Interpretation of PFT

2. Interpretation of
Pulmonary Function
Tests

3. The Perioperative Surgical Home
A patient-centered,
physician-led system of
coordinated care that guides
patients throughout the entire
surgical experience. From the
decision for surgery to
discharge from a medical
facility and beyond, the PSH
model of care is structured to
improve patient care and
outcomes.

4. PPCs are common and a major cause of overall
perioperative morbidity and mortality.
Even more often than cardiac complications.
The National Surgical Quality Improvement Program
(NSQIP) found that PPCs were the most costly of major
postoperative medical complications (including
cardiac, thromboembolic, and infectious) and resulted
in the longest length of hospital stay.
Postoperative
Pulmonary
Complications

5. Postoperative
Pulmonary
Complications
Atelectasis
Infection, including bronchitis and pneumonia
Prolonged mechanical ventilation and
respiratory failure
Exacerbation of underlying chronic lung
disease
Thromboembolic disease

7. The impact of PPCs has become increasingly
apparent,
Estimation of their risk should be a standard
element of all preoperative medical
evaluations.
This is increasingly driven by evidence-based
medicine, rather than expert opinion.

8. Anesthesiologists should balance the risks and costs
of these evaluations against their benefits.
• History and Clinical examination
• Preanesthesia Chest Radiographs
• Consultation with specialists
• Pulmonary function tests

9. Pulmonary function
tests

10. What Functions We Should Test?
• Airways
– Small
– Large
• Parenchyma
– Alveoli
– Interstisium
• Pulmonary Vasculature
• Bellows & Pump mechanism
– Diaphragm
– Chest wall
• Neural Control of Ventilation

11. Pulmonary function tests
Tests for Assessment of Mechanical Ventilatory
Functions of the Respiratory System:
• Dynamic Lung Volumes (Spirometry)
• Static Lung Volumes
• Respiratory Muscle Function
– Maximum inspiratory & expiratory pressures

12. Pulmonary function tests
Tests for Assessment of Gas Exchange:
• Diffusion Capacity DLCO
• Arterial blood gases
• Overnight oximetry

13. Pulmonary function tests
Tests for Assessment of Cardiopulmonary
Interaction:
• Cardiopulmonary exercise testing.
• 6-minute-walk test.
• Right Heart Catheterisation.

14. Goals of Preoperative PFT
Predict the likelihood of PPCs in lung resection surgery
or cardiac surgery.
Obtain quantitative baseline information concerning
pulmonary function that guides decision making, and
identify patients who may benefit from therapy
preoperatively.
Obtain baseline pulmonary function data so assessment
for liberation of MV and/or tracheal extubation might be
based on.

15. SPIROMETRY
• Spirometry is the
most commonly
used lung function
screening study.

16. • It’s role is well established in lung resection
or cardiac surgeries.
• Spirometry has NO effective risk prediction
value for PPCs.
• There are NO prohibitive threshold for
spirometric values below which the risk for
surgery would be unacceptable.
• Changes in clinical management due to
findings from preoperative spirometry were
not reported.
Perioperative Indications of Spirometry

17. Studies:
1. Routine preoperative spirometry: abnormal
findings in 15.0–51.7% of cases.
2. Indicated preoperative PFT’s were reported as
abnormal in 17.0–27.1% of cases, and
3. Indicated preoperative spirometry were
reported as abnormal in 33.1–45.0% of cases.

19. The authors reported that a predicted FEV1 of
less than 61%, and a PaO2 less than 70 mmHg
each were independent risk factors for PPCs.

20. 1. Maximal pressures generated in the thorax
impact on abdominal and thoracic
organs/tissues.
2. Large swings in blood pressure.
3. Expansion of the chest wall and lungs.
4. Active communicable diseases.

21. Myocardial infarction within the last month
Unstable angina
Recent thoraco-abdominal surgery
Recent ophthalmic surgery
Thoracic or abdominal aneurysm
Current pneumothorax

22. SPIROMETRY

23. Modern Spirometry

24. SpiroSmart

27. The main spirometry tests are:
FVC (Forced Vital Capacity)
VC (Vital Capacity or Slow Vital Capacity)
MVV (Maximum Voluntary Ventilation)
SPIROMETRY

28. FVCForced Vital Capacity
Tidal breathing
The patient starts with some tidal breathing.
Maximum inspiration
The patient fills his lungs entirely (TLC). No need to be forced but must be
as deep as possible.
Forced expiration
Immediately after, the patient performs a maximal expiration as fast, as
hard and as long as he can.
Forced inspiration
Immediately after, a second inspiration is performed as forced and as
quickly as possible.

30. (Slow) Vital Capacity
Inspiratory Vital Capacity: The patient inspires fully and than
slowly expires all the air in his lungs
Expiratory Vital Capacity: the other way around: the patient
expires fully and inspires slowly to a maximum
This test used to be performed to get VC and to be able to calculate the
FEV1/VC ratio (FEV1% or Tiffeneau index).

31. (Slow) Vital Capacity
The expiratory SVC > FVC
In patients with obstructive small airways disease &
a collapse of the small airways is suspected
Inspiratory VC = Expiratory SVC
= Expiratory FVC

32. Two graphs:
Volume-time curve
The flow-volume loop
SPIROGRAM

33. Volume-Time Tracing and Flow-Volume Loop
Identify the anatomic
location of airflow
obstruction
Ascertain the
technical
adequacy of a
manoeuvre
They provide important graphic and numeric data regarding the
mechanical properties of the lungs.

34. Volume Time Graph
A healthy subject will
expire between 70
and 90% of the FVC
in the first second of
the test.
It takes roughly
about 5 sec to expire
the last 10-30 % of
the FVC.

35. Numeric Data
Volume parameters:
These parameters represent volumes and can be read
from the volume-time graph:
• FVC
• FEV1
• FEV.5
• FEV3
• FEV6
• FEV1/FVC ratio (FEV1%)
• FEV3/FVC ratio (FEV3%)
• FEV1/FEV6 ratio (FEV6%)

36. FVC
FVC is a measure of lung volume.
• Restrictive disorders: ↓↓ FVC
(pulmonary fibrosis, kyphoscoliosis,
neuromuscular disease, and pleural effusion).
• Pseudorestriction: ↓↓ FVC with hyperinflated lungs
(due to severe airflow obstruction and air trapping, as in
emphysema.)

37. Forced Expiratory Volume in 1 Second
• Reflects mechanical
properties of the large and
the medium-sized airways
• It is reduced in obstructive
and restrictive disorders
• In normal persons, the FEV1 accounts for the greatest part (80%)
of the exhaled volume from a spirometric manoeuvre

38. • FEV1%=FEV1/VC X100
• FEV1%=FEV1/FVC X100
• FEV1%=FEV1/FEV6 X100
Nowadays the value is compared to LLN
Tiffeneau index

39. FEV1 FVC FEV1 %
Obstructive
Lung Disease
Normal
(very mild Obstruction)
Or
Decreased
(Mod./severe Obstruction)
Normal
(Mild/Mod. Obstruction)
Or
Decreased
(severe Obstruction)
Decreased
(<70%)
Restrictive
Lung Disease
Normal
Or
Decreased
Decreased Normal
Or
Increased
(≥ 70%)

40. The Flow-Volume
loop
• It is the most important
graph in spirometry
• The morphology tells
immediately if the test was
well done.

41. • Begins at ZERO volume & flow.
• The curve rapidly (150 msec) mounts to a
peak (PEF) = air expired from the large upper
airways (trachea-bronchi).
• The curve descends (=the flow decreases)
FEF25 FEF50 FEF75
• FEF2575: The mean flow between the points
FEF25 and FEF 75
• The flow reaches zero & the FVC is reached
No time axis on
the flow-volume loop

42. Maximal Mid-Expiratory Flow
(MMEF)
The maximal flow rates
between 25%-75% of the forced
vital capacity (FEF25-75%).
• These may provide
information regarding small
airway function.
• The lower limit of normal
falls significantly with
age.

43. FEV3/FVC ratio
• FEV3% is a new
parameter to assess
small airways function.
• FEF25–75 measurements can
be misleading (false-negative
results and false-positive
results).

44. Numeric Data
Flow parameters:
These parameters represent flows and can be read from
the flow-volume loop:
• PEF
• PIF
• PEF 2575
• PEF 25
• PEF 50
• PEF 75

46. Obstructive Lung
Disease

47. • The small airways are
partially obstructed
• FEV1 will be too low
• A normal FVC at the
early stages
• FEV1% < 70%
• FET (Forced Expiratory Time)
is prolonged

48. • The disease generally affects the
expiratory limb (Airflows that are
independent of effort is reduced)
• The descending limb of the
expiratory loop is typically
concave.
• FEF25-75 is low.
• The effort-dependent PEF may
be normal or reduced.

49. Bronchodilator Testing
• Following the administration of a bronchodilator such
as 2.5mg of nebulised salbutamol.
• A positive response: a 12% increase in FEV1
with an increase of 200mls or more.

50. • When the baseline spirogram is relatively normal. Bronchial
challenge testing may also be considered
• PC20FEV1: The provocative concentration dosage level of the
inhalational agent (methacholine) required to produce a 20%
reduction in the FEV1.
• PC20FEV1 < 8 mg/mL suggests clinically important
airway hyperreactivity
• GOOD –VE TEST

51. Restrictive Lung Disease

52. • ↓↓ FEV1
• ↓↓ FVC
• FEV1% is normal or
even elevated
• ↓↓ TLC
Restrictive Lung Disease

53. • The F/V loop is narrowed,
but the shape is generally
the same as in normal.
• Flow rates are greater than
normal at comparable lung
volumes because the increased
elastic recoil of lungs holds the
airways open.
Restrictive Lung Disease

56. Static Lung Volumes
• Spirometry is an expiratory maneuver.
• ↓↓ VC during spirometry should prompt measurement of
TLC to confirm the presence or absence of a true restrictive
ventilatory disorder.
• FRC is usually measured by:
1. A gas dilution technique.
2. Body plethysmography.
3. Imaging Techniques.

57. Residual Volume
Total Lung Capacity
Functional Residual
Capacity
↑↑ in patients with
obstructive defects such
as emphysema
↓↓ in patients with
restrictive abnormalities as
kyphoscoliosis.

58. Nitrogen washout or helium dilution.

59. Gas dilution techniques
• Measure of all air in the lungs
that communicates with the
airways.
• A limitation of this technique
is that it does not measure air in
non-communicating bullae,
and therefore it can
underestimate TLC,
especially in patients with
severe emphysema.

60. Whole body plethysmography
• The patient sits inside an
airtight box, inhales or
exhales to a particular volume,
and then a shutter drops across
their breathing tube. The subject
makes respiratory efforts against
the closed shutter.
• The changes in pressure in a
constant volume box or volume
in a constant pressure box is
measured.

61. • The primary advantage of body plethysmography is that it can
measure the total volume of air in the chest, including gas
trapped in bullae.
• Another advantage is that this test can be performed quickly.
Whole body plethysmography
• Drawbacks include the complexity of the equipment as
well as the need for a patient to sit in a small enclosed
space.

63. Diffusion Capacity - DLCO

64. Diffusion capacity (DLCO)
or transfer factor gives
important information
regarding the integrity and
size of:
Single breath technique:
• where 10% helium and 0.3%
carbon monoxide are rapidly
inspired,
• held for 10 seconds and
• then expired with
• The measurement of the
remaining carbon monoxide.
• Comparison of the inspired
and expired CO fractions
The alveolar
blood
membrane

65. Adjustments of DLCO
• Normally the value is corrected for the patient’s haemoglobin
(DLCOc).
• The transfer coefficient (KCO) is DLCOc corrected for alveolar
volume:
– DLCOc after pneumonectomy will be reduced but
– KCO will be normal

68. Interpretation

69. 1. Predicted values: spirometry values
are compared to the predicted values
that are calculated from age, gender,
ethnicity and height
2. Lower Limits of Normal (LLN): is the
lower fifth percentile of the Gaussian bell
curve. This also applies to the Tiffeneau
index.
3. Historical Data: healthy patients will
lose up to 25 mL of FEV1 every year from
the age of 25. A patient that has blown
120% of his predicted values and blows
100% of his predicted values one year
later may have a very big problem
Pathological
Spirometry

70. One should first make sure that the test was done
according to standard, before interpreting the results of
the test.
Quality Assessment of the
Spirogram
The volume-time tracing is most useful in assessing
whether the end-of-test criteria have been met,
whereas the F-V loop is most valuable in evaluating the
start-of-test criteria.

71. Good Quality Flow
volume loop:
Typical shape
inspiration & expiration
Quality Assessment of the Flow-Volume Loop

72. A frequent variation of the
normal flow-volume loop:
Shoulder in spirometry loops
from young females.
Quality Assessment of the Flow-Volume Loop

73. Reproducibility
To be sure that the patient has blown his
maximal values during the FVC spirometry
test, it is necessary to let him blow at least
twice.
Reproducibility is calculated on three
parameters:
1. FEV1
2. FVC
3. PEF
The patient will need to repeat the test
until he has blown two reproducible tests
or until he has tried 8 times.
Quality Assessment of the Flow-Volume Loop

74. 1. Couphing
The flow to suddenly fall
to zero and rise again
Quality Assessment of the Flow-Volume Loop
2. Expiration Too
Slow
The peak flow is not within
the first 100 milliseconds and
there is a dent in the loop
3. Patient hesitates
At the start of the loop
Common Errors

75. The technique of back-extrapolation of the start of the test
to establish a zero time point on the volume-time tracing.
It corrects for delayed or hesitant starts that might
otherwise be mistaken for a falsely reduced FEV1.
Quality Assessment of the Flow-Volume Loop

76. Incomplete Expiration
Quality Assessment of the Flow-Volume Loop
Larger Inspiration Than Expiration
The patient did not fill his lungs
completely before the test:
inspiration>expiration
A sudden drop at the right end
of the loop, the loop is 'cut off‘
FVC is underestimated.

78. Expiratory Time Not
Sufficient:
According to the ATS criteria
(American Thoracic Society)
expiratory time should be
equal to or exceed
6 seconds.
(3 seconds is set as a
minimum)
Quality Assessment of the Spirogram

81. Pulmonary function tests in patients
undergoing lung resection
The British Thoracic Society guidelines:
• Pneumonectomy can be considered with FEV1> 2.0 L
• Lobectomy if FEV1> 1.5 L in the absence of any interstitial lung
disease or unexpected disability due to shortness of breath.
As absolute values may be lower in older patients and women,
patients are generally considered suitable for resection if
FEV1> 80% predicted and DLCO > 80% predicted.

82. In case of borderline lung function
The post operative predicted FEV1 and DLCO
(calculated either with knowledge of the number of lung segments
to be resected or through quantitative lung perfusion scanning).
Patients with a post operative predicted FEV1 or DLCO < 40%
Patients undergoing lung resection
Are deemed at high risk of peri-operative
death and complications.

83. • CPET may be necessary for further risk stratification.
• Patients with PFTS below 30% predicted may potentially be
considered for lung transplantation assuming no other
contraindications are present.
Patients undergoing lung resection
• DLCO should be routinely measured during pre-operative
evaluation of lung resection candidates, regardless of
whether the spirometric evaluation is abnormal.

85. Large Airway Obstruction

86. • Tracheal stenosis, goiter
• The top and bottom of the
loops are flattened
(rectangle).
• Fixed obstruction limits flow
equally during inspiration and
expiration, and MEF = MIF.
Fixed obstruction of the upper airway

88. • Unilateral vocal cord
paralysis
• When a single vocal cord
is paralyzed, it moves
passively with pressure
gradients across the
glottis.
• Therefore, MIF < MEF

89. • Tracheomalacia
• During a forced inspiration,
negative pleural pressure holds
the “floppy” trachea open.
• With forced expiration, loss of
structural support results in
tracheal narrowing of the
trachea and a plateau of
diminished flow.
• Flow is maintained briefly before
airway compression occurs.

92. Pred. PRE %
FVC 5,7 5,01 88%
FEV1 4,75 4,26 90%
FEV1% 82,5 85%
FEF2575 5,19 4,46 86%
PEF 10,45 1,02 97%
FET 5sec
a. The test was not properly executed
b. Normal spirometry
c. Obstructive lung disease
d. Restrictive lung disease
e. Mixed lung disease
f. Upper airway obstruction

93. a. The test was not properly executed
b. Normal spirometry
c. Obstructive lung disease
d. Restrictive lung disease
e. Mixed lung disease
f. Upper airway obstruction
Pred. PRE %
FVC 5,44 5,39 99%
FEV1 4,57 4,20 92%
FEV1% 82,7 78%
FEF2575 5,14 4,47 87%
PEF 10,19 9,68 95%
FET 7sec

94. a. The test was not properly executed
b. Normal spirometry
c. Obstructive lung disease
d. Restrictive lung disease
e. Mixed lung disease
f. Upper airway obstruction
Pred. PRE %
FVC 5,12 5,17 101%
FEV1 4,23 3,68 87%
FEV1% 80,9 71%
FEF2575 4,69 3,09 66%
PEF 9,7 4,07 42%
FET 7sec

95. a. The test was not properly executed
b. Normal spirometry
c. Obstructive lung disease
d. Restrictive lung disease
e. Mixed lung disease
f. Upper airway obstruction
Pred. PRE %
FVC 3,47 3,48 100%
FEV1 3,07 3,14 102%
FEV1% 88,5 90,2%
FEF2575 4,17 3,84 92%
PEF 7,18 7,25 101%
FET 2,8sec

96. a. The test was not properly executed
b. Normal spirometry
c. Obstructive lung disease
d. Restrictive lung disease
e. Mixed lung disease
f. Upper airway obstruction
Pred. PRE %
FVC 5,49 5,55 101%
FEV1 4,61 3,32 72%
FEV1% 82,7 60
FEF2575 5,16 3,30 64%
PEF 10,25 10,34 101%
FET 12sec

97. a. The test was not properly executed
b. Normal spirometry
c. Obstructive lung disease
d. Restrictive lung disease
e. Mixed lung disease
f. Upper airway obstruction
Pred. PRE %
FVC 3,9 3,91 100%
FEV1 3,41 3,51 103%
FEV1% 84,4 89%
FEF2575 4,17 4,57 109%
PEF 7,38 6,8 92%
FET 5sec

98. a. The test was not properly executed
b. Normal spirometry
c. Obstructive lung disease
d. Restrictive lung disease
e. Mixed lung disease
f. Upper airway obstruction
Pred. PRE %
FVC 4,63 0,60 13%
FEV1 3,97 0,55 14%
FEV1% 82,7 92,6%
FEF2575 4,86 1,02 21%
PEF 9,33 2,99 32%
FET 3sec

99. a. The test was not properly executed
b. Normal spirometry
c. Obstructive lung disease
d. Restrictive lung disease
e. Mixed lung disease
f. Upper airway obstruction
Pred. PRE %
FVC 4,79 4,02 84%
FEV1 4,03 3,40 84%
FEV1% 82,7 84,6%
FEF2575 5,1 4,69 92%
PEF 10,07 8,67 86%
FET 7sec