Pulmonary function testing

Pulmonary Function Testing
The Basics of Interpretation

Anatomy
• Lungs comprised of
– Airways
– Alveoli

http://www.aduk.org.uk/gfx/lungs.jpg

The Airways
• Conducting zone: no
gas exchange occurs
– Anatomic dead
space
• Transitional zone:
alveoli appear, but are
not great in number
• Respiratory zone:
contain the alveolar
sacs
Weibel ER: Morphometry of the Human
Lung. Berlin and New York: SpringerVerlag, 1963

The Alveoli
• Approximately 300
million alveoli
• 1/3 mm diameter
• Total surface area if
they were complete
spheres 85 sq.
meters (size of a
tennis court)
Murray & Nadel: Textbook of Respiratory
Medicine, 3rd ed., Copyright © 2000 W. B.
Saunders Company

Pulmonary function test :
Group of procedures that measure the function of the
lungs

1.
2.
3.
4.

Spirometry
Lung volumes
Gas transfer
Bronchial chalenge

Spirometry
• Measurement of the pattern of air
movement into and out of the lungs during
controlled ventilatory maneuvers.
• Often done as a maximal expiratory
maneuver

Spirometry
Measures flow, volumes
 Volume vs. Time
 Can determine:
- Forced expiratory volume in one second (FEV1)
- Forced vital capacity (FVC)
- FEV1/FVC
- Forced expiratory flow 25%-75% (FEF25-75)

What is a spirometry ??
Spirometry is a measure of airflow and
lung volumes during a forced expiratory
maneuver from full inspiration

1. Volume Time Graph

2. Flow-volume loops

Terminology
• Forced vital capacity
(FVC):
– Total volume of air that can
be exhaled forcefully from
TLC
– The majority of FVC can be
exhaled in <3 seconds in
normal people, but often is
much more prolonged in
obstructive diseases
– Measured in liters (L)

FVC
• Interpretation of % predicted:
–
–
–
–

80-120%
70-79%
50%-69%
<50%

Normal
Mild reduction
Moderate reduction
Severe reduction

FVC

Terminology
• Forced expiratory volume
in 1 second: (FEV1)
– Volume of air forcefully
expired from full inflation
(TLC) in the first second
– Measured in liters (L)
– Normal people can exhale
more than 75-80% of their
FVC in the first second;
thus the FEV1/FVC can be
utilized to characterize
lung disease

FEV1
• Interpretation of % predicted:
–
–
–
–

>75%
60%-75%
50-59%
<49%

Normal
Mild obstruction
Moderate obstruction
Severe obstruction

FEV1

FVC

Terminology
• Forced expiratory flow 2575% (FEF25-75)
– Mean forced expiratory flow
during middle half of FVC
– Measured in L/sec
– May reflect effort
independent expiration and
the status of the small
airways
– Highly variable
– Depends heavily on FVC

Volume Time Graph
The volume is plotted against the time, it displays
the expiration.

1. FVC
2. FEV1
3. FEV1/FVC
4. FEF25%
5. FEF75%

Forced Vital Capacity (FVC)
The total amount of air expired as
quickly as possible after taking the
deepest possible breath.

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

FEV1/FVC
Ratio of FEV1 to FVC :
It indicates what percentage of the total FVC
was expelled from the lungs during the first
second of forced exhalation
This value is critically important in the
diagnosis of obstructive and restrictive
diseases

FEF25%
Amount of air that was forcibly expelled in the first
25% of the total forced vital capacity test.

FEF75%
The amount of air expelled from the lungs during the
first (75%) of the forced vital capacity test.

FEF25%-75%
The amount of air expelled from the lungs during the
middle half of the forced vital capacity test.

Obstructive Pattern
■ Decreased FEV1
■ Decreased FVC
■ Decreased FEV1/FVC
- <70% predicted
■ FEV1 used to follow severity in COPD

Obstructive Lung Disease —
Differential Diagnosis
 Asthma
 COPD
- chronic bronchitis
- emphysema
 Bronchiectasis
 Bronchiolitis
 Upper airway obstruction

Restrictive Pattern

 Decreased FEV1

 Decreased FVC
 FEV1/FVC normal or increased

Restrictive Lung Disease —
Differential Diagnosis
 Pleural
 Parenchymal
 Chest wall
 Neuromuscular

Bronchodilator Response
 Degree to which FEV1 improves with inhaled
bronchodilator
 Documents reversible airflow obstruction
 Significant response if:

- FEV1 increases by 12% and >200ml
 Request if obstructive pattern on spirometry

Flow Volume Loop
 “Spirogram”
 Measures forced inspiratory and
expiratory flow rate
 Augments spirometry results
 Indications: evaluation of upper airway
obstruction (stridor, unexplained dyspnea)

Flow-Volume Loop
• Illustrates maximum
expiratory and
inspiratory flowvolume curves
• Useful to help
characterize disease
states (e.g.
obstructive vs.
restrictive)
Ruppel GL. Manual of Pulmonary Function Testing, 8th ed.,
Mosby 2003

Obstructive Disorders
• Characterized by a
limitation of expiratory
airflow
– Examples: asthma,
COPD

• Decreased: FEV1,
FEF25-75, FEV1/FVC
ratio (<0.8)
• Increased or Normal:
TLC

Restrictive Lung Disease
• Characterized by diminished lung
volume due to:
– change in alteration in lung
parenchyma (interstitial lung
disease)
– disease of pleura, chest wall
(e.g. scoliosis), or
neuromuscular apparatus (e.g.
muscular dystrophy)
• Decreased TLC, FVC
• Normal or increased: FEV1/FVC
ratio

Upper Airway Obstruction
 Variable intrathoracic obstruction
 Variable extrathoracic obstruction
 Fixed obstruction

Fixed obstruction
1. Post intubation stenosis
2. Goiter
3. Endotracheal neoplasms
4. Bronchial stenosis
Maximum airflow is limited
to a similar extent in both
inspiration and expiration

Variable extrathoracic
Obstruction
1. Bilateral and unilateral vocal cord
paralysis
2. Vocal cord constriction
3. Reduced pharyngeal crosssectional area
4. Airway burns

The obstruction worsens in
inspiration because the
negative pressure narrows
the trachea and inspiratory
flow is reduced to a greater
extent than expiratory flow

In variable intrathoracic
obstruction
1. Tracheomalacia
2. Polychondritis
3. Tumors of the lower trachea or
main bronchus.
The narrowing is maximal in
expiration because of
increased intrathoracic
pressure compressing the
airway.
The flow volume loop shows a
greater reduction in the
expiratory phase

Lung Volumes
 Measurement:
- helium
- nitrogen washout
- body plethsmography
 Indications:
- Diagnose restrictive component
- Differentiate chronic bronchitis from
emphysema

Lung Volumes – Patterns
 Obstructive
- TLC > 120% predicted
- RV > 120% predicted
 Restrictive
- TLC < 80% predicted
- RV < 80% predicted

Diffusing Capacity
 Diffusing capacity of lungs for CO
 Measures ability of lungs to transport inhaled gas
from alveoli to pulmonary capillaries
 Depends on:
- alveolar—capillary membrane
- hemoglobin concentration
- cardiac output

Diffusing Capacity
 Decreased DLCO
(<80%
predicted)

 Increased DLCO
(>120-140% predicted)

 Asthma (or normal)

 Obstructive lung disease
 Pulmonary hemorrhage
 Parenchymal disease
 Polycythemia
 Pulmonary vascular
disease
 Anemia

 Left to right shunt

DLCO — Indications

 Differentiate asthma from emphysema
 Evaluation and severity of restrictive lung
disease
 Early stages of pulmonary hypertension

Case 1
CC/HPI: A 36yo WM, nonsmoker, presents to your
clinic with c/o episodic cough for 6mo. Also
reports occasional wheezing and dyspnea with
exertion during softball practice.
Exam: Heart RRR, no murmurs; Lungs CTAB, no
labored breathing
Based on your exam and a thorough review of
systems, you suspect asthma and decide to
order spirometry for further evaluation.

Continued…
PFTs: FEV1
FEV1/FVC

86% predicted
82% predicted

Flow Volume Loop: normal inspiratory and
expiratory pattern
You still suspect asthma. What is your next
step in the workup of this patient?

Bronchoprovocation
 Useful for diagnosis of asthma in the
setting of normal pulmonary function tests
 Common agents:
- Methacholine, Histamine, others
 Diagnostic if: ≥20% decrease in FEV1

Continued…
SYMPTOMS

↓
PFTs

↓
OBSTRUCTION?

↓

↓

YES

NO

↓

↓

TREAT

BRONCHOPROVOCATION

↓

↓

Obstruction?

No Obstruction?

TREAT

Other Diagnosis

Obstructive Pattern — Evaluation
 Spirometry
 FEV1, FVC:

decreased

 FEV1/FVC:

decreased

 FV Loop

“scooped”

 Lung Volumes
 TLC, RV:

increased

 Bronchodilator responsiveness

(<70% predicted)

Restrictive Pattern – Evaluation
 Spirometry
 FVC, FEV1:

decreased

 FEV1/FVC:

normal or increased

 FV Loop

“witch’s hat”

 DLCO

decreased

 Lung Volumes
 TLC, RV:

decreased

PFT Patterns
 Emphysema

 Chronic Bronchitis

 FEV1/FVC <70%

 FEV1/FVC <70%

 “Scooped” FV curve

 “Scooped” FV curve

 TLC increased

 TLC normal

 Increased compliance

 Normal compliance

 DLCO decreased

 DLCO usually normal

PFT Patterns
 Asthma
 FEV1/FVC

normal or decreased

 DLCO

normal or increased

But PFTs may be normal  bronchoprovocation


Which of the following is used to follow disease severity in
COPD patients?
a.
b.
c.
d.
e.

Total lung capacity (TLC)
Degree of responsiveness to bronchodilators
Forced vital capacity (FVC)
Forced expiratory volume in 1 second
Diffusing capacity (DLCO)


A 36yo WF, non-smoker, presents to your office for follow-up
of ‘recurrent bronchitis.’ You suspect asthma and decide
to order spirometry. Which of the following would you
include in your prescription for testing?
a.
b.
c.
d.
e.

Diffusing Capacity (DLCO)
If no obstruction present, add trial of bronchodilator
If no obstruction present, perform methacholine challenge
Flow volume loop
b and c


A 68yo HM is admitted to the ICU with acute respiratory
distress. A CXR obtained in the ED demonstrates
bilateral pulmonary infiltrates, and his DLCO is
elevated. What is the most likely diagnosis?
a.
b.
c.
d.
e.

Pulmonary edema
Aspiration pneumonitis
Pulmonary emboli
Alveolar hemorrhage
Interstitial lung disease












Hemoptysis of unknown origin
Pneumothorax
Unstable angina pectoris
Recent myocardial infarction
Thoracic aneurysms
Abdominal aneurysms
Cerebral aneurysms
Recent eye surgery (increased intraocular pressure
during forced expiration)
Recent abdominal or thoracic surgical procedures
History of syncope associated with forced exhalation

Obstructive V/S restrictive lung
disease ???

Common Obstructive Lung Diseases
• Asthma
• COPD (chronic bronchitis, emphysema and
the overlap between them).

• Cystic fibrosis.

-Airflow is reduced because the airways narrow and the FEV1 is
reduced
-Spirogram may continue to rise for more than 6 seconds because lung
take longer to empty
-FVC may also be reduced because gas is trapped behind obstructed
bronchi due to increase in intrathoracic pressure during maneuver
compresses airways causing early airway closure and gas trapping but
this reduction to a lesser extent than FEV1

FEV1 ≥ 80%
of predicted Normal
FEV1 60-80%
of predicted mild obst.
FEV1 40-60%
of predicted moderate
FEV1 ≤ 40%
of predicted severe
The cardinal feature is FEV1/FVC ratio If
the ratio less than 70 consider obstructed
disease .
*Predictors: Sex, Age, Ht

Flow volume loop in
Obstructive lung disease

Asthma
 Peak expiratory flow reduced
so maximum height of the loop
is reduced
 Airflow reduces rapidly with the
reduction in the lung volumes
because the airways narrow
and the loop become concave
 Concavity may be the indicator
of airflow obstruction and may
present before the change in
FEV1 or FEV1/FVC

Emphysema
Airways may collapse during
forced expiration because of
destruction of the supporting
lung tissue causing very
reduced flow at low lung
volume and a characteristic
(dog-leg) appearance to the
flow volume curve

Reversibility
• Improvement in FEV1 by 12-15%
or 200 ml in repeating
spirometry after treatment with
Sulbutamol 2.5mg or ipratrobium
promide by nebuliser after 15-30
minutes
• Reversibility is a characterestic
feature of B.Asthma
• In chronic asthma there may be
only partial reversibility of the
airflow obstruction
• While in COPD the airflow is
irriversible although some cases
showed significant improvement.

Interpretation of PFTs
Step 1. Look at the Flow-Volume loop to determine
acceptability of the test, and look for upper airway
obstruction pattern.
Step 2. Look at the FEV1 to determine if it is normal (≥
80% predicted).
Step 3. Look at FVC to determine if it is within normal
limits (≥ 80%).
Step 4. Look at the FEV1/FVC ratio to determine if it is
within normal limits (≥ 70%).

Step 5. Look at FEF25-75% (Normal (≥ 60%)
• If FEV1, FEV1/FVC ratio, and FEF25-75% all are
normal, the patient has a normal PFT.
• If both FEV1 and FEV1/FVC are normal, but FEF2575% is ≤ 60% ,then think about early obstruction or
small airways obstruction.

• If FEV1 ≤ 80% and FEV1/FVC ≤ 70%, there is
obstructive defect, if FVC is normal, it is pure
obstruction. If FVC ≤ 80% , possibility of additional
restriction is there.
• If FEV1 ≤ 80% , FVC ≤ 80% and FEV1/FVC ≥ 70% ,
there is restrictive defect, get lung volumes to confirm.

Small Airways obstruction
• Diseases affecting primarily the small (peripheral)
airways can be extensive yet not affect the FEV1(e.g.
early COPD, interstitial granulomatous disorders).
• Small airways status is reflected by the FEF25-75%
(mid-range flow), best determined from the flowvolume loop.
• Some patients have normal spirometry with the
exception of a reduced FEF25-75%, this is
suggestive of possible small airways dysfunction and
potentially early obstruction.

Effect of Smoking:
• Smoking in patients with COPD is associated
with decline in FEV1 of 90-150 mL/year
• Smoking cessation is (associated with
increase in FEV1 for first year) followed with a
decline of only 30 mL/year

A. Intrinsic Restrictive Lung Disorders
1.
3.
4.

Sarcoidosis
Idiopathic pulmonary fibrosis
Interstitial pneumonitis
Tuberculosis

5.
6.

Pnuemonectomy (loss of lung)
Pneumonia

2.

B. Extrinsic Restrictive Lung Disorders
1.
2.
3.
4.
5.
6.
7.
8.

Scoliosis, Kyphosis
Ankylosing Spondylitis
Pleural Effusion
Pregnancy
Gross Obesity
Tumors
Ascites
Pain on inspiration - pleurisy, rib fractures

C. Neuromuscular Restrictive Lung
Disorders
1.
2.
3.
4.
5.
6.

Generalized Weakness – malnutrition
Paralysis of the diaphragm
Myasthenia Gravis
Muscular Dystrophy
Poliomyelitis
Amyotrophic Lateral Sclerosis

• Full expantion of the lung
is limited and therefore
the FVC is reduced
• FEV1 may be reduced
because the stiffness of
fibrotic lungs increases
the expiratory pressure
• FEV1/FVC will be Normal
or Increased
*if you suspect restrictive
pattern you must check
TLC

Flow volume loop in
Restrictive lung disease

Flow volume loop in
Restrictive lung disease :
 Full lung expantion is
prevented by fibrotic tissue in
the lung parenchyma and the
FVC is reduced .
 Elastic recoil may increased
by fibrotic tissue lead to
increase the airflow
 Both FEV1 and FVC may be
reduced because the lungs are
small and stiff ,but the peak
expiratory flow may be
preserved or even higher than
predicted leads to tall,narrow
and steep flow volume loop in
expiratory phase.

Obstructive & restrictive defects

Parameter
FEV1
FVC
FEV1/FVC

Obstruction
Reduced
Normal
Reduced

Restriction
Reduced
Reduced
Normal

A breathless 23-year-old woman has the
following lung function tests: FEV1 1.1L
(60%)/ FVC 1.3 L (55%)/ FEV1/FVC ratio =
84%/ TLC = 66% predicted/ RV = 57%
predicted/ TLCO = 55% predicted/ KCO =
110% predicted
What is the most likely diagnosis?
A : Acute sickle crisis
B : systemic lupus erythematosus (SLE)
pneumonitis
C : Scoliosis
D : Asthma
E : Cystic fibrosis.

C : Scoliosis
The lung function tests show a significant
restrictive defect. Only kyphoscoliosis or a
pneumonitis may fit this picture but given
the normal/high KCO (i.e. after correcting
for alveolar volumes), the most likely
answer is kyphoscoliosis as the gas
exchange after correcting for the alveolar
volume would in fact be high.

A 35 year old lady with systemic sclerosis
has breathlesness on exertion. She has
bilateral basal crepitations in the chests
and corresponding interstitial shadowing
on the CXR. Which is likely to be found on
her lung function tests?
A. P02 of 11 desaturating to 10 on exertion
B. FEV1 to FVC ratio of 65%
C. Diffusion capacity (DLCO) of 17
(predicted 23)
D. Increased residual volume
E. FEV1 of 5 L

c) diffusion capacity (DLCO) of 17
(predicted 23). A decrease in
diffusion capacity (DLCO)
indicates interstitial lung disease,
which is likely in a patient with
basal crepitations and a
predisposing connective tissue
disease

A 30 year old man has kyphoscoliosis
affecting his respiratory function. Which
one of the following is associated?
A. Inclusion body myositis
B. Genital ulceration
C. Klebsiella pneumonia
D. Pectus excavatum
E. Osteogenesis imperfecta

Answer: e) osteogenesis imperfecta.
Kyphoscoliosis occurs in :
Connective tissue disorders -osteogenesis imperfecta,
neurofibromatosis, Marfans
Neuromuscular disorders – poliomyelitis, Duchenne’s , Friedrich’s
ataxia, syringomyelia
Pulmonary disorders – Unilateral fibrosis, empyema,
pneumonectomy.
A restrictive defect occurs due to a reduction in FVC. Hypoxia is the
first consequence, later hypercapnia and cor pulmonale may occur.
Pectus excavatum is an inward chest wall deformity which may be
due to the pull of diaphragmatic fibres during development. It is
seldom symptomatic as is pectus carinatum, which is a protrusion
deformity due to skeletal overgrowth.

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