7. Measurements
Abbreviation Characteristic measured
FEV1 Forced expired volume in 1 second
FVC Forced vital capacity
FEV1 /FVC Ratio Ratio of the above
PEFR Peak expiratory flow rate
FEF 25-75% Forced expiratory flow between 25-75% of the
vital capacity
11. Volume Time Curve
The vertical scale
indicates total volume (l)
the patient has blown out
The horizontal scale
indicates the total time (s)
the patient has been
blowing out for
Note the initial part of the
curve which is steep
followed by a gradual
flattening of the curve
13. Spirometry
FEF 25-75%: mean
forced expiratory flow
during middle half of
FVC; sensitive to small
airways disease
14. There is a lot of data reported
out on a PFT test
The only numbers to be really concerned
with are:
– FVC
– FEV1
– FVC / FEV1 ratio
– FEF25-75%
15. PFT Reports
o When performing PFT’s three values are reported:
o Actual – what the patient performed
o Predicted – what the patient should have
performed based on Age, Height, Sex, Weight,
and Ethnicity
o % Predicted – a comparison of the actual value
to the predicted value
16. PFT Reports
Example
Actual Predicted %Predicted
VC 4.0 5.0 80%
17. To calculate % predicted
Actual Measurement x100
Predicted Value
– e.g. Actual FEV1 = 4.0 litres
Predicted FEV1 = 4.0 litres
4 x 100 = 100%
4
18. To calculate the ratio of FEV1 to FVC
(FEV1%, FEV1/FVC or FER)
Actual FEV1 x100
Actual FVC
e.g. FEV1 = 3.0 litres
FVC = 4.0 litres
3 x100 =75%
4
19. ● Only need to look at 5 numbers
● Look at the post bronchodilator values too!
FEV1
% Predicted
FVC % Predicted
FER
(FEV1 / FVC ratio)
20. Spirogram Patterns
Normal
Obstructive
Restrictive
Mixed Obstructive and Restrictive
24. Mixed Obstructive and Restrictive
Volume, liters
Obstructive - Restrictive
Time, seconds
Normal
FEV1 = 0.5L
FVC = 1.5L
FEV1/FVC = 0.30
1. Restrictive and mixed obstructive-restrictive are difficult to diagnose by
spirometry alone; full respiratory function tests are usually required
25. Spirometry: Abnormal Patterns
Obstructive Restrictive Mixed
Time Time Time
Volume
Volume
Volume
Slow rise, reduced
volume expired;
prolonged time to
full expiration
Fast rise to plateau
at reduced
maximum volume
Slow rise to reduced
maximum volume;
measure static lung
volumes and full
PFT’s to confirm
28. Criteria for Normal
Post-bronchodilator Spirometry
FEV1: % predicted > 80%
FVC: % predicted > 80%
FEV1/FVC: > 0.7 - 0.8, depending on
age
29. Obstructive Pattern
● Decreased FEV1 < 80% predicted
● FVC can be normal or reduced – usually to
a lesser degree than FEV1
● Decreased FEV1/FVC
- <70% predicted
● FEV1 used to grade the severity
30.
31. SPIROMETRY
Before/After Bronchodilator
– An FEV1% less than predicted is a good
indication for bronchodilator study
– In most patients, an FEV1% less than 70%
indicates obstruction
32. SPIROMETRY
Before/After Bronchodilator
– Spirometry is performed before and after
bronchodilator administration to
determine the reversibility of airway
obstruction
33. Testing for reversibility in patients with
obstructive airways disease
Asthma and chronic obstructive pulmonary
disease (COPD) have many similarities and can
occur together in the same patient
The major difference between the two is that
airflow obstruction is largely reversible in asthma,
but in COPD it is largely irreversible.
33
34. 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
35. Bronchodilator Reversibility Testing
Can be done on first visit if no diagnosis has been
made
Best done as a planned procedure: pre- and post-bronchodilator
tests require a minimum of 15 minutes
Post-bronchodilator only saves time but does not
help confirm if asthma is present
Short-acting bronchodilators need to be withheld for
at least 4 hours prior to test
36. Bronchodilator Reversibility Testing
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
37. Patient preparation
To withhold or not to withhold medication?
If you are doing reversibility testing:
No short acting bronchodilators for 6 hours
No long acting bronchodilators for 12 hours
No sustained release oral bronchodilators
for 24 hours
38. Bronchodilator Reversibility Testing
Bronchodilator* Dose FEV1 before
and after
Salbutamol 200 – 400 μg via large
volume spacer
15 minutes
Terbutaline 500 μg via Turbohaler® 15 minutes
Ipratropium 160 μg** via spacer 45 minutes
* Some guidelines suggest nebulised bronchodilators can be given but the
doses are not standardised. “There is no consensus on the drug, dose or
mode of administering a bronchodilator in the laboratory.” Ref: ATS/ERS
Task Force : Interpretive strategies for Lung Function Tests ERJ 2005
** Usually 8 puffs of 20 μg
39. Inhaled or systemic steroids do not interfere with the
test results, and so, they do not need to be stopped.
Normal subjects can also respond to bronchodilators
by as much as 8% increase in FVC and FEV 1 , but this
change is not considered significant.
The definition of a significant response to
bronchodilators according to ATS & ERS is increase in
FEV 1 or FVC by >12% and >200 ml in the
postbronchodilator study
39
40. Bronchodilator Reversibility Testing
● FEV1 should be measured (minimum twice, within
5% or 150mls) 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
41. Bronchodilator Reversibility Testing
● Possible dosage protocols:
400 μg β2-agonist, or
80-160 μg anticholinergic, or
the two combined
● FEV1 should be measured again:
15 minutes after a short-acting β2-agonist
45 minutes after the combination
42. Bronchodilator Reversibility Testing
Results
● 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
43. SPIROMETRY
Before/After Bronchodilator
– Percentage of change is calculated
%Change = Postdrug – Predrug X 100
Predrug
44. SPIROMETRY
Before/After Bronchodilator
– FEV1 is the most commonly used test for
quantifying bronchodilator response
– Considered significant if:
FEV1 or FVC increase ≥12% and ≥ 200 ml
– FEV1% should not be used to judge
bronchodilation response
47. …Continued
Steroid reversibility testing:
- a steroid trial of PO 30 mg Prednisolone
daily for 2 weeks or
- 200 mcg Beclometasone or equivalent
inhaled corticosteroid for (6-8 weeks) is
undertaken.
48. Reversibility criteria
1. VC (forced or slow) and FEV1 the primary indices
for bronchodilator response.
2. A 12% increase, and a 200-ml increase in either
FVC or FEV1
3. FEF25-75 should be used secondarily in evaluating
bronchodilator response.
4. Ratios such as FEV1/VC should not be used to
judge bronchodilator response.
49. Often both FEV1 and FVC improve and the
FEV1/FVC ratio does not change.
Occasionally there is a significant improvement
in FVC with no change in FEV1 and the FEV1/FVC
ratio appears to get smaller. Therefore the
FEV1/FVC ratio should not be used to assess the
response to bronchodilators.
49
Reversibility criteria
50. The reversibility of airflow obstruction is often
demonstrated by repeating spirometry after
treatment.
Most often, a dose of inhaled beta-agonist (such as
salbutamol 2.5 mg by nebuliser) is administered after
the initial test and spirometry is repeated 15–30
minutes later.
Other bronchodilators, such as ipratropium bromide,
may also be used.
50
51. Alternatively, spirometry can be repeated after a
few weeks of inhaled or oral corticosteroid
treatment.
It is important to ensure that bronchodilators
have not been taken before the initial test.
51
52. Spirometric Diagnosis of COPD
COPD is confirmed by post–bronchodilator
FEV1/FVC < 0.7
● Post-bronchodilator FEV1/FVC measured 15
minutes after e
– 4 puffs Salbutamol 100 MDI with AeroChamber
– Salbutamol 2.5mg nebuliser
quivalent
53. Spirometric Diagnosis of COPD
Based on % Predicted of FEV1
Good predictor of Prognosis
Poor Predictor of Disability and Quality of Life
Categories;
BTS (1997)
GOLD (2001)
NICE (2004)
NICE (2010)
54. Severity of Obstruction
NICE
Guideline
(2004)
ATS/ERS
(2004)
GOLD (2008) NICE
Guideline
(2010)
Post-
Bronchodilat
or FEV1/FVC
FEV1 %
Predicted
Severity of Airflow Obstruction
Post -
Bronchodilator
Post -
Bronchodilator
Post -
Bronchodilator
<0.7 ≥ 80% Mild Stage 1-Mild Stage 1-Mild*
<0.7 50-79% Mild Moderate Stage 2-
Moderate
Stage 2-
Moderate
<0.7 30-49% Moderate Severe Stage 3-
Severe
Stage 3-
Severe
<0.7 < 30% Severe Very Severe Stage 4-Very
Severe**
Stage 4-Very
Severe**
*Symptoms should be present to diagnose COPD with mild airflow obstruction
**or FEV1 <50% with respiratory failure
59. The EPR3 recommends that office-based physicians
who care for asthma patients should have access to
spirometry, which is useful in both diagnosis and
periodic monitoring.
You would not consider managing hypertension
without a sphygmomanometer,or diabetes without a
glucometer
Accurate and objective assessment &
management of asthma is not possible without a
spirometer or peak flow meter
59
Spirometry for Asthma Diagnosis
60. Asthma & Spirometry: Diagnosis
Reversible airway obstruction –
a key feature of asthma
Spirometry –potential “proof”
of disease
Normal baseline spirometry does
not rule out asthma
60
61. Spirometry is an essential objective measure
to establish the diagnosis of asthma
Objective assessments of pulmonary function are
necessary for the diagnosis of asthma because
medical history and physical examination are not
reliable means of excluding other diagnoses or of
characterizing the status of lung impairment.
61
62. Patients with asthma frequently have poor
recognition of their symptoms and poor
perception of symptom severity, especially
if their asthma is long-standing.
Assessment of symptoms such dyspnea and
wheezing by physicians may also be
inaccurate.
62
63. Although physicians generally seem able to
identify a lung abnormality as obstructive (they
have a poor ability to assess the degree of
airflow obstruction)or to predict whether the
obstruction is reversible.
Pulmonary function measures often do not
correlate directly with symptoms.
63
64. Spirometry can demonstrate obstruction and
assess reversibility in patients 5 years of age.
Spirometry is generally recommended, rather
than measurements by a peak flow meter, due to
wide variability in peak flow meters and
reference values.
Peak flow meters are designed for monitoring,
not as diagnostic tools.
64
65. Spirometry
Hallmark of Asthma: Reversibility!
> 12% increase in FEV1.0 and ≥ 200 ml
after ß-2 inhalation
66.
67. FEV1 post-bronchodilator
FEV1 pre-bronchodilator
1
1
2
2
3
3
After bronchodilator
Before bronchodilator
4
4
5 6
Time (seconds)
FVC
Exhaled volume (L)
68. Typical Spirometric Tracing
1
2 3 4 5
Time (sec)
FEV1
Volume
Normal Subject
Asthmatic (After Bronchodilator)
Asthmatic (Before Bronchodilator)
Note: Each FEV1 curve represents the highest of three repeat measurements
69. Types of Flow
Volume Curves
Normal Obstructive
Liters per second
Concavity
Concavity
pre-bronchodilator
Improved
post-bronchodilator
Asthma
70. Spirometry is the recommended method of measuring
airflow limitation and reversibility to establish a
diagnosis of asthma.
Measurements of FEV1 and FVC are undertaken during
a forced expiratory maneuver using a spirometer.
The degree of reversibility in FEV1 which indicates a
diagnosis of asthma is generally accepted as ≥ 12%
and ≥ 200 ml from the pre-bronchodilator value.
70
71. However most asthma patients will not exhibit
reversibility at each assessment, particularly
those on treatment, and the test therefore lacks
sensitivity.
In severe cases, the FVC also may be reduced
due to trapping of air in the lungs
Repeated testing at different visits is advised.
71
72. Because many lung diseases may result in
reduced FEV1, a useful assessment of airflow
limitation is the ratio of FEV1 to FVC.
The FEV1/FVC ratio is normally greater than 0.75
to 0.80, and possibly greater than 0.90 in children.
Any values less than these suggest airflow
limitation.
72
73. Reversibility is a characteristic feature of asthma.
A significant improvement in spirometry may
suggest the diagnosis of asthma even if the
original measurements were within the
‘normal’ range.
However, in chronic asthma there may be only
partial reversibility of the airflow obstruction.
73
74. The airflow obstruction in chronic obstructive
pulmonary disease is largely irreversible. However, a
small but significant improvement in FEV1 can be
shown in many chronic obstructive pulmonary
disease patients.
Thus it may not be possible to distinguish between
chronic obstructive pulmonary disease and chronic
asthma on reversibility criteria alone. The results
should be interpreted in the clinical context.
74
75. Reversibility is sometimes used to guide treatment.
A large response to a bronchodilator indicates that
there is a potential to improve airflow obstruction.
This may justify a trial of anti-asthma medication
(such as inhaled corticosteroid) in patients
otherwise thought to have chronic obstructive
pulmonary disease.
75
76. A lack of response to a bronchodilator during
reversibility testing does not necessarily mean that the
bronchodilator will not provide important symptomatic
benefits such as an improvement in exercise tolerance.
The definition of significant reversibility requires that a
large percentage change is needed in patients with
severe airways disease.
For example an improvement in FEV1 from 0.6 litres to
0.75 litres (150 mL) would not be regarded as
‘significant’ because it could be due to measurement
error, even though a real change of this magnitude may
be a big improvement for the patient.
76
78. PEFR Variability
PEFmax - PEFmin
(pm, post-bd) - (am, pre-bd) X 100
PEFave
Asthma Diagnostic Clues:
• PEF Variability > 20%
(basis: home monitoring
2-4x/day for 1-2 weeks)
• Improvement in baseline PEF
by 20% after a 2-week
therapeutic trial
350
300
250
200
150
100
50
0
1 2 3 4 5 6 7
Days
PEFR (L/min)
pm PEFR
am PEFR
79.
80. Variability refers to improvement or deterioration in
symptoms and lung function occurring over time.
Variability may be experienced over the course of
one day (when it is called diurnal variability), from
day to day, from month to month, or seasonally.
Obtaining a history of variability is an essential
component of the diagnosis of asthma. In addition,
variability forms part of the assessment of asthma
control.
80
81. Measurement of lung function provides an
assessment of the severity of airflow
limitation, its reversibility and its variability,
and provides confirmation of the diagnosis
of asthma.
81
82. The terms reversibility and variability refer to changes
airflow limitation occur spontaneously or in response
to treatment.
The term reversibility is generally applied to rapid
improvement in symptoms accompanied by changes
in FEV1 (or PEF), measured within minutes after
inhalation of a rapid-acting bronchodilator—for
example after 200-400 ug salbutamol (albuterol)—or
more sustained improvement over days or weeks
after the introduction of effective controller treatment
such as inhaled corticosteroids.
82
83. Measurements of lung function, particularly the
reversibility of lung function abnormalities, provide a
direct assessment of airflow limitation.
Measuring the variability in lung function provides an
indirect assessment of airway hyperresponsiveness.
Measurements of the severity airflow limitation, its
reversibility and its variability are considered critical
in establishing a clear diagnosis of asthma
83
84. Classifying Asthma Severity:
BASED ON SYMPTOMS & LUNG FUNCTION
Daytime
Symptoms
Exacerbations Night
attacks
1
2
3
4
Intermittent <1x a week • Brief
Mild
persistent
>1x a week
but < 1x/day
• May affect
activity &
sleep
Moderate
persistent
Daily • May affect
activity &
sleep
Severe
persistent
•< 2x a
month
•> 2x a
month
•> once
a week
Daily • Frequent •Frequent
• Limits
physical
activity
FEV1 or PEF
•> 80% predicted
Variability <20%
•> 80% predicted
Variability 20 -30%
•> 60-80% predicted
Variability > 30%
•< 60% predicted
Variability > 30%
85. 85
Special Conditions
– In mild (or early) airway obstruction, the classic
reduction in FEV1 and FEV1/FVC ratio may not
be seen.
– The morphology of the FV curve can give a
clue, as the distal upward concavity may show
to be more pronounced and prolonged
– Another clue is the prolonged FET evident in
the VT curve
86. Asthma & Spirometry:Management
Severity class at diagnosis (FEV1%
pred)
Monitoring control (FEV1% personal
best)
Detection of significant dysfunction
in asymptomatic patients
Recommended yearly
86
87. Additional pulmonary function studies will help
if there are questions about COPD (diffusing
capacity), a restrictive defect (measures of lung
volumes), or VCD (evaluation of inspiratory flow-volume
loops).
Bronchoprovocation with methacholine, histamine,
cold air, or exercise challenge may be useful
when asthma is suspected and spirometry is
normal or near normal.
87
88. For safety reasons, bronchoprovocation should
be carried out only by a trained individual.
A positive test is diagnostic for airway hyperre
sponsiveness, which is a characteristic feature
of asthma but can also be present in other
conditions.
Thus, a positive test is consistent with asthma, but
a negative test may be more helpful to rule out
asthma.
88
90. SUMMARY OF LUNG FUNCTION PATTERNS
Parameter Obstructive Restrictive
PEFR Normal
FEV1
FVC Normal in asthma
Reduced in COPD
FEV1/FVC% <75% >75%
Gas transfer (TLCO) in Emphysema
Normal in Asthma
FEV1 response to
2-agonist > 12% in asthma No
response
< 12% in COPD
91. PEFR - Pros and Cons
Advantages
– With in 1 to 2 minutes,
– Inexpensive (meter costs less than Rs.1000)
– Simple, useful for frequent follow up use
Disadvantages
– Very much effort dependent
– Insensitive to small changes
– Small airways cannot be assessed
– Large inter & intra subject variation;↓accurate
92. Spirometry - Pros and Cons
Advantages
– Evaluates smaller as well as larger airways
– Relatively easy to use and maintain
– Reversibility can be tested with IBD and steroids
– Diagnostic as well as management assessments
Disadvantages
– Costs about 50,000 + computer and printer
– Takes time to perform – 10 to 15 minutes
– Requires training – at least one day course
93. Limitations to Spirometry
Effort dependant
– If patient can’t or won’t follow instructions, the quality
of results are poor and interpretation difficult
Doesn’t exclude asthma if spirometry is normal
Normal Spirometry doesn’t mean there is no
problem
– eg. Pulmonary vascular disease: Normal spirometry
but reduced TLCO (Transfer factor for carbon monoxide)
May be a prelude to further investigations
94. Bronchodilator reversibility testing
Although the values that show reversibility
are arbitrary, an increase of >400 ml from
baseline in FEV1 is suggestive of asthma.
Smaller increases are less discriminatory.
(Some texts suggest 200mls.)
95. History Suggests
COPD and
FEV1 < 80% predicted
FEV1/FVC < 70%
If in doubt
Bronchodilator
Reversibility
400 mcg Salbutamol or
equivalent Terbutaline
If FEV1 improves
> 400 mls
Asthma likely to be
present
Diagnose COPD
And follow COPD
guidelines
If still
In doubt
Steroid
reversibility
Oral Prednisolone
30 mg daily for
2 weeks
If FEV1 improves
> 400 mls
If no
doubt
If FEV1
improves
< 400 mls
If FEV1
improves
< 400 mls
96. Diagnostic Flow Diagram for Obstruction
Obstructive Defect
Is FVC Low? (<80% pred)
Combined Obstruction &
Restriction /or Hyperinflation
No Yes
Pure Obstruction
Improved FVC with
ß-agonist
Reversible Obstruction
with ß-agonist
Further Testing with
Full PFT’s
Suspect
Asthma
Suspect
COPD
Is FEV1 / FVC Ratio Low? (<70%)
Yes
Yes No
Yes No
Adapted from Lowry.
97.
98.
99. Restrictive Pattern
FEV1: Normal or mildly reduced
FVC: < 80% predicted
FEV1/FVC: Normal or increased > 0.7
100. Vital capacity is reduced in both
obstructive and restrictive diseases
VC
RV
VC
RV
VC
RV
Obstructive Normal Restrictive
101. Vital capacity is reduced in both
obstructive and restrictive diseases
IRV
TV
ERV
RV
VC
FRC
Normal
IRV
TV
ERV
RV
VC
FRC
Restrictive
IRV
TV
ERV
RV
VC
FRC
Obstructive
125
100
75
50
25
0
% Normal TLC
102. Forced Vital Capacity
TLC
FEV1.0 FVC
1 sec
FEV1.0 = 4 L
FVC = 5 L
% = 80%
RV
Normal
TLC
FEV1.0
FVC
1 sec
FEV1.0 = 1.2 L
FVC = 3.0 L
% = 40%
RV
Obstructive
airway resist
Restrictive
lung recoil
TLC
FEV1.0
FVC
1 sec
FEV1.0 = 2.7 L
FVC = 3.0 L
% = 90%
RV
103. Indication for lung volume test :
● Low FVC :
-? Restrictive
-? Obstructive with hyperinflation and air
trapping
-? Mixed pattern
-? Equivocal spirometry findings (FEV1&FVC at
lower limit of normal)
104. Be cautious about diagnosing a restrictive
disorder on spirometry alone, particularly if the
FEV1 is in the normal range.
Clinical correlation is necessary and more
detailed lung function tests are indicated.
Ideally, measurement of the total lung capacity
(TLC) should be used to confirm the diagnosis
10
4
105. Measuring TLC
To measure TLC or FRC, which include RV,
spirometry is insufficient
Techniques:
– Gas dilution
– Plethysmography (body box)
106. Diagnostic Flow Diagram for Restriction
Is FVC Low?(<80% pred)
Yes No
Restrictive Defect Normal Spirometry
Further Testing with
Full PFT’s; consider
referral if moderate to
severe
Is FEV1 / FVC Ratio Low? (<70%)
No
Adapted from Lowry, 1998
110. Classifying Abnormal Ventilatory
Function
1. A reduction of FEV1 in relation to the forced
vital capacity will result in a low FEV1/FVC and
is typical of obstructive ventilatory defects (e.g.
asthma and emphysema).
The lower limit of normal for FEV1/FVC is
around 70-75% but the exact limit is
dependent on age.
11
0
112. 2. The FEV1/FVC ratio remains normal or high
(typically > 80%) with a reduction in both FEV1
and FVC in restrictive ventilatory defects (e.g.
interstitial lung disease, respiratory muscle
weakness, and thoracic cage deformities such
as kypho-scoliosis).
11
2
113. In obstructive lung disease the FVC may be less
than the slow VC because of earlier airway
closure during the force manoeuvre. This may
lead to an overestimation of the FEV1/FVC.
Thus, the FEV1/VC may be a more sensitive
index of airflow obstruction.
11
3
114. Expiratory Relaxed Vital Capacity
Performed due to collapsing alveoli in some patients
during Forced Vital Capacity technique
This technique would usually be performed before the
Forced Vital Capacity readings
The reading is sometimes referred to as VC, EVC or RVC
Minimum of three readings taken -Two best results
should be within 150mls of each other
Maximum of 4 tests
115. Forced Vital Capacity (FVC)
A minimum of three readings should be taken
There should be less than 5% or 150mls variance
between the best two results
The technique should be repeated until this is
achieved or the patient is exhausted and can no
longer perform the technique
Time should be given to the patient to recover
between readings
116. 3. A reduced FVC together with a low FEV1/FVC
ratio is a feature of a mixed ventilatory defect in
which a combination of both obstruction and
restriction appear to be present, or
alternatively may occur in airflow obstruction as
a consequence of airway closure resulting in gas
trapping, rather than as a result of small lungs.
It is necessary to measure the patient's total lung
capacity to distinguish between these two
11 possibilities.
6
117. A forced vital capacity maneuver
Vol
(L)
0 1 2 3 4 5
Time (sec)
118. A forced vital capacity maneuver
Vol
(L)
0 1 2 3 4 5
Time (sec)
119. A forced vital capacity maneuver
Vol
(L)
0 1 2 3 4 5
Time (sec)
120. A forced vital capacity maneuver
Vol
(L)
0 1 2 3 4 5
Time (sec)
121. A forced vital capacity maneuver
Vol
(L)
0 1 2 3 4 5
Time (sec)
FVC
122. A forced vital capacity maneuver
Vol
(L)
0 1 2 3 4 5
Time (sec)
FEV1
123. A forced vital capacity maneuver
Vol
(L)
FEF25-75%
0 1 2 3 4 5
Time (sec)
124. A forced vital capacity maneuver
Vol
(L)
0 1 2 3 4 5
Time (sec)
FEV1
FEF25-75%
FVC
127. The Expiratory Flow–Volume Curve
(FV Curve)
Is determined by plotting FVC as flow (in liters
per second) against volume (in liters)
This curve is more informative and easier to
interpret, as different diseases produce distinct
curve shapes.
12
7
128. FlowVolume Curve
The vertical scale indicates
litres of air breathed out
per second (L/s) at that
moment in time
The horizontal scale
indicates the total volume
expired (L)
Note the sharp peak at the
beginning of the curve
followed by an initially
sharp trough that gradually
flattens out
129. 12
9
The Expiratory Flow–Volume Curve
(FV Curve)
130. The curve starts at full inspiration (at the total
lung capacity or TLC :the total amount of air in
the lungs at maximal inhalation with 0 flow (just
before the patient starts exhaling), then the flow
or speed of the exhaled air increases and
rapidly reaches its maximum, which is the PEF.
13
0
FlowVolume Curve
131. The curve then starts sloping down in an almost
linear way until just before reaching the volume
axis when it curves less steeply giving a small
upward concavity.
The curve then ends in that way at the residual
volume or RV by touching the volume axis, i.e.,
a flow of 0 when no more air can be exhaled
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FlowVolume Curve
132. There is no time axis in this curve, and the only
way to determine the FEV 1 is by the reading
device making a 1st second mark on the curve,
which is normally located at ~ 80% of the FVC.
Other data can be extracted from this curve
including FEF 25, 50, 75
The flow volume curve demonstrating the effort-dependent
and the effort independent parts.
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134. FEF 25–75 cannot be determined from this curve.
Instantaneous FEFs are directly determined from
the curve by dividing the FVC into four quarters
and getting the corresponding flow for the first,
second, and third quarters representing FEF
25,50,75 , respectively
The FEFs represent the slope of the FV curve .
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FlowVolume Curve
135. FlowVolume Curve
In summary, every part of the curve represents
something
– The leftmost end of the curve represents TLC.
– The curve’s rightmost end represents RV.
– Its width represents FVC.
– Its height represents PEF.
– The distance from TLC to the 1-s mark represents FEV1
– The descending slope reflects the FEFs.
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136. Remember that we cannot measure RV and
hence TLC with spirometry alone, because we
cannot measure the air remaining in the lung
after a full exhalation with this method.
The morphology of the curve is as important as
the other values.It provides information about the
quality of the study as well as being able to
recognize certain disease states from its shape.
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138. The Maximal Flow–Volume Loop
Combining the expiratory flow–volume curve,
with the inspiratory curve (that measures the IVC)
produces the maximal flow–volume loop, with
the expiratory curve forming the upper and the
inspiratory curve forming the lower parts of that
loop
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142. Normal appearance of a flow-volume
loop.
A flow-volume loop is generated by having the
patient inhale deeply to total lung capacity (TLC),
forcefully exhale until the lungs have been emptied
to residual volume (RV), and rapidly inhale to reach
TLC.
Flow is plotted on the Y axis and the volume on the
X axis; a typical loop .
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144. The maximal flow–volume loop, commonly includes a
tidal flow–volume loop too, shown in the center of the
maximal flow–volume loop as a small circle; This loop
represents quiet breathing.
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148. The Maximal Flow–Volume Loop
The maximal flow–volume loop, is even more
informative than the expiratory flow–volume
curve alone, as it also provides information about
the inspiratory portion of the breathing cycle.
For example, extrathoracic upper airway
obstruction, which occurs during inspiration, can
now be detected.
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159. Severe Obstructive Lung Disease
Curve descends more quickly than
normal and takes on a concave
shape, reflected by a marked
decrease in the FEF25-75.
With more severe disease, the peak
becomes sharper and the
expiratory flow rate drops
precipitously.
164. Spirometry interpretation
Ratio FEV1/IVC > 70%
FEV1 > 80% of predicted
Typical triangel shape
Linear decrease of flow
until FVC is reached
Upper point of inflection acute-angled
Nearly vertical
ascent
Exhalation (FVC) and
Inspiration (IVC) nearly identical
Normal Case
165. Differentiation between Restriction and Obstruction!
Restriction
Reduction of volumes
Tiffeneau-Index
FEV1/IVC > 70%
Obstruction
Reduction of flows
Tiffeneau-Index
FEV1/IVC < 70%
narrowing
of airways
VC
contraction of
alveolar tissue
FEV1
166. Spirometry interpretation
Mild obstructive:
- Ratio FEV1/IVC < 70%
- FEV1 > 70% of predicted
Peak-flow mostly diminished.
Expiratory flow/volume loop is
concavely shaped.
Vital capacity VC is mostly
normal.
E.g.: Asthma or COPD
168. Spirometry interpretation
Moderate to server Case
- Ratio FEV1/IVC < 70%
- FEV1 50% to 70% (moderate)
- FEV1 < 50% (severe)
Peak-flow diminished.
In case of dynamic
hyperinflation also VC is
reduced.
E.g.: Exacerbation of asthma,
severe COPD
170. Spirometry interpretation
Severe obstructive Case
- Ratio FEV1%IVC < 70%
- FEV1 dramatically decreased
- FVC, IVC usually decreased
Typical expiratory „Knickkurve“
As result of an airway collapse at
expiration
Often in severe emphysema
In severe obstruction
172. Spirometry interpretation
Restrictive Case
- FEV1%IVC > 70%
- FVC lower 80%
- Appearance of a narrowed
normal curve
- Decrease of FVC is characteristic
- Flows may be reduced
Becausse of increased tissue
tension it is possible that
FEV1%IVC values exceed the
normal range
175. How is a flow-volume loop
helpful?
1. In addition to obstructive and restrictive patterns,
flow-volume loops can show provide information
on upper airway obstruction:
1. Fixed obstruction: constant airflow limitation on
inspiration and expiration—such as in tumor, tracheal
stenosis
2. Variable extrathoracic obstruction: limitation of
inspiratory flow, flattened inspiratory loop—such as in
vocal cord dysfunction
3. Variable intrathoracic obstruction: flattening of
expiratory limb; as in malignancy or tracheomalacia
177. Spirometry interpretation
Intrathoracic Case
- FEV1 diminished
- IVC usually normal
Typical for the variable
extrathoracic stenosis is the
criation of an expiratory plateau
During expiration the obstruction
aggravates because the thoracic
pressure compresses the airways
and therefore narrows the
stenosis
179. Spirometry interpretation
Extrathoracic Case
- FEV1 may be > 80%
- IVC usually normal
The expiration is less obstructed
because the positive pressure inside
the airways dilates the stenosis.
Typical for a varible extrathoracic
stenosis is the plateau during
inspiration. During inspiration the
obstruction aggravates because the
negative pressure inside the airways
narrows the stenosis.
184. Upper Airway Obstruction
1. Fixed Obstruction
• Geometry and cross-sectional area of the
lesion do not change with the respiratory
cycle, so both inspiration and expiration are
affected equally
• Example: tracheal stenosis, bilateral vocal
cord paralysis, goiter
185. A fixed lesion may be extrathoracic or
intrathoracic.
Its presence results in similar flattening of both
the inspiratory and expiratory portions of the
flow-volume loop
Its causes include postintubation strictures,
goiters, and tracheal tumors
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186. Fixed Obstruction of the Upper Airway
The fixed obstruction limits flow
equally during inspiration and
expiration, and FEF = FIF.
Top and bottom of the loop are
flattened so that the configuration
approaches that of a rectangle.
Examples include tracheal stenosis,
bilateral vocal cord paralysis, and
goiter.
187. Upper Airway Obstruction
2. Variable Obstruction – configuration of the obstructive
lesion changes with the phases of respiration
Intrathoracic – lesion located below the sternal notch, so the
expiratory limb of the flow-volume loop is predominately
affected
•Example: tracheomalacia, neoplasm, Wegner’s
granulomatosis
Extrathoracic – lesion located above the sternal notch, so the
inspiratory limb of the flow-volume loop is predominately
affected
•Example: vocal cord paralysis
189. Variable extrathoracic obstruction
Schematic representation of an extrathoracic variable obstruction. The solid lines
represent actual curves, while the dashed line represents a normal inspiratory
pattern. Note that with the extrathoracic variable obstruction, exhalation induces a
positive intratracheal pressure, which in turn results in little or not resistance to flow
past the narrowed segment (top figure).
Conversely, inhalation generates negative intrathoracic pressure, which in turn
induces negative pressure in the trachea below the point of obstruction. This
negative pressure will induce further obstruction and increase resistance to flow.
190. During forced expiration, tracheal pressure
exceeds atmospheric pressure. The
obstruction is passively blown aside, and
expiratory flow is unimpaired. Conversely,
during forced inspiration, intratracheal pressure
becomes less than atmospheric pressure. The
obstruction is drawn inward, resulting in a
plateau of decreased inspiratory flow. Thus,
FIF<VFEaF. r Aina ebxalmepl eE isx vtorcaal ctohrdo parraalycsisi.c
Obstruction
192. Variable intrathoracic obstruction
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Schematic representation of an intrathoriacic variable obstruction. The solid
lines represent actual flow-volume curves, while the dashed line represents
the normal expiratory pattern. During exhalation, the transthoracic positive
pressure is transmitted to the intrathoracic narrowed segment, which results
in an increased resistance to flow (top figure).
Conversely, during inhalation, the negative intrathoracic pressure will distend
the narrowed segment, resulting in little or no resistance to flow
193. During a forced inspiration, negative pleural
pressure holds the "floppy" trachea open.
With forced expiration, pleural pressures
reach and then exceed intratracheal
pressures, and the loss of structural support
results in narrowing of the trachea and a
plateau of diminished flow. A brief period
of maintained flow is seen before airway
compression occurs. An example is
tracheomalacia.
Variable Intrathoracic
Obstruction
196. Indices of UAO
● FEV1 (ml) / PEF (L / m) = > 8 (Empey’s index)
FEF50/FIF50 (ratio of flow at 50% of
expiration and flow at 50% of inspiration)
FEF50 / FIF50 = <0.3 or > 1
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197. Indices further help confirm presence
and identify the type
of UAO.
Presence of UAO is indicated by Empey’s
index>/=8.
Type is determined by:
1. FEF50/FIF50 =1 in fixed UAO
2. FEF50/FIF50 >1 in variable extrathoracic upper
airway obstruction
3. FEF50/FIF50 < 0.3 in variable intrathoracic
19 upper airway obstruction
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198. Differentiates between obstruction that is
extrathoracic versus obstruction that is intrathoracic ?
Comparisons of the flow rate at the 50% point of
forced expiration (FEF50%) with the flow rate at the
50% point of forced inspiration (FIF50%)
FEF50%/FIF50% > 1 indicates extrathoracic (upper
airway) obstruction.
FEF50%/FIF50% < 1 indicates intrathoracic (tracheal
or bronchial) obstruction.
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