Spirometry Interpretation

Data generated
 Volume time curve (spirogram)
 FEV1, FVC, Ratio
 Flow volume loop
 Peak flow
 FVC
 FEF 25-75%
MEF 75, 50, and 25
 Inspiratory flow data

Normal Values
 FVC
 80 – 120% of predicted is a normal
value
 70 – 80% demonstrates mild
reduction/restriction
 50 – 70% demonstrates moderate
reduction
<50% demonstrates severe
reduction

Normal Values
 FEV1
 80 – 120% of predicted is a
normal value
 70 – 80% demonstrates mild
reduction/restriction
 50 – 70% demonstrates moderate
reduction
<50% demonstrates severe
reduction

Normal Values
 FEF25-75 reflects small airway function
● >80% is normal
● 60 – 80% reflects mild obstruction
in the small airways
● 40 – 60% reflects moderate
obstruction
● <40% reflects severe obstruction

Criteria for Normal
Post-bronchodilator Spirometry
 FEV1: % predicted > 80%
 FVC: % predicted > 80%
 FEV1/FVC: > 0.7 - 0.8, depending on
age

Obstructive Pattern
o Decreased FEV1/FVC
- <70% predicted
o Decreased FEV1 < 80% predicted
o FVC can be normal or reduced –
usually to a lesser degree than FEV1
o FEV1 used to grade the severity

Restrictive Pattern
 FEV1: Normal or mildly reduced
 FVC: < 80% predicted
 FEV1/FVC: Normal or increased > 0.7

Mixed Obstructive/Restrictive
 FEV1: < 80% predicted
 FVC: < 80% predicted
 FEV1 /FVC: < 0.7

Notes
➔ Spirometry which is not performed
correctly may produce misleading results.
➔ The FEV1, FVC and FEV1/FVC ratio are all
necessary to interpret spirometry.
➔ An obstructive defect causes a reduction
in FEV1 and a reduced FEV1/FVC ratio.
➔ Restrictive defects cause a reduction in
FVC with a normal or high FEV1/FVC ratio.

Notes
➔ 12% and 200 mL or more improvement
in either FEV1 or FVC after bronchodilator
indicates significant reversibility.
➔ The FEV1/FVC ratio should not be used to
assess reversibility.
➔ Correct interpretation of spirometry
requires that it be performed correctly
(ATS/ERS criteria for acceptable and
repeatable Spirometry).

To obtain an accurate recording the subject
should be told to:
• Sit up straight
• Get a good seal around the mouthpiece of the
spirometer
• Rapidly inhale maximally (‘breathe in all the
way’)
• Without delay, blow out as hard and as fast
as possible (‘blast out’)
• Continue to exhale (‘keep going … keep
going’) until the patient can blow no more.

Expiration should continue for at least 6
seconds (3 seconds in children under 10
years old) and up to 15 seconds if necessary
(some patients will find this exhausting and
prolonged manoeuvres should be used with
caution)
Manoeuvres are repeated until at least three
technically acceptable manoeuvres (NO
coughs, air leaks, false starts) are completed.

If required, more tests should be done to try
to meet repeatability criteria (no more than
8 attempts in total).
Poor measurement technique can produce
results which mimic disease patterns.
Common errors occur when the patient fails
to inhale fully before the test, stops blowing
too early (apparent restrictive defect), or
doesn’t blow out hard enough (apparent
obstructive defect).

TECHNIQUE OF SPIROMETRY
The patient must be clinically stable, should sit
straight, with head erect, nose clip in place, and
holding the mouthpiece tightly between the lips.
Initially, he or she should breathe in and out at
the tidal volume ( V T : normal quiet breathing)
to record the tidal flow–volume loop.
Then, when the patient is ready, the technician
instructs him/her to inhale maximally to TLC ,
and then exhale as fast and as completely as
possible to record the FVC .

TECHNIQUE OF SPIROMETRY
The point at which no more air can be
exhaled is the RV .
The patient is then instructed to inhale fully
to TLC again in order to record the IVC .
This test is then repeated to ensure
reproducibility in order to meet quality
control criteria (American Thoracic Society
or ATS criteria) .

Flow/Volume loop
12
8
4
0
-4
-8
Flow (L/s)
PEF
Man
176 cm
76 kg
Volume (L)

ATS/ERS criteria for acceptable and
repeatable Spirometry
ACCEPTABILITY CRITERIA
1.Free from artefacts (such as cough or
glottis closure early in expiration)
2.Free from leaks
3.Good starts
— extrapolation back from the peak flow
(which is the steepest part of the spirogram
curve) produces a theoretical start time from
which the measurements should be timed.
This ‘new time zero’ should occur within 5%
of the FVC or within 150 mL

Acceptability Criteria
Acceptable exhalation
— Adults: at least 6 seconds of exhalation
and a plateau in the volume
curve (plateau = no detectable change in
volume over 1 second)
— Children aged under 10: at least 3
seconds of exhalation and a plateau in
the volume curve

Acceptability
The ATS mandates three acceptable maneuvers.
The number of trials that can be performed on an
individual should not exceed 8.
An acceptable trial should have
a good start, a good end, and absence of artifacts.
1. Good start of the test:
• If the study needs back extrapolation, the
extrapolation volume should not exceed 5% of
FVC or 150 ml, whichever is larger.

Note : Back extrapolation applies to the VT curve and
means that if the start of the test is not optimal,
correction can be made by shifting the time axis forward,
provided that the extrapolation volume is within either
one of the limits mentioned earlier.
To simplify this, consider that a patient’s FVC is 2 L and
the study requires a back extrapolation correction, and
5% of the FVC (2 L) is 100 ml. Because 150 ml is larger
than 5% of the patient’s FVC (100 ml), 150 ml should be
used as the upper limit of extrapolated volume.
Then, if the measured extrapolated volume is greater
than 150 ml, the result cannot be accepted.

Extrapolation volume of 150 ml or 5% of
FVC (whichever is larger)

Note : A good start of the study can be
identified qualitatively on the FV curve as a
rapid rise of flow to PEF from the baseline (0
point), with the PEF being sharp and
rounded.
The FEV 1 can be over- or underestimated
with submaximal effort, which may mimic
lung disorders such as those due to airway
obstruction or lung restriction;

2. Smooth flow–volume (FV) curve, free of artifacts :
These artifacts will show in both volume–time (VT) and
FV curves but will be more pronounced in the FV curve.
These artifacts include the following:
(a) Cough during the 1st second of exhalation may
significantly affect FEV 1 .
The FV curve is sensitive in detecting this artifact;
Coughing after the 1st second is less likely to make
a significant difference in the FVC and so it is accepted
provided that it does not distort the shape of the FV
curve (judged by the technician).

(a) Cough during the 1st second of
exhalation may significantly affect FEV 1 .
Cough in the 1st second. It is much clearer in the FV
curve than in the VT curve as indicated by the arrows

(c) Glottis closure;
(d) Early termination of effort.
(e) Obstructed mouthpiece, by applying the
tongue through the mouthpiece or biting it
with the teeth.
(f) Air leak :
• The air leak source could be due to loose tube
connections or, more commonly, because the
patient weakly applies lips around the
mouthpiece. Air leak can be detected from the
FV loop

3. Good end of the test (demonstrated in the
VT curve):
(a) Plateau of VT curve of at least 1 s,
i.e.volume is not changing much with time
indicating that the patient is approaching the
residual volume (RV).
OR
(b) Reasonable duration of effort (FET) :
• Six seconds is the minimum accepted duration
(3 s for children) .
• Ten seconds is the optimal.
.

• FET of >15 s is unlikely to change the
clinical decision and may result in the
patient’s exhaustion.
Patients with obstructive disorders can
exhale for more than 40 s before reaching
their RV, i.e., before reaching a plateau in the
VT Curve
Normal individuals, however, can empty
their lung (i.e., reach a plateau) within 4 s

(c) The patient cannot or should not continue
to exhale.
Note : A good end of the study can be shown in
the FV curve as an upward concavity at the
end of the curve.
A downward concavity, however, indicates
that the patient either stopped exhaling
(prematurely) or started inhaling before
reaching the RV .
This poor technique may result in
underestimation of the FVC.

Poor end in comparison to good end (small upward concavity)
of FV curve. A poor end (downward concavity) indicates premature
termination of exhalation (before 0 flow)

REPEATABILITY CRITERIA
• Three acceptable manoeuvres (meeting above criteria)
• The two largest FVC measurements within 150mL of
each other
• The two largest FEV1 measurements within 150mL of
each other
When both acceptability and repeatability criteria are
met, the test can be concluded.
Up to 8 manoeuvres should be performed until the
criteria are met or the patient is unable to continue.
As a minimum, the three satisfactory (or best)
manoeuvres should be saved.

Reproducibility
After obtaining three acceptable maneuvers, the
following reproducibility criteria should be
applied:
– The two largest values of FVC must be within
150 ml of each other.
– The two largest values of FEV 1 must be within
150 ml of each other.
If the studies are not reproducible, then the
studies should be repeated until the ATS criteria
are met or a total of eight trials are completed or
the patient either cannot or should not continue
testing.

• The final values should be chosen based on the following :
– FEV1 and FVC should be reported as the highest values from
any acceptable/reproducible trial (not necessarily from the
same trial).
– The other flow parameters should be taken from the best
test curve (which is the curve with the highest sum of FVC +
FEV1).
– If reproducibility cannot be achieved after eight trials,
the best test curve (the highest acceptable trial) should be
reported. The technician should comment on this deviation
from protocol so that the interpreting physician understands
that the results may not be accurate.
.

Acceptable and reproducible trials

Acceptable trials are not necessarily
reproducible,because the patient may not produce
maximum effort in all trials

Keep in mind that the lack of any of these features
may indicate a lung disorder rather than a poor study

Spirometry interpretation
 Obstructive v. Restrictive
 Mid flow obstruction
 Shape of the FV loop
Obstruction v. restriction
 Fixed large airway obstruction
 Variable airway obstruction
1. Extrathoracic
2. Intrathoracic

Key Notes
1. be conservative in suggesting a
specific diagnosis based only on
pulmonary function abnormalities.
2. Interpret borderline normal values
with caution.
3. First step = to evaluate and comment
on the quality of the tests.

Good Measurements are Essential!
Acceptable
Loop
Unacceptable
Loop

Quality Check
Patient should
exhale suddenly
and forced.
Patient should exhale
suddenly and forced
Patient should cough
before starting the
measurement
Patient should inhale
longer and to the
maximum
Patient should exhale
as long as possible;
minimal 6 s
www.spiro-webCard.de

 The standard normal values roughly range
from 80 to 120% of the predicted values
that are derived from Caucasian studies.
 When you interpret a PFT, you should
always look at the patient’s results as
percentage of the predicted values for that
particular patient (written in the report as
% pred.).
 If the patient is normal, then his/her
values should roughly lie within 80–120%
of predicted values.*

59
Obstructive
Lung dis.
RLD
Interinsic
RLD
Extrinsic
FEV1
FVC
FEV1/FVC
RV
TLC
RV/TLC
VC
FRC

● Only need to look at 5 numbers
● Look at the post bronchodilator values too!
FEV1
% Predicted
FVC % Predicted
FER
(FEV1 / FVC ratio)

Features of obstructive disorders
 Diagnostic features: ↓ FEV 1 /FVC
ratio
 Other features:
 ↓ FEV 1
 ↓ FVC (can be normal)
 ↓ FEFs and MMEF (FEF 25 , FEF 50, FEF
75 , FEF 25–75 )
 ↓ PEF
 ↓ FET
 Significant bronchodilator response
 Scooped (concave) descending limb of FV
curve

Obstructive Disorders
 The two major obstructive disorders are
bronchial asthma and COPD .
 The key to the diagnosis of these
disorders is the drop in FEV 1 /FVC ratio.

 FEV 1 may be reduced too and is used to
define the severity of obstruction
 FVC may be reduced in obstructive
disorders but usually not to the same
degree as FEV 1 .

 The flow–volume curve can be used alone to
confidently make the diagnosis of obstructive
disorders, as it has a distinct shape in such
disordersThese features include the following:
– The height of the curve (PEF) is much less than
predicted.
– The descending limb is concave (scooped), with
the outward concavity being more pronounced
with more severe obstruction.
– The slope of the descending limb that represents
MMEF and FEFs is reduced due to airflow
limitation at low lung volumes.

There are five features that make the diagnosis
of a significant airway obstruction definite,
based on The FV curve alone.
1 – Decreased PEF when compared to the
predicted curve.
2 – Scooping of the curve after PEF, indicating
airflow limitation.
3 – The 1st second mark is almost in the middle
of the curve indicating that the FEV 1 and
FEV 1 /FVC ratio are significantly
decreased.

4 – FVC is decreased when compared to the
predicted curve.
5 – The inspiratory component of the curve is normal,
excluding a central airway obstruction.
( b ) There is a clear response to bronchodilators
indicating reversibility and supporting the
diagnosis of an obstructive disorder, most likely
bronchial asthma

 Lack of bronchodilator response does not
exclude bronchial asthma as
responsiveness can vary over time.
 Similarly many patients with COPD can
show reversibility.
 Reversibility in the correct clinical
context (i.e. young nonsmoker) supports
the diagnosis of asthma.

• 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

Mild airway obstruction, with prolonged duration of exhalation (20 s)

• Special Conditions
– In emphysema and because of loss of
supportive tissues, the airways tend to
collapse significantly at low lung volumes,
giving a characteristic “dog-leg” appearance
in FV curve

Features of restrictive disorders
 Most important features: ↓ FVC
and normal or ↑ FEV 1 /FVC ratio
 Other features:
 ↓ FEV 1 (proportional to FVC), but it
can be normal
 ↓ MMEF
 PEF: normal, increased, or decreased
 Steep descending limb of FV curve

Restrictive Disorders
 In restrictive disorders, such as pulmonary
fibrosis, the key to the diagnosis is the drop in
FVC, as the volume of the air spaces is
significantly lower than normal.

 The lung elasticity increases and the lungs
retract.
 The FEV 1 /FVC ratio has to be preserved or
increased.

 To make a confident diagnosis of a restrictive
disorder, the TLC should be measured and
should be low.
 So, based on spirometry alone, the earlier
features are reported as suggestive (not
diagnostic) of a restrictive disorder.
 Remember that normal FVC or VC excludes
lung restriction.

FV curve features of different forms of restriction:
( a ) ILD with witch’s hat appearance;
( b ) chest wall restriction (excluding NMD);

FV curve features of different forms of restriction:
( c ) NMD (or poor effort study) producing a
convex curve

This is a widely used grading system but different
organizations use different systems of grading.

GRADING OF SEVERITY
 Different variables and values were used to
grade severity of different pulmonary disorders
 Recently, FEV 1 has been selected to grade
severity of any spirometric abnormality
(obstructive, restrictive, or mixed)
 The traditional way of grading severity of
obstructive and restrictive disorders involve the
following:

GRADING OF SEVERITY
 The traditional way of grading severity
of obstructive and restrictive disorders
involve the following:
– In obstructive disorders, the FEV1/FVC
ratio should be <0.7, and
– The value of FEV1 is used to determine
severity

GRADING OF SEVERITY
– In restrictive disorders, however, FEV1/FVC
ratio is normal and the TLC is less than
80% predicted.
– The ATS suggested using the TLC to grade
the severity of restrictive disorders, which
cannot be measured in simple spirometry.
– Where only spirometry is available, FVC
may be used to make that grading.
– The TLC, however, should be known before
confidently diagnosing a restrictive
disorder

Nomogram
algorithm for
separating
obstructive from
restrictive defects
Nomogram
algorithm for
separating
obstructive from
restrictive defects

Spirometry interpretation
Inhaled B2
reverse
11/13/14
FEV1/FVC
Obstruction
Mixed*
*
FVCต้อง
ตำ่ำ
FVC
Normal
Mixed Restriction* FEF25-75%
Small
airway
disease
Normal
spirometry
Reversible
airway
obstruction
Irreversible
airway
obstruction
Low
Low
Low Normal
Yes No
Normal or Increase
* Definite Dx ดู
TLC

Diagnostic Flow Diagram for Restriction
Is FEV1 / FVC Ratio Low? (<70%)
Is FVC Low?(<80% pred)
Yes No
Restrictive Defect Normal Spirometry
Further Testing with
Full PFT’s; consider
referral if moderate to
severe
No
Adapted from Lowry, 1998

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.

90 American family physican 2004

 Know the 3 aspects of lung function
test:
1) spirometry
2) volumes
3) diffusion

Normal values
Spirometry:
 FEV1 and FVC >80% predicted.
 FEV1/FVC >80% predicted.
Volumes: 80-120%.
Diffusion: 75-125%.

 Low FVC suggest possible restriction
but need to look at TLC to confirm
(TLC <80%)
 High FRC and TLC (>120%
predicted) suggest hyperinflation.
 High RV/TLC suggest gas trapping.

Case (1)
 FEV1/FVC: 48%
 FVC: 3.24L (86%)
 FEV1: 1.55L (48%)
 FEF25-75%: 0.64L (28%)

Case (1)
 FEV1/FVC: 48% Severely ↓
 FVC: 3.24L (86%) Normal
 FEV1: 1.55L (48%) Severely ↓
 FEF25-75%: 0.64L (28%)
Severely ↓
 Interpretation:
Moderate obstruction

Case (2)
 FEV1/FVC: 59%
 FVC: 2.27L (71%)
 FEV1: 1.34L (49%)
 FEF25-75%: 0.95L (22%)

Case (2)
 FEV1/FVC: 59% Moderately ↓
 FVC: 2.27L (71%) Mildly ↓
 FEV1: 1.34L (49%) Severely ↓
 FEF25-75%: 0.95L (22%)
Severely ↓
 Interpretation: Moderate obstructive
impairment, FVC mildly reduced, can
not rule out restrictive impairment

Case (3)
 FEV1/FVC: 86%
 FVC: 2.49 L (61%)
 FEV1: 1.96 L (64%)
 FEF25-75%: 2.83 L (98%)
 FRC: 1.94 L (59%)
 TLC: 4.03 L (70%)
 RV: 1.38 L (65%)
 DLCO: 55%
Interpretation: Moderate Restrictive pattern
with moderately reduced DLCO

Case (4)
 FEV1/FVC: 56%
 FVC: 2.54 (68%)
 FEV1: 1.41 (49%)
 DLCO: 68%

Case (4)
 FEV1/FVC: 56% Moderately ↓
 FVC: 2.54 (68%) Mildly ↓
 FEV1: 1.41 (49%) Severely ↓
 DLCO: 68% Mildly ↓
 Interpretation: Severe obstruction,
maybe restrictive, reduced DLCO

Male 57 years, 182 cm, 78 kg
Pred. best % (B/P)
FVC 4.86 4.92 101
FEV1 3.68 3.74 102
FEV1/FVC% 77 76 99
FEF25/75 3.44 3.10 88
Normal

Pred. best % (B/P)
FVC 3.71 3.51 95.1
FEV1 3.12 2.35 75.3
FEV1/FVC% 83,8 62.2 74.4
FEF25/75 4.31 1.8 41
Mild obstruction with small airway affection

Pred. best % (B/P)
FVC 4.60 3.25 78
FEV1 3.55 0.76 22
FEV1/FVC% 77 22 29
FEF25/75 3.51 0.22 6.1
Severe obstruction with small airway
affection

Pred. best % (B/P)
FVC 4.10 1.45 33
FEV1 3.25 3.10 96
FEV1/FVC% 83
Severe restriction

A 71 yrs male
Height :175 ,weight :88
FVC:45%
FEV1: 31%
FEV1/ FVC :53%
FEF25-75 :15%
TLC :142%
Very Severe obstruction

Meas Ref Pred%
FVC 2.2 2.58 85
FEV1 1.79 1.85 97
FEV1/FVC 81 72
FEF 25-75 1.82 2.23 82
PEF 5.67 5.2 109
Normal

A 75 year old female has a history of
dyspnea and palpitations
Meas Ref Pred%
FVC 2.62 2.82 93
FEV1 1.45 1.98 72
FEV1/FVC 55 69
FEF25-75 0.43 2.20 20
PEF 4.50 5.48 82
Interpretation: mild obstruction

Interpretation: moderate obstruction

Actual Predicted % Predicted
FVC 4.0 4.5 88
FEV1 3.4 4.2 89
FEV1/FVC 85 82 112
FEF25-75
Normal

FVC 2.0 4.0 50
FEV1 1.8 3.7 47
FEV1/FVC 90 82 112
FEF25-75
Restrictive Pattern

FVC 4.0 4.5 88
FEV1 2.4 4.2 58
FEV1/FVC 60 82 76
FEF25-7 2.2 4.4 50
Obstructive Pattern

A 36 yrs female
FVC:89%
FEV1: 94%
FEV1/ FVC :89%
FEF25-75 :131%
TLC :92%
Normal

A 30 yrs male
Height :186,weight :68
FVC:19%
FEV1: 21%
FEV1/ FVC :93%
FEF25-75% :48%
TLC :28%
Very Severe restriction

A 26 yrs male
FVC: 97%
FEV1: 77%
FEV1/ FVC :66%
FEF25-75 :48%
Mild obstruction

A 30 yrs male
FVC: 88%
FEV1: 69%
FEV1/ FVC :66%
FEF25-75 :38%
VEXT : 90
Moderate obstruction

Case Study 1
 A 53-year-old white male presents for
annual visit.
 Although he quit 10 years ago he is a
previous cigarette smoker with a 20
pack-year history.
 During the past 12 months, he has had
3 episodes of bronchitis.
 His history of tobacco use and recent
episodes of acute bronchitis lead you
to perform spirometry.

Results
Pre-
Bronchodilator
Post-
Bronchodilator
Predicted Measured % Measured % %
change
FVC 4.65 4.65 100 4.95 106 6
FEV1 3.75 3.13 83 3.34 89 6
FEV1/FV
80 67 -13 67 -13 0
C
PEF 511 462 90 522 102 12
FEF 25 7.86 5.7 73 6.00 76 5
FEF 50 4.46 2.3 52 2.10 47 -9
FEF 75 1.75 .5 29 0.60 35 18
FEF 25-75 3.76 1.77 47 1.78 47 0

Results
Pre-
Bronchodilator
Post-
Bronchodilator
Predicted Measured % Measured % %
change
FVC 4.65 4.65 100 4.95 106 6
FEV1 3.75 3.13 83 3.34 89 6
FEV1/FVC 80 67 -13 67 -13 0
Is there obstruction?
FEV1/FVC = 67 % of predicted; therefore,
obstruction present
Is there restriction?
FVC = 100 % of predicted; therefore, no restriction
present

Results
Pre-Bronchodilator Post-Bronchodilator
Predicte
d
Measured % Measured % % change
FVC 4.65 4.65 100 4.95 106 6
FEV1 3.75 3.13 83 3.34 89 6
FEV1/FVC 80 67 -13 67 -13 0
What is the severity of obstruction?
FEV1 is 83% of predicted; therefore, the obstruction is mild
Is the obstruction reversible (is reversibility present)?
FEV1 increases from 83% to 89% (6% increase) and increases
from 3,130 cc to 3,340 cc (increase of 210 cc)
Interpretation: Mild Obstruction with minimal reversibility: Mild
COPD

Case Study 2
A 33 year old female presents to the office
complaining of dyspnea and cough for the
past 2 days. Her cough is productive of a
white mucous.
Her past medical history is significant for
asthma since childhood, obesity,
gastroesophageal reflux disease (GERD),
and an occasional migraine headache. She
is a nonsmoker and has no known
allergies.

Case Study 2 (cont)
Her current medications include the
following:
1. Albuterol 2 puffs po qid prn
wheezing, cough, or dyspnea
2. Fluticasone 110 micrograms 2 puffs
po bid
3. Ranitidine 150 mg po bid
Her father recently died secondary to
advanced COPD.
Due to her symptoms, you order
spirometry.

Results
Predicte
d
FVC 3.78 1.92 51 2.7 71 34
FEV1 3.24 1.11 34 1.61 50 36
FEV1/ FVC 86 58 -28 60 -26 3
Obstruction?
FEV1/FVC = 60%; therefore, obstruction present
Restriction?
FVC = 51% of predicted; therefore, restriction
present

Results
Predicte
d
FVC 3.78 1.92 51 2.7 71 34
FEV1 3.24 1.11 34 1.61 50 36
FEV1/ FVC 86 58 -28 60 -26 3
•Is the obstruction reversible (is reversibility present)?
FEV1 increases from 34% to 50% (16% increase) and increases
by 500 cc
•What is the severity of restriction?
Restriction improves as the FVC changes from 51% to 71% with
bronchodilator, indicating that the “air trapping” is relieved. (As
an aside, if restriction is only mild, obesity may be the cause)
Interpretation: obstruction with reversibility (Moderate
obstruction)

Spirometry Interpretation

In this document