APM Welcome, APM North West Network Conference, Synergies Across Sectors
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1.
2. Definition
• Spirometry is a method of assessing lung
function by measuring the volume of air
that the patient is able to expel from the
lungs after a maximal inspiration.
• It is a reliable method of differentiating
between obstructive airways disorders
(e.g. COPD, asthma) and restrictive
diseases (where the size of the lungs is
reduced, e.g. fibrotic lung disease).
3. Indications
• To evaluate symptoms and signs of lung
disease (eg, cough, dyspnea, cyanosis,
wheezing, hyperinflation, hypoxemia,
hypercapnia)
• To assess the progression of lung
disease
• To monitor the effectiveness of therapy
• To evaluate preoperative patients in
selected situations.
4. • To screen people at risk of pulmonary
disease such as smokers or people
with occupational exposure to toxic
substances in occupational surveys.
• To monitor for the potentially toxic
effects of certain drugs or chemicals
(eg, amiodarone, beryllium)
• Measure airflow obstruction to help
make a definitive diagnosis of COPD
5. • Confirm presence of airway
obstruction
• Assess severity of airflow
obstruction
• Perform pre-employment screening
in certain professions.
• Assess the degree of disability.
6. NB:
Pulmonary function tests are
not otherwise indicated in patients
without symptoms, and they may be
confusing when nonpulmonary
diseases that affect the pulmonary
system are active (eg, congestive
heart failure).
7. Contraindications
If any of the following have occurred
recently, then it may be better to wait until
the patient has fully recovered before
carrying out spirometry.
• Haemoptysis of unknown origin
• Pneumothorax
• Unstable cardiovascular status, recent
myocardial infarction or pulmonary
embolism.
8. • Thoracic, abdominal or cerebral
aneurysms
• Recent eye surgery
• Acute disorders affecting test
performance, such as nausea or
vomiting
• Recent thoracic or abdominal surgical
procedures
• Current severe pain of the abdomen and
chest.
9.
10.
11. Definition
It is defined as the maximal amount of air
that can be exhaled forcefully after a maximal
inspiration or the most air a person can blow
out after taking the deepest possible breath.
13. FVC - forced vital capacity
• Defines maximum volume of exchangeable
air in lung (vital capacity) during forced
expiratory breathing maneuver. (approx. 4
liters)
• It requires muscular effort and some patient
training so slowly diminishes with normal
aging.
• Significantly reduced FVC suggests damage
to lung parenchyma e.g. fibrosis
14. FEV1
• Forced expiratory volume in the 1st sec:
• It is the volume of air exhaled during the
first second of a forced expiratory
maneuver.
– normal FEV1 about 3 liters
15. FEV1/FVC%
Definition:
– The value expresses the volume of air the
patient exhales in one second as a percent
of the total volume of air that is exhaled.
– Calculated by using largest valid FEV1 and
largest FVC even if they are not from the
same tracing.
• Find largest valid FEV1
• Find largest valid FVC
• Divide FEV1 by FVC
• Multiply by 100 to obtain percentage.
16. PEF - Peak Expiratory Flow rate
• Measures airflow limitations in large (central)
airways
• PEF measurements recommended for asthma
management
• PEF not recommend to evaluate patients for COPD
– cannot measure small airway airflow limitations
• Advantages of PEF tests
– Measurements within a minute (three short breaths)
– Uses simple, safe, low price, hand-held devices.
• Disadvantages of PEF tests (compared to
spirometry)
– Insensitive to obstruction of small airways (mild or early obstruction)
– PEF is very dependent on patient effort (large intra-subject variability)
– Mechanical PEF meters are much less accurate than spirometers
17. FEF25-75%
• Definition:
–The mean expiratory flow during the
middle half of the FVC
• More sensitive than FEV1.
• Considerably more variability than FVC
and FEV1.
• ATS recommends only be considered
after determining presence and clinical
severity of impairment and should not
be used to diagnosis disease in
individual patients
18. Ideal curve
It is characterized by:
1. An immediate vertical rise,
2. A sharp peak, and
3. A fairly smooth descent that returns to
zero flow.
19. 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
but may diagnose it
• Normal Spirometry doesn’t mean there is no
problem
Pulmonary vascular disease: Normal
spirometry but reduced TLCO
20. Technical feedback notes should be included by
operators on all spirometry reports and these
comments should be considered when
interpreting spirometry results
21. Types of ventilatory defects
Obstruction:
• Airflow limitation – unable to blow out quickly:
–reduced FEV1/FVC
e.g. asthma and/or COPD
–Reversibility: assesses improvement with therapy
–Reactive airways: abnormal airway hyper-responsiveness
(feature of asthma)
Restriction:
• Limitation to inspiration – small lungs
–Low FVC (and TLC)
e.g. fibrosis, pleural/chest wall disease, weak inspiratory muscles,
obesity
Mixed defect:
• Small lungs and unable to blow out quickly
–Low FEV1 and FEV1/FVC plus low FVC (and TLC)
22. The VC, FEV1, FEV1/VC ratio and
TLC are the basic parameters used to
properly interpret lung function.
FVC is often used in place of VC.
The FVC is usually reduced more than
SVC in airflow Obstruction.
23. FVC
• Interpretation of % predicted:
–80-120% Normal
–70-79% Mild reduction
–50%-69% Moderate reduction
–<50% Severe reduction
FVC
24. FEV1
• Interpretation of % predicted:
– >80 Mild obstruction
– 60-79 Moderate obstruction
– 50-59 Moderately severe obstruction
– 35-49 Severe obstruction
– <35 Very severe obstruction
FEV1 FVC
25. FEF25-75
• Interpretation of % predicted:
–>65% Normal
–45-65% Mild obstruction
–35-44% Moderate obstruction
–<35% Severe obstruction
26. Interpretation
• Use the FEV1/FVC ratio to detect obstruction
• Use FEV1 as % predicted to grade severity of obstruction
• Use FVC (or VC) to assess restriction
o Low FVC (VC) in presence of significant obstruction
does not necessarily indicate restriction
o Need to confirm and quantify restriction with
measurement of TLC
• A low FEF25–75% in the presence of normal FEV1 can be used
to detect ‘early’ airflow obstruction but only if FVC is within
normal limits.
• Lower limit of normal FEF25–75% is about 65% predicted
29. Assessment of
bronchodilator reversibility
Spirometry should be performed before and
after bronchodilator (whenever possible)
4 puffs (400ug) of salbutamol from MDI + spacer
wait 10 - 15 minutes for short acting β2-agonist
(salbutamol)
An increase in FEV1 of ≥ 12% and ≥ 200ml after
administration of a bronchodilator indicates
reversible airflow limitation consistent with
asthma.
30. Age: 47, Male, Height 163 cm; Weight
84 kg Caucasian
CLINICAL COMMENTS:
• Painter with recent SOBOE
• Night cough; symptomatically better on
weekends and holidays
• History of childhood rhinitis and asthma
• Nonsmoker
33. Restrictive Ventilatory Defects
(volume limiting)
In restrictive disorders there is a reduction in the overall lung
volume.Low FVC (and TLC)
This can be either intrapulmonary or extrapulmonary
• Intrapulmonary (increase in elastic recoil):
e.g. pulmonary fibrosis, alveolitis, edema, pneumoconioses
(e.g asbestosis) effects of drugs (amiodarone, methotrexate),
rheumatoid arthritis
• Intrapulmonary (reduction in volume):
e.g. tumours, lobectomy/pneumonectomy, pneumonia
• Extrapulmonary:
e.g. pleural effusion, thoracic cage deformity
(scoliosis),neuromuscular disorders obesity and pregnancy
35. Pulmonary Factors Can
Reduce Vital Capacity
• Loss of Distensible Tissue
– e.g. pneumonectomy, atelectasis.
• Decreased Compliance.
– e.g. respiratory distress syndrome, alveolar
edema, or infiltrative interstitial lung
diseases.
• Increased Residual Volume.
– e.g. emphysema, asthma, or lung cysts.
36. Extrapulmonary Factors Can
Reduce Vital Capacity
• Limited Thoracic Expansion.
– e.g. thoracic deformities (Kyphoscoliosis) and
pleural fibrosis.
• Limited Diaphragmatic Descent.
– e.g. ascites and pregnancy.
• Nerve or Muscle Dysfunction.
– Pain (surgery, rib fracture)
– Primary neuromuscular disease (e.g. Guillain-
Barré Syndrome).
37. FEF 25-75%
• What is it?
– Mean expiratory flow during middle half of FVC
maneuver
• What does it measure?
– Flow from airways that empty in the middle half of
FVC maneuver
• Is it a measure of small airways?
– Maybe in normals
– In asthma, or obstructive disease, it measures flow
from more obstructed airways which could be
small or larger with more obstruction
43. The static lung volumes can be measured
by a simple spirometer.
The inspiratory reserve volume (IRV) and
expiratory reserve volume (ERV) can be
calculated from such a tracing.
44. The functional residual capacity (FRC), the
volume of gas remaining in the lung at the end of a
quiet expiration, and the residual volume (RV),
the volume of gas remaining in the lung after a
maximal expiration, can be determined by one of
two methods:
1. Nitrogen Washout Method
2. Gas dilution tests. Dilutional: helium,
100% oxygen
3. Body plethysmography (Body Box).
45.
46. With the helium (He) dilution method [the
subject is connected, at the end of a quiet
expiration, to a closed spirometer
containing a known concentration and
volume of He, a gas that is almost
insoluble in blood.
After a period of equilibration, the
concentration of He in the lungs and the
spirometer stabilizes at a new level and
the FRC can be calculated
47. The most accurate way
The patient sits inside a fully enclosed
rigid box and breath through
mouthpiece connected through a
shutter to the internal volume of the
box
52. Obstructive Lung
Disease
Narrowing and closure of
airways during expiration
tends to lead to gas trapping
within the lungs and
hyperinflation of the chest.
Air trapping → increase in RV
Hyperinflation → increases TLC
RV tends to have a greater
percentage increase than TLC
RV/TLC ratio is therefore
increased (nl 20-35%)
Gas trapping may occur
without hyperinflation (increase
in RV & normal TLC)
53. Obstructive Lung Disease cont.
RV increased
TLC Nl/increased
RV/TLC increases
FRC increased
VC decreased
*Air trapping :Normal TLC with increase RV/TLC
*Hyperinflation: Increase in both TLC and RV/TLCl/
54.
55. Reduction in TLC is a cardinal
feature
1. In Intrinsic RLD (Interstitial Lung
Disease)
TLC will decrease
RV will decrease because of
increased stiffness of the lung
and loss of the alveoli.
Breathing take place at low
FRC because of the increased
effort needed to expand the
lung .
RV/TLC normal
56. 2. In extrinsic RLD
(chest wall disease :kyphoscoliosis
or neuromuscular disease)
TLC is reduced either
because of mechanical
limitation to chest wall
expansion or because of
respiratory muscle weakness
RV is Normal because Lung
tissue and elastic recoil is
normal So RV/TLC ratio will
be high
Breathing take place at low
FRC because of the
increased effort needed to
expand the lung .
57. Restrictive Lung Disease:
Extrinsic RLD
TLC decreased
RV normal
RV/TLC High
VC decreased
FRC decreased
RLD Intrinsic
TLC decreased
RV decreased
RV/TLC normal
FRC decreased
VC decreased
62. The process of carbon monoxide transfer from
the environment to the pulmonary capillary
blood includes five steps, as follows:
1. Flow of carbon monoxide to the airways and
alveolar spaces;
2. Mixing and diffusion of carbon monoxide in
the alveolar ducts, air sacs and alveoli;
3. Transfer of carbon monoxide across the
gaseous to liquid interface of the alveolar
membrane;
4. Mixing and diffusion of carbon monoxide in
the lung parenchyma and alveolar capillary
plasma;
5. Diffusion across the red-cell membrane and
within the interior of the red blood cell;
63. The process of carbon monoxide
uptake can be simplified into two
transfer or conductance
properties:
1. Membrane conductivity (DM),
which reflects the diffusion
properties of the alveolar
capillary membrane;
2. Binding of carbon monoxide and
Hb.
64. Diffusion limitations
• Distribution Transport to the alveoli
• Diffusion Transport through membrane
• Perfusion Transport through the
the blood plasma
to the hemoglobin
67. Single-breath testing technique
The single-breath determination of
DLCO involves measuring the uptake of
carbon monoxide from the lung over a
breath-holding period. To minimise
variability as much as possible, the
following specifications for the
standardisation of testing techniques
are provided.
68. Patient condition
Factors that affect VC:
Exercise ,
Body position,
Hb affinity for carbon monoxide,
Alveolar oxygen tension (PAO2),
Level of carboxyhaemoglobin
(COHb)) must be standardized.
69. If clinically acceptable,
The subject should not breathe
supplemental oxygen for ⩾10 min
prior to a DLCO manoeuvre.
In addition, when using exercise or
the supine position to assess the
ability of the lung to increase gas
transfer, the level of exercise and/or
the duration of the supine position
must be noted.
70. Subject must be seated comfortably
COHb produces an acute, reversible
decrease in DLCO, “anaemia effect”
from decreased Hb binding sites for
test gas carbon monoxide. As
cigarette smoking is the most
common source of COHb, subjects
must be asked to stop smoking or
other sources of carbon monoxide
exposure on the day of the test.
71. Inspired gas composition
The test gas should contain very
close to 0.3% carbon monoxide,
21% oxygen, a tracer gas and a
balance of nitrogen.
The tracer gas must be relatively
insoluble and relatively chemically
and biologically inert.
72. Its gaseous diffusivity should be
similar to carbon monoxide and it
should not interfere with the
measurement of carbon monoxide
concentration.
The tracer gas should also not
ordinarily be present in alveolar gas
or else be present at a known, fixed
concentration (e.g. argon).
73. Commonly used tracer gases include
helium and methane.
Helium meets most of the previous
criteria; however, its gaseous
diffusivity is considerably higher than
that of carbon monoxide.
Methane gaseous diffusivity is closer
to carbon monoxide but it has a
slightly higher liquid solubility than
helium.
No clinical difference in DLCO using
either helium or methane .
74.
75. Inspiratory maneuvers
Once the mouthpiece and nose clip
are in place, tidal breathing must be
carried out for a sufficient time to
assure that the subject is
comfortable with the mouthpiece
with no leaks.
The DLCO maneuver begins with
unforced exhalation to residual
volume (RV).
76. In obstructive lung disease, a
reasonable recommendation is that
this portion of the manoeuvre must
be limited to <12 s.
Submaximal inhalation occurs most
frequently in patients with airflow
obstruction who are not given
adequate time to exhale prior to the
inhalation of test gas.
77. At RV, the subject’s mouthpiece is
connected to a source of test gas, and the
subject inhales rapidly to TLC.
A submaximal inspired volume of test gas
(i.e. less than the known VC) can affect
carbon monoxide uptake depending upon
whether it is a result of an initial
suboptimal exhalation to RV (maneuver
performed at TLC) or whether it is due to
a suboptimal inhalation from RV
(maneuver performed below TLC).
78. Due to these effects, it is important
that the inspired volume of test gas,
VI, be as close to the known VC as
possible.
The inspiration must be rapid, since
the DLCO calculations assume
instantaneous lung filling .
Slower lung filling decreases the
amount of time the lung is at full
inspiration with a consequent
reduction in carbon monoxide
uptake.
79. Inspiration of test gas should be
sufficiently rapid such that 85% of VI
must be inspired in <4.0 s. If longer
inspiratory times are needed to
inspire 85% of VI, this must be
noted on the test report.
80. Breath-hold and expiratory
maneuvers
During the breath-hold, both the
Valsalva and Müller manoeuvres
(expiratory or inspiratory efforts
against a closed glottis, respectively)
can affect DLCO calculation by
decreasing or increasing thoracic
blood volume, respectively, resulting
in a corresponding decrease or
increase in DLCO, respectively, for
each maneuver.
81. The intrapulmonary pressure during
the breath-hold should thus be near
atmospheric and this is best
accomplished by having the subject
voluntarily maintain full inspiration
using only the minimal necessary
effort.
The breath-hold time must be 10±2
s, a target easily achieved in the vast
majority of subjects.
82. The expiratory maneuver must be
smooth, unforced and without
hesitation or interruption.
The exhalation time for washout and
discrete sample collection should not
exceed 4 s.
In subjects who require a longer
expiratory time to provide an
appropriate alveolar gas sample, the
expiratory time must be noted in the
test report.
83. Washout and sample collection
maneuvers
DLCO calculations are performed by
analysis of discrete alveolar gas
samples containing carbon monoxide
and tracer gas.
During expiration, a volume of gas
must be expired to clear the total
anatomical and equipment dead-
space volume (VD) and then
discarded before the alveolar sample
is collected.
84. Collecting an alveolar gas sample
before the point of dead-space
washout will underestimate DLCO, while
delaying sample collection beyond the
point of dead-space washout will
overestimate DLCO .
85. Maneuver intervals
The 2005 ERS/ATS recommendations
state that at least 4 min must be
allowed between maneuvers to allow
for adequate elimination of test gas
from the lungs.
The subject should remain seated
during this interval.
86. In patients with airflow obstruction, a
longer period (e.g. 10 min) should be
considered. Several deep inspirations
during this period may help to clear
test gases more effectively.
87. Parameters SB
Important parameters:
• DLCOSB transfer factor for CO
• VASB alveolar volume
• KCOSB Krogh factor ( = DLCOSB
/ VASB )
• RVSB-He residual volume
• TLCSB-He total lung capacity
88. Parameters SB
Important parameters:
HB hemoglobin
DLCOSB,c transfer factor for CO, HB-corrected
KCOSB,c Krogh factor, HB-corrected
VIN inspired volume
VDan anatomic dead space
89. Criteria for repeatability
At least two acceptable DLCO
measurements within 2 mL/min·mmHg
(0.67 mmol/min·kPa) of each other
90. DL
VA (He) # VA* VA (He) = VA*
Ventilatory
disturbance
1 2 3 4 5 6
Normal distrib.
of ventilation
Loss of
lung units
Loss of
functioning
lung units
Inhomo-
geneity of
ventilation:
additional
reduction
Anaemia Nonperfusion
of ventilated
alveoli
Alveolar
capillary
membrane
thickening
VA:
Alveolar
enlargemet
with
loss of gas
exchange
surface, e.g.
Emphysema
VA
DLCO / VA
normal DLCO / VA
Maldistribution
of ventilation
1 Abnormal
N2 washout
2 VA less than
80% of
measured TLC
1 Fewer binding
sites for CO
in plasma
2 More plasma
between
alveolar air and
binding sites
VA* = VA (ITGV) or VA (RB) according to He-washin (FRC-rebreathing)
No ventilatory
disturbance
Interpretation
91. DLCO Interpretation
Low DLCO with normal spirometry
– Pulmonary Vascular Disease
– Anaemia - correct for Hb
– Early ILDs or early emphysema
– Chronic pulmonary embolism
– Primary pulmonary hypertension
Low DLCO with restriction
– Interstitial Lung Disease
Low DLCO with obstruction
– Emphysema
– COPD
DO NOT USE DLCO/VA or KCO
Often Normal in Interstitial Lung Disease
92. Possible Causes of High DLCo
Intrapulmonary Haemorrhage
Asthma
Obesity ???
*DLCO is not always high in these patients
