Spirometry Basics

Spirometry
“Spiro” – from the greek for breathing
“Metry” – measurement
“Spirometry” – The measurement of breathing

 Spirometry is a measure of air flow and lung
volumes during a forced expiratory manouver
from full inspiration
 Spirometry is a method of assessing lung function
by measuring the total volume of air the patient
can expel from the lungs after a maximal
inhalation.
5
What is a spirometry ??

What is Spirometry?
 Spirometry is the measure of:
How quickly the lung can be emptied and filled
AND
How much air can be blown out
 Spirometry measures How much and How quickly
air can be expelled following a deep breath .

Desktop Electronic Spirometers

Measuring vital capacity and
its subcomponents.
 Use a spirometer.
TLC
VC
RV
IC
FRC
IRV
ERV
RV
Can Use
Spiromenter
Can’t Use a Spirometer
TV

Lung Volume
 By calculation:
RV = TLC - VC
by spirometry
by body
plethysmography
TLC or helium dilution
FRC = TLC - IC

Measurement of Lung Volumes
Recall that spirometry can only measure volume from RV to
TLC. Volume below RV is not “seen” by spirometry.

Spirometer
 A spirometer measures the flow or rate at
which lung volume changes as a function of
time .
 A spirometer measures subdivisions of vital
capacity .
 A spirometer does NOT measure RV .

 A spirometer can be used to measure the
following:
– FVC and its derivatives (such as FEV1, FEF 25-
75%)
– Peak expiratory flow rate
– Maximum voluntary ventilation (MVV)
– Slow VC
– IC, IRV, and ERV
– Pre and post bronchodilator studies

Spirometric indices
 FVC (forced vital capacity)
 FEV1 (forced expiratory volume in 1 s)
 FEV1/FVC
 FEV6 (forced expiratory volume in 6 s)
 FEF25-75 (Maximum Mid Expiratory Flow)
 PEF (peak expiratory flow)
 MVV ( Maximal voluntary ventilation )

 VC–vital capacity (L)
 FVC–forced vital capacity (L)
 FEV1–one-second forced expiratory volume (L)
 FEV1/FVC
 FEF25-75%--forced expiratory flow (L/S)
 PEF–peak expiratory flow (L/S or L/min)
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Spirometric indices

Common Uses of PFTs
1. To evaluate respiratory symptoms
2. To determine severity of impairment and disability in
patients with known respiratory disease
3. To follow the course of disease in a patient, including
the response to therapy
4. To assess preoperative risk for predicting postoperative
respiratory complications
5. To screen for subclinical disease

Why Perform Spirometry?
 Diagnostic
– Causes of symptoms (eg. breathlessness)
Is breathlessness due to heart or lung disease?
– Assess pre-operative risk. Fit for surgery?
– Screen individuals at risk of lung disease (eg.
smokers)
– Measure severity of airway obstruction or restriction
– Demonstrates to the patient, the presence and
reversibility of airway obstruction. e.g. Asthma

 Objective Assessment
– The patients subjective assessment is often
misleading
– Helps differentiate organic and psychosomatic
disorders
– Provides objective feedback to the patient about the
presence and severity of respiratory defect

 Monitoring
– Assess response to bronchodilator therapy
– Determine the minimum effective dose of
preventative medication
– Tool used in the Asthma 3+ Plan

 Evaluations for Disability / Impairment
Assessment for:
– Rehabilitation program - capacity for work?
– Medico-legal reasons
– Insurance evaluation -risk?
– Fitness to dive

What can PFTs tell you about
the patient
 Normal or abnormal
 What diseases can you diagnose?
– Only asthma is defined by its PFTs
 Estimation of impairment, or severity of
disease
 Response to therapy
 Occupational surveillance

What PFTs cannot tell you
 Does the degree of abnormality explain the
patients symptoms?
 “Normality” does not exclude the presence
of disease
 Abnormal test may not reflect loss of lung
function

PFTs are really wonderful but…
 They do not act alone.
 They act only to support or exclude a diagnosis.
 A combination of a thorough history and physical
exam, as well as supporting laboratory data and
imaging will help establish a diagnosis.

Contraindications
 No absolute contraindications.
 FVC manoeuvre raise intra-cranial, intra-thoracic
and intra abdominal pressures so,
relative contraindications may be:
Recent eye, thoracic or abdominal surgery.
Recent Myocardial Infarction (Last 3 months)
Unstable cardiovascular status (uncontrolled
hypertension or pulmonary embolism ).

Contraindications
Recent cerebrovascular haemorrhage or
known cerebral or abdominal aneurysm.
Pneumothorax.
Haemoptysis of unknown origin (FVC maneuver
may aggravate underlying condition).
Acute disorders affecting test performance
(e.g. vomiting, nausea, vertigo).

Patient preparation
Before the test
Avoid:
 Acohol 4h
 Large meal 2h
 Smoking 1h
 Vigorous exercise 30 min
 Wear loose, comfortable clothing.
 Relaxed, and have time to visit the toilet.

 For bronchodilator reversibility testing
withhold bronchodilators prior to the test:
Short-acting inhaled B2 agonists for 12-24h.
Long-acting inhaled anticholinergics for 24-36 h.
Theophyllines for 12 h.
Sustained release theophyllines for 24 h.

Prior to Spirometry
 Gain verbal consent
 Check for contraindications and that the patient
has been properly prepared for the test
 Gain an accurate height
 Make note of Ethnic Origin and Age
 The room should be a comfortable temperature
 The patient should be sat in a hard backed chair
with their feet able to touch the floor

Prior to Spirometry
 The patient should sit upright with their legs
uncrossed
 A drink of water should be made available
 The technique and purpose of spirometry should
be explained in full prior to the test
 Spirometry should be performed in the patients
own time and they should not feel hurried
Reinforce and Reassure

Spirometry Maneuver
In single breath test
 A few normal tidal respirations
 Then deeeeep inspiration
 Momentary breath holding
 Very forced and fast expiration
– As hard and as fast as he/she can blow out
 Then deep, quick and full inspiration
 Repeat at least 3 times – take the best

American Thoracic Society (ATS)
Spirometry Guidelines
Minimum of 3 technically acceptable blows
(may need to perform up to 8 or more blows)
Rapid take-off with no hesitation, cough, leak,
tongue occlusion, glottic closure, early termination,
valsalva manoeuvre
Reproducible: within 200 ml from 2 of 3 technically
acceptable blows
Blow out for at least 6 seconds
A nose peg is encouraged
Prefer to have patient sitting

 Conventionally, a spirometer is a device used to
measure timed expired and inspired volumes,
and from these we can calculate how effectively
and how quickly the lungs can be emptied and
filled.
 Spirometry is usually recorded as either a
spirogram (a plot of volume versus time) or flow-volume
curve or loop (a plot of volume versus
flow).
35

Spirometric Curves
 The Volume–Time Curve (The Spirogram)
 The Expiratory Flow–Volume Curve (FV
Curve)
36

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

Volume-Time Spirogram
1)Tidal volume respirations
2) At end expiration,
patient performs maximal
inspiration to TLC, followed
by
3) Exhalation as hard and
as fast as possible until “all
the air is out”
•The volume of air
exhaled is the FVC
•The remaining volume of
air in the lungs is RV
Volume (L )
FVC
RV

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

 Basic spirometry involves only the measurement
of forced vital capacity (FVC) and the forced
expired volume in the first second (FEV1).
 The ratio between the two is a self-controlled
statistic which tells if obstruction is present.
 FVC and FEV1 can be measured against
predicted values.
46

 PEFR is not reproducible enough measurement
for accurate diagnosis, but may be used more
for following progress with asthma.
 FEF 25-75% is a measurement of smaller airway
function but this measurement is usually not
clinically useful
47

The Volume–Time Curve (The Spirogram)
49

 FVC is the highest point in the curve
 FEV 1 is plotted in the volume axis opposite to
the point in the curve corresponding to 1s
 Duration of the study (the forced expiratory time
or FET) can be determined from the time axis,
6 s in this curve.
50

51

 FEF 25,50,75 can be roughly determined by dividing
the volume axis into four quarters and determining the
corresponding time for each quarter from the time
axis.
 Dividing the volumes (a, b, and c) by the
corresponding time (A, B, and C) gives the value of
each FEF (FEF 25 , FEF 50 ,FEF 75 , respectively).
 Note that this method represents a rough
determination of FEFs, as FEFs are actually measured
instantaneously by the spirometer and not calculated.
52

53

 FEF 25–75 can be roughly determined by
dividing the volume during the middle half of
the FVC (c–a) by the corresponding time (C–A).
 FEF 25–75 represents the slope of the curve at
those two points .
54

 This curve also provides an idea about the
quality of the spirometry,as it shows the
duration of the exhalation [the forced
expiratory time (FET)], which needs to be at
least 6 s for the study to be clinically
reliable.
56

 Is simply the FVC plotted as volume in liters
against time in seconds
 You can extract from this curve both the FVC and
FEV1.
 FEV 1 /FVC ratio can be estimated by looking at
where the FEV 1 stands in relation to the FVC in
the volume axis
57

 If a post bronchodilator study is done, as in case
of suspected bronchial asthma, then there will
be two discrete curves.
 One curve will represent the initial prebronchodilator
study whereas the second will represent the post
bronchodilator study.
 Looking at how the two curves compare to each
other gives an idea about the degree of the
response to bronchodilator therapy, if any
59

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%

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

PFT Reports
 Example
Actual Predicted %Predicted
VC 4.0 5.0 80%

Spirometry : Percent Predicted
 Absolute values can be compared for one subject at
different times
 Percent predicted values allow comparison to
population norms based on:
– Sex
– Age
– Height
– Race** - typically Black, White, “Hispanic;”
everything else refers back to White values
– Weight
 Percent predicted also can be compared for one
subject over time, allows for growth

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)

65
Forced Vital Capacity (FVC)
 Following full inspiration, patient exhales as rapidly as
possible, forcibly and completely- volume of air
exhaled is measured; takes 5-6 seconds with majority
in 1 second.
 Volume obtained is expressed as a % of predicted
normal. Normals are based on volumes obtained
from thousands of healthy individuals of similar age,
sex, ht and wt and race.
 Normal 80% of predicted.

Forced Vital capacity (FVC)
 is the volume of gas expired when the forced
expiratory manoeuvre is continued to full
expiration.
 In most healthy persons this point is reached
within 6 s (hence FEV6), but in the presence of
airflow limitation from narrow or collapsible
airways the expiration can continue for much
longer (up to 15 s). In this circumstance the FEV6
is a poor guide to FVC.

Forced vital capacity
A measure of VOLUME
– How much air that can be forcefully exhaled
– Normally FVC = VC
 Varies directly with height and inversely
with age
 Reported in liters and % of predicted

FVC and SVC are compared with each other in a normal subject
( a ) and in a patient with an obstructive disorder ( b ). In case of airway
obstruction, SVC is larger than FVC, indicating air trapping
68

 In addition, due to dynamic compression
the FVC is then less than some other
estimates of vital capacity, including
inspiratory vital capacity (IVC)
69

Vital capacity: slow vital capacity or
forced vital capacity?
 In some patients with obstructive airways disease, the forced
vital capacity (FVC) will underestimate the true vital capacity
(VC). This is because the increase in intrathoracic pressure
during the forced manoeuvre compresses airways, causing
early airway closure and gas trapping. This does not happen
in normal lungs.
 If suspected, it can be detected by measuring the vital
capacity (from full inspiration to full expiration) without trying
to force the air out (sometimes called a slow or relaxed vital
capacity, SVC).
 Some pulmonary function equipment also allows the vital
capacity to be measured as an inspiratory manoeuvre
(inspiratory vital capacity, IVC).
70

Vital capacity is reduced in both
obstructive and restrictive diseases
VC
RV
VC
RV
VC
RV
Obstructive Normal Restrictive

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

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)

Measuring TLC
 To measure TLC or FRC, which include RV,
spirometry is insufficient
 Techniques:
– Gas dilution
– Plethysmography (body box)

Assessing severity of restrictive defects
 Without TLC measurement, base severity
on the FVC
– ≥80% is considered “normal”
– 70-80% is considered mild
– 60-70%% is considered moderate
– 60% is considered severe
 When TLC is measured
– Gold standard to define restrictive
ventilatory defect

FVC
 Interpretation of % predicted:
– 80-120% Normal
– 70 – 80 % Mild reduction
– 50% –70 % Moderate reduction
– <50% Severe reduction
FVC

FEV1 :
Volume of air which can be forcibly exhaled
from the lungs in the first second of a forced
expiratory maneuver.

Forced expiratory volume
in 1 second: (FEV1)
Volume of air forcefully
expired from full inflation
(TLC) in the first second
Normal people can
exhale more than 75-80%
of their FVC in the first
second
Measured in liters (L)

80
FEV1
 FEV1 :Amount of air forcibly exhaled in the 1st
second of the FVC maneuver (80% of FVC
volume).
 Volume obtained is expressed as a % of
predicted normal. Normals are based on
volumes obtained from thousands of healthy
individuals of similar age, sex, ht and wt and
race.
 Normal  80% of predicted.

5 10 15
8
6
4
2
Time (s)
Volume (L)
Normal spirogram:
Volume / time
Man
176 cm
76 kg
FVC
FEV1
0 1

Forced expiratory volume
in 1 second (FEV1)
A measure of FLOW
─ Reported in liters and % of predicted
─ 80 – 120% of predicted is a normal value

FEV1
 The FEV1 may be misleading if interpreted alone
as it can be low in the face of a low FVC
 Considered abnormal if < 80% of predicted value
 Dyspnea usually present if < 50% of predicted
value

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

Severity of any spirometric
abnormalities based on the FEV1
Degree of severity FEV1 % predicted
 Mild >70
 Moderate 60-69
 Mod severe 50-59
 Severe 35-49
 Very Severe < 35
based on ATS/ERS criteria

FEV1
― >75% Normal
― 60%-75% Mild obstruction
― 50-59% Moderate obstruction
― <49% Severe obstruction
FEV1 FVC

FEV1/FVC
• Forced expiratory
volume in 1 second
– 4.0 L
• Forced vital capacity
– 5.0 L
– usually less than during
a slower exhalation
• FEV1/FVC = 80%
FEV1
FVC

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

90
FEV1/FVC
 FEV1/FVC: Very important ratio; when reduced,
helps identify presence of obstructive disease.
 Percentage reduction correlates with severity
of obstruction; normal is 75-80%.
 Normal (or ) in patients with restrictive disease.

FEV1 / FVC ratio
 The FEV1/FVC ratio is the ratio of the forced expiratory
volume in the first one second to the forced vital
capacity of the lungs.
 The normal value for this ratio is above 75-80%,
though this is age dependent.
1. Values less than 70% are suggestive of airflow
limitation with an obstructive pattern
2. Restrictive lung diseases often produce a FEV1/FVC
ratio which is either normal or high
91

 FEV1 expressed as a percentage of the VC is the
standard index for assessing and quantifying
airflow limitation.
 FEV1%VC declines with age and height.
As IVC > EVC > FVC in patients with obstructive
lung disease, the VC should be specified when
using the FEV1/VC ratio, hence FEV1%FVC
(Forced Expiratory Ratio, FER) or FEV1%IVC.
The Tiffeneau-index is FEV1%IVC
92

FEV1% = (FEV1/FVC) × 100
 Forced expired volume in 1 second as percentage
of forced vital capacity.
 FEV1% is used as a guide to airway calibre and
has the merit that, unlike FEV1 it is nearly
independent of lung size, body size and stature.

FEV1% = (FEV1/FVC) × 100
 FEV1%may be misinterpreted if vital capacity is
affected by increased strength or weakness of the
accessory muscles of respiration or by dynamic
compression, or if residual volume varies semi-independently.
 Thus, a reduced FEV1% should not be interpreted as
evidence for airflow limitation unless FEV1 is itself
reduced.

Normal Values
 FEV1/FVC ratio is the percentage of FVC that
can be expired in one second.
– 75 – 80% is normal
– 60 – 80% demonstrates mild obstruction
– 50 – 60% demonstrates moderate obstruction
– <50% demonstrates severe obstruction

Normal Trace Showing FEV1 and FVC
5 FVC
FEV1 = 4L
FVC = 5L
FEV1/FVC = 0.8
1
2 3 4 5 6
4
3
2
1
Volume, liters
Time, seconds

Spirometry:
Obstructive Disease
Volume, liters
FEV1 = 1.8L
FVC = 3.2L
FEV1/FVC = 0.56
Time, seconds
5
4
3
2
1
1 2 3 4 5 6
Normal
Obstructive

Spirometry: Restrictive Disease
Volume, liters
Time, seconds
FEV1 = 1.9L
FVC = 2.0L
FEV1/FVC = 0.95
1 2 3 4 5 6
5
4
3
2
1
Normal
Restrictive

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
2. (e.g., body plethysmography, etc)

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

Classification Of Ventilatory Abnormalities
by Spirometry
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2

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

 FEF25-75% is the average expired flow over the
middle half of the FVC manoeuvre and is
regarded as a more sensitive measure of small
airways narrowing than FEV1.
 Unfortunately FEF25-75% has a wide range of
normality, is less reproducible than FEV1, and is
difficult to interpret if the VC (or FVC) is reduced
or increased.
10
4

Forced mid expiratory flow
(FEF25-75%)
 Sometimes termed the maximal mid expiratory
flow rate (MMEF)
A measure of FLOW
 Measures flow rate over the middle half of
expiration
 Should be reported as L/sec and as % of
predicted

Forced mid expiratory flow
(FEF25-75%)
 It is less effort dependent compared to the FEV1 /
FVC ratio
 It may detect closure of small airways better than
the FEV1 or FEV1 / FVC ratio
 Normal values vary widely
– Varies with age, ht, wt

FEF25-75
– >60% Normal
– 40-60% Mild obstruction
– 20-40% Moderate obstruction
– <10% Severe obstruction

MMEF25-75%
 Maximum Mid expiratory Flow rate
 Max. Flow rate during the mid-expiratory part of FVC
maneuver.
 Effort independent
– N value – 4.5-5 l/sec. Or 300 l/min
– It may detect closure (obstruction ) of small distal
airways better than the FEV1 or FEV1 / FVC ratio
– But if the FEV1 / FVC ratio is greater than about 75%
of predicted, the FEF25-75% is usually normal

 Forced expiratory flow (FEF25−75%fvc) was
formerly maximal mid expiratory flow (MMEF).
 This index is the average flow over the middle
half of the forced vital capacity during maximally
forced expiration
 It is used for detecting the early stages of airflow
limitation, but not for clinical management of
patients.

 MEFR – Mid-expiratory flow rates:
(FEF25−75%),
Derived from the mid portion of the flow
volume curve but is not useful for COPD
diagnosis
11
0

FEV6 – Forced expired volume in six seconds:
 Often approximates the FVC. FEV6 is the forced
expiratory volume during the first 6 seconds and
is a surrogate of the FVC.
 Easier to perform in older and COPD patients but
role in COPD diagnosis remains under
investigation
11
1

 FEV6 (the volume exhaled in the first 6 seconds) is
sometimes used as an alternative measurement
to the FVC if the spirometer is unable to record
beyond 6 seconds, or if the patient finds
prolonged expiratory manoeuvres exhausting.
 The FEV6 may underestimate the FVC in
obstructive disorders, but this is unlikely to
significantly alter the interpretation of the results.
11
2

FET (forced expiratory time)
 Is the time required to perform the FVC
manoeuvre (usually less than 5–6 seconds in
adults and 2–3 seconds in children).
 The FET is increased in the presence of airflow
limitation (often > 12 seconds).
11
3

FEV1, FVC and FER
 Spirometry provides three basic
measurements:
1. The forced vital capacity (FVC)
2. The forced expiratory volume in one
second (FEV1)
3. The ratio of the FEV1/FVC (the forced
expiratory ratio FER, also known as the
FEV1%).
11
5

 All three are needed to interpret spirometry.
 A normal spirogram plots the total volume
exhaled against time.
 The trace becomes flat after about 3–4 seconds
because the total volume of air which can be
exhaled (the FVC) is expelled within this time.
11
6

11
7
Normal spirogram
Approximately 80% of the total volume is exhaled in the first 1
second (the FEV1) and that the curve has reached a plateau by 6
seconds.

 Approximately 80% of this volume (slightly lower
in older people) is exhaled within 1 second, so
the FEV1/FVC ratio is normally 0.7–0.8 or 70–80%.
 Spirometry can demonstrate two basic patterns
of disorder
1. Obstructive
2. Restrictive.
11
8

Obstructive pattern
 In obstructive disorders (for example, asthma or
chronic obstructive pulmonary disease), airflow
is reduced because the airways narrow and
the FEV1 is reduced
 The spirogram may continue to rise for more than
6 seconds because the lungs take longer to
empty.
11
9

Obstructive pattern
 The FVC may also be reduced (because gas is
trapped behind obstructed bronchi) but to a
lesser extent than the FEV1.
 Thus the cardinal feature of an obstructive defect
is a reduction in the FEV1/FVC ratio.
12
0

12
1
Spirogram showing airways
obstruction

 Although the FEV1/FVC ratio is very useful in
diagnosing airflow obstruction, the absolute
value of the FEV1 is the best measure of
severity.
 In general, a reduction in FEV1 to 60–80% of
predicted indicates mild, 40–60% moderate
and less than 40% severe obstruction.
12
2

 Patients with an FEV1 of less than 1 litre are likely
to be limited by dyspnoea.
 If the FEV1 is less than 0.5 litres, the patient is
likely to be breathless at rest and in respiratory
failure.
 Conversely, a patient with an FEV1 of more than
2 litres is unlikely to be short of breath due to
12 airways disease except on vigorous exertion.
3

Obstructive pattern
 Both the FEV1 and the FVC may be reduced, but
the FEV1 is reduced to a greater extent. The
FEV1/FVC ratio is therefore low.
 In this patient, the forced expiratory time is
prolonged and a convincing plateau has not
been reached by 6 seconds.
 Ideally, the patient should continue to blow until
12 a plateau has been reached.
4

Restrictive pattern
 Restrictive disorders can be caused by disease of
the lung parenchyma (such as interstitial lung
fibrosis) or chest wall disease (such as
kyphoscoliosis).
 These prevent full expansion of the lungs and
therefore the vital capacity (VC or FVC) is
reduced.
12
5

 Airflow may be normal or even increased
because the stiffness of fibrotic lungs increases
the expiratory pressure.
 Thus although the absolute value of the FEV1
may be reduced, the FEV1/FVC ratio is normal
or high
12
6
Restrictive pattern

Spirogram showing a Restrictive
disorder
12
7

 Both the FEV1 and FVC may be reduced, but the
FVC is reduced to the same or greater extent
than the FEV1.
 The FEV1/FVC ratio is normal or high.
 The plateau to the curve occurs early.
12
8
Restrictive pattern

 A restrictive pattern on spirometry can be
mimicked by a poor technique.
 Often the FVC is underestimated because the
patient stops blowing too early.
 This will produce a high FEV1/FVC ratio
12
9

Inadequate technique mimicking a
restrictive disorder
13
0

 Inadequate technique mimicking a
restrictive disorder
 The patient stopped blowing too soon.
 The FVC is underestimated and the FEV1/FVC
ratio appears high, giving the impression of a
restrictive disorder.
13
1

 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
13
2

FEF25–75%.
 This is the forced expiratory flow between 25% and
75% of the FVC (also called the maximum mid-expiratory
flow, MMEF).
 This represents the airflow in the medium and small
airways. It is a sensitive but less reliable indicator of
airflow obstruction than the FEV1.
 It may indicate mild airways disease (for example, in
an asthmatic who is currently stable) but has a wide
range of normal values, and should be interpreted
with caution if it is the sole abnormality.
13
3

Quiz Practice 1
A patient’s pulmonary function tests
reveal the following:
 FVC 4.01 L 4.97 L 81
 FEV1 2.58 L 3.67 L 56
 FEV1% 51 >75 _
Select the correct interpretation
a. Restrictive pattern
b. Obstructive pattern
c. Inconclusive
d. Normal

Quiz Practice 2
A patient’s pulmonary function tests reveal the
following:
FVC 3.75 L 4.97 L 75
FEV1 2.80 L 3.67 L 76
FEV1% 75 >/=75 _
Select the correct interpretation
a. Restrictive pattern
b. Obstructive pattern
c. Inconclusive
d. Normal

Quiz Practice 3
Predicted Actual Predicted%
FVC 3.8 4.5 83
FEV1 2.2 4.2 47
FEV1/FVC 82 59 72
FEF25-75 1.6 3.7 43
Survey says … COPD

Quiz Practice 4
Actual Predicted % Predicted
FVC 2.9 4.5 64
FEV1 2.5 4.2 59
FEV1/FVC 89 82 113
FEF25-75 3.7 3.5 102
DLCO is decreased when measured
Restrictive lung pattern from Amiodarone

Quiz Practice 5
FVC 4.0 4.5 88
FEV1 2.6 4.2 57
FEV1/FVC 65 82 71
FEF25-75 1.7 3.6 47
Beta agonist treatment
FVC 4.1 4.5 91
FEV1 3.6 4.2 89
FEV1/FVC 90 82 112
FEF25-75 3.2 3.6 91
Reversible obstructive defect

Quiz Practice 6
FVC 4.0 4.5 88
FEV1 3.6 4.2 89
FEV1/FVC 90 82 112
FEF25-75 3.1 3.4 95
Normal 

Quiz Practice 7
FVC 4.0 4.5 88
FEV1 3.3 4.2 81
FEV1/FVC 83 82 101
FEF25-75 1.7 3.5 48
Small Airways Defect

Quiz Practice 8
FVC 3.5 5.3 68
FEV1 3.1 4.6 68
FEV1/FVC 93 82 117
FEF25-75 3.7 3.3 120
By the way, the patient’s BMI = 47
…
Restrictive pattern in obese patient

Quiz Practice 9
Predicted
Values
Measured
Values
% Predicted
FVC 6.00 liters 4.00 liters 67 %
FEV1 5.00 liters 2.00 liters 40 %
FEV1/FVC 38 % 50 % 60 %
Decision : This person is obstructed

Quiz Practice 10
Predicted
Values
Measured
Values
% Predicted
FVC 5.68 liters 4.43 liters 78 %
FEV1 4.90 liters 3.52 liters 72 %
FEV1/FVC 84 % 79 % 94 %
Decision : This person is restricted

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