1/FVC% 84% 63%
PEF 5.3L/S 1.6 4.8
60. EXAMPLE 3
TEST PREDICTE BROCHODILATOR CHANGE
D
BEFORE AFTER
FVC 2.60L 1.60 1.63
FVC%(O/P) 62% 63%
FEV1 2.17L 1.32 1.34 1.5%-20ml
FEV1%(O/P) 61% 62%
FEV1/FVC% 83% 82%
PEF 5.85L/S 5.34 4.56
61. EXAMPLE 4
TEST PREDICTE BROCHODILATOR CHANGE
D
BEFORE AFTER
FVC 2.3L 1.8 1.8
FVC%(O/P) 78% 78%
FEV1 1.95L 0.75 0.75 +0-0ml
FEV1%(O/P) 38% 38%
FEV1/FVC% 41% 41%
PEF 3.10L/s 1.30L/S 1.34L/S
62. EXAMPLE 5
TEST PREDICTE BROCHODILATOR CHANGE
D
BEFORE AFTER
FVC 3.22L 1.69 1.82
FVC%(O/P) 52% 56%
FEV1 2.50L 1.15 1.19 +3%
FEV1%(O/P) 46% 48%
FEV1/FVC% 68% 66%
PEF 7.17L/S 4.48 4.41
63. EXAMPLE 6
TEST PREDICTE BROCHODILATOR CHANGE
D
BEFORE AFTER
FVC 2.75L 1.1 1.5
FVC%(O/P) 40% 54%
FEV1 2L 0.9 1.0 +11%-100ml
FEV1%(O/P) 31% 46%
FEV1/FVC% 81% 66%
PEF 3.7L/s 1.00L/s 3.20L/s
64. EXAMPLE 7
TEST PREDICTE BROCHODILATOR CHANGE
D
BEFORE AFTER
FVC 3.2L 1.54 2.3
FVC%(O/P) 48% 71%
FEV1 2.75L 0.95 1.94 +104%-
990ml
FEV1%(O/P) 34.5% 72%
FEV1/FVC% 61% 69%
PEF 4.50L/s 3L/s 3.70L/s
65. EXAMPLE 8
TEST PREDICTE BROCHODILATOR CHANGE
D
BEFORE AFTER
FVC 3.2 L 2.55 2.75
FVC%(O/P) 79% 86%
FEV1 2.75L 1.95 2.3 +18%-
350ml
FEV1%(O/P) 70% 84%
FEV1/FVC% 76% 83%
PEF 4.5L/s 4.00L/s 4.40L/s
